Constant Current Led Driver

8/12/2019 Constant Current Led Driver

1/27

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F E A T U R E S D E S C R I P T I O N

A P P L I C A T I O N S

VIN

CTRL

SW

OVP

GND

L14.7 H

Rs

13

D1

Vin1.8 V to 6 V

FB

LED

RS

Enable/PWM Brightness Control100 Hz to 50 kHz

CO

100 nF

Cin4.7 F

3

5

6

4

8

7

1

2

T P S 6 1 0 4 2

S L V S 4 4 1 C D E C E M B E R 2 0 0 2 R E V I S E D M A R C H 2 0 0 7

C O N S T A N T C U R R E N T L E D D R I V E R

C u r r e n t S o u r c e W i t h O v e r v o l t a g e P r o t e c t i o n T h e T P S 6 1 0 4 2 i s a h i g h f r e q u e n c y b o o s t c o n v e r t e r w i t h c o n s t a n t c u r r e n t o u t p u t t h a t d r i v e s w h i t e L E D s I n p u t V o l t a g e R a n g e . . 1 . 8 V t o 6 V o r s i m i l a r . T h e L E D c u r r e n t i s s e t w i t h t h e e x t e r n a l I n t e r n a l 3 0 V S w i t c h s e n s e r e s i s t o r ( R S ) a n d i s d i r e c t l y r e g u l a t e d b y t h e

U p t o 8 5 % E f f i c i e n c y f e e d b a c k p i n ( F B ) t h a t r e g u l a t e s t h e v o l t a g e a c r o s s P r e c i s e B r i g h t n e s s C o n t r o l U s i n g P W M S i g n a l t h e s e n s e r e s i s t o r R S t o 2 5 2 m V ( t y p ) . T o c o n t r o l

L E D b r i g h t n e s s , t h e L E D c u r r e n t c a n b e p u l s e d b y o r A n a l o g S i g n a l a p p l y i n g a P W M ( p u l s e w i d t h m o d u l a t e d ) s i g n a l w i t h S w i t c h i n g F r e q u e n c y . . U p t o 1 M H z a f r e q u e n c y r a n g e o f 1 0 0 H z t o 5 0 k H z t o t h e c o n t r o l

I n t e r n a l P o w e r M O S F E T S w i t c h . . 5 0 0 m A p i n ( C T R L ) . T o a l l o w h i g h e r f l e x i b i l i t y , t h e d e v i c e c a n b e c o n f i g u r e d w h e r e t h e b r i g h t n e s s c a n b e c o n t r o l l e d O p e r a t e s W i t h S m a l l O u t p u t C a p a c i t o r s D o w n b y a n a n a l o g s i g n a l a s w e l l , a s d e s c r i b e d i n t h e t o 1 0 0 n F a p p l i c a t i o n i n f o r m a t i o n s e c t i o n . T o a v o i d p o s s i b l e

D i s c o n n e c t s L E D s D u r i n g S h u t d o w n l e a k a g e c u r r e n t s t h r o u g h t h e L E D s d u r i n g s h u t d o w n ,

N o L o a d Q u i e s c e n t C u r r e n t . . 3 8 A T y p t h e c o n t r o l p i n ( C T R L ) d i s a b l e s t h e d e v i c e a n d d i s c o n n e c t s t h e L E D s f r o m g r o u n d . F o r m a x i m u m S h u t d o w n C u r r e n t . . 0 . 1 A T y p s a f e t y d u r i n g o p e r a t i o n , t h e o u t p u t h a s i n t e g r a t e d A v a i l a b l e i n a S m a l l 3 m m 3 m m Q F N o v e r v o l t a g e p r o t e c t i o n t h a t p r e v e n t s d a m a g e t o t h e

P a c k a g e d e v i c e i n c a s e o f a h i g h i m p e d a n c e o u t p u t ( e . g . f a u l t y L E D ) .

W h i t e L E D S u p p l y f o r B a c k l i g h t / S i d e l i g h t D i s p l a y s

P D A , P o c k e t P C , S m a r t P h o n e s

H a n d h e l d D e v i c e s

C e l l u l a r P h o n e s

L a r g e r o u t p u t c a p a c i t o r v a l u e s l i k e 1 F a n d l a r g e r , r e d u c e t h e L E D r i p p l e c u r r e n t a n d i m p r o v e l i n e r e g u l a t i o n .

F i g u r e 1 . T y p i c a l A p p l i c a t i o n

P l e a s e b e a w a r e t h a t a n i m p o r t a n t n o t i c e c o n c e r n i n g a v a i l a b i l i t y , s t a n d a r d w a r r a n t y , a n d u s e i n c r i t i c a l a p p l i c a t i o n s o f T e x a s I n s t r u m e n t s s e m i c o n d u c t o r p r o d u c t s a n d d i s c l a i m e r s t h e r e t o a p p e a r s a t t h e e n d o f t h i s d a t a s h e e t .

P R O D U C T I O N D A T A i n f o r m a t i o n i s c u r r e n t a s o f p u b l i c a t i o n d a t e . C o p y r i g h t 2 0 0 2 2 0 0 7 , T e x a s I n s t r u m e n t s I n c o r p o r a t e d P r o d u c t s c o n f o r m t o s p e c i f i c a t i o n s p e r t h e t e r m s o f t h e T e x a s I n s t r u m e n t s s t a n d a r d w a r r a n t y . P r o d u c t i o n p r o c e s s i n g d o e s n o t

n e c e s s a r i l y i n c l u d e t e s t i n g o f a l l p a r a m e t e r s .
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A B S O L U T E M A X I M U M R A T I N G S

D I S S I P A T I O N R A T I N G

R E C O M M E N D E D O P E R A T I N G C O N D I T I O N S

T P S 6 1 0 4 2


O R D E R I N G I N F O R M A T I O N ( 1 )

T A P a c k a g e P a c k a g e M a r k i n g

4 0 t o 8 5 C T P S 6 1 0 4 2 D R B B H S

( 1 ) T h e D R B p a c k a g e i s a v a i l a b l e t a p e d a n d r e e l e d . A d d R s u f f i x ( T P S 6 1 0 4 2 D R B R ) t o o r d e r q u a n t i t i e s o f 3 0 0 0 d e v i c e s p e r r e e l . A d d T s u f f i x ( T P S 6 1 0 4 2 D R B T ) t o o r d e r q u a n t i t i e s o f 2 5 0 d e v i c e s p e r r e e l .

o v e r o p e r a t i n g f r e e - a i r t e m p e r a t u r e r a n g e ( u n l e s s o t h e r w i s e n o t e d ) ( 1 )

T P S 6 1 0 4 2

S u p p l y V o l t a g e s , v ( V I N ) ( 2 ) 0 . 3 V t o 7 V

V o l t a g e s , V ( R s ) , V ( C T R L ) , V ( F B ) 0 . 3 V t o V i n + 0 . 3 V

V o l t a g e s , V ( S W ) , V ( L E D ) ( 2 ) 3 0 V

V o l t a g e , V ( O V P ) 3 0 V

C o n t i n u o u s p o w e r d i s s i p a t i o n S e e D i s s i p a t i o n R a t i n g T a b l e

O p e r a t i n g j u n c t i o n t e m p e r a t u r e r a n g e 4 0 C t o 1 5 0 C

S t o r a g e t e m p e r a t u r e r a n g e , T S T G 6 5 C t o 1 5 0 C

L e a d t e m p e r a t u r e ( s o l d e r i n g , 1 0 s e c ) 2 6 0 C

( 1 ) S t r e s s e s b e y o n d t h o s e l i s t e d u n d e r a b s o l u t e m a x i m u m r a t i n g s m a y c a u s e p e r m a n e n t d a m a g e t o t h e d e v i c e . T h e s e a r e s t r e s s r a t i n g s o n l y , a n d f u n c t i o n a l o p e r a t i o n o f t h e d e v i c e a t t h e s e o r a n y o t h e r c o n d i t i o n s b e y o n d t h o s e i n d i c a t e d u n d e r r e c o m m e n d e d o p e r a t i n g c o n d i t i o n s i s n o t i m p l i e d . E x p o s u r e t o a b s o l u t e - m a x i m u m - r a t e d c o n d i t i o n s f o r e x t e n d e d p e r i o d s m a y a f f e c t d e v i c e r e l i a b i l i t y .

( 2 ) A l l v o l t a g e v a l u e s a r e w i t h r e s p e c t t o n e t w o r k g r o u n d t e r m i n a l .

P A C K A G E T A 2 5 C P O W E R D E R A T I N G F A C T O R T A = 7 0 C P O W E R T A = 8 5 C P O W E R R A T I N G A B O V E T A = 2 5 C R A T I N G R A T I N G

8 p i n Q F N ( 1 ) 3 7 0 m W 3 . 7 m W / C 2 0 4 m W 1 4 8 m W

( 1 ) T h e t h e r m a l r e s i s t a n c e j u n c t i o n t o a m b i e n t o f t h e 8 - p i n Q F N p a c k a g e i s 2 7 0 C / W . S t a n d a r d 2 - l a y e r P C B w i t h o u t v i a s f o r t h e t h e r m a l p a d . S e e t h e a p p l i c a t i o n s e c t i o n o n h o w t o i m p r o v e t h e t h e r m a l r e s i s t a n c e R J A .

M I N T Y P M A X U N I T

V I I n p u t v o l t a g e r a n g e 1 . 8 6 V

V s O u t p u t v o l t a g e r a n g e V I N 2 7 . 5 V

V S W S w i t c h v o l t a g e 3 0 V

I ( L E D ) M a x i m u m L E D s w i t c h c u r r e n t 6 0 m A

L I n d u c t o r ( 1 ) 4 . 7 H

f S w i t c h i n g f r e q u e n c y ( 1 ) 1 M H z

C I I n p u t c a p a c i t o r ( 1 ) 4 . 7 F

C O O u t p u t c a p a c i t o r ( 1 ) 1 0 0 n F

T A O p e r a t i n g a m b i e n t t e m p e r a t u r e 4 0 8 5 C

T J O p e r a t i n g j u n c t i o n t e m p e r a t u r e 4 0 1 2 5 C

( 1 ) S e e a p p l i c a t i o n s e c t i o n f o r f u r t h e r i n f o r m a t i o n

2 S u b m i t D o c u m e n t a t i o n F e e d b a c k
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E L E C T R I C A L C H A R A C T E R I S T I C S

T P S 6 1 0 4 2


VI = 3 . 6 V , C T R L = V I, TA = - 4 0 C t o + 8 5 C, t y p i c a l v a l u e s a r e a t T A = 2 5 C ( u n l e s s o t h e r w i s e n o t e d )

P A R A M E T E R T E S T C O N D I T I O N S M I N T Y P M A X U N I T

S u p p l y c u r r e n t

V I I n p u t v o l t a g e r a n g e 1 . 8 6 . 0 V

I( Q ) O p e r a t i n g q u i e s c e n t c u r r e n t i n t o V I N I O = 0 m A , n o t s w i t c h i n g 3 8 6 5 A I O ( s d ) S h u t d o w n c u r r e n t C T R L = G N D 0 . 1 1 A

V U V L O U n d e r - v o l t a g e l o c k o u t t h r e s h o l d V I f a l l i n g 1 . 5 1 . 7 V

C T R L

V I H C T R L h i g h l e v e l i n p u t v o l t a g e 1 . 3 V

V I L C T R L l o w l e v e l i n p u t v o l t a g e 0 . 3 V

II k g C T R L i n p u t l e a k a g e c u r r e n t C T R L = G N D o r V I N 0 . 1 A

to n M i n i m u m C T R L p u l s e w i d t h t o e n a b l e C T R L = l o w t o h i g h 5 0 u s

to f f M i n i m u m C T R L p u l s e w i d t h t o d i s a b l e C T R L = h i g h t o l o w 1 0 3 2 m s

f ( C T R L ) P W M s w i t c h i n g f r e q u e n c y a p p l i e d t o 0 . 1 5 0 k H z C T R L

D ( C T R L ) P W M d u t y c y c l e a p p l i e d t o C T R L 1 % 1 0 0 %

P o w e r s w i t c h a n d c u r r e n t l i m i t ( S W ) V S M a x i m u m s w i t c h v o l t a g e 3 0 V

r d s ( O N ) M O S F E T o n - r e s i s t a n c e V I = 3 . 6 V ; I ( S W ) = 2 0 0 m A 3 0 0 6 0 0 m

Il k g M O S F E T l e a k a g e c u r r e n t V ( S W ) = 2 8 V 0 . 1 1 0 A

IL I M M O F S E T c u r r e n t l i m i t 4 0 0 5 0 0 6 0 0 m A

L E D s w i t c h a n d c u r r e n t l i m i t ( L E D )

V S M a x i m u m s w i t c h v o l t a g e 3 0 V

r d s ( O N ) M O S F E T o n - r e s i s t a n c e V I = 3 . 6 V ; I S = 2 0 m A 1 2

Il k g M O S F E T l e a k a g e c u r r e n t V ( L E D ) = 2 8 V 0 . 1 1 0 A

O u t p u t

V O O u t p u t v o l t a g e r a n g e V I 2 7 . 5 V

I ( F B ) F e e d b a c k i n p u t b i a s c u r r e n t ( 1 ) V ( F B ) = 0 . 2 5 2 V 1 0 0 n A

V F B F e e d b a c k t r i p p o i n t v o l t a g e 1 . 8 V V I 6 V 2 4 4 2 5 2 2 6 0 m V

V ( O V P ) O u t p u t o v e r v o l t a g e p r o t e c t i o n V O r i s i n g 2 7 . 5 2 9 3 0 V

V h y s ( O V P ) O u t p u t o v e r v o l t a g e p r o t e c t i o n h y s t e r e s i s 5 7 V

I ( O V P ) O V P i n p u t c u r r e n t V O = 1 5 V 9 1 2 A

( 1 ) T h e f e e d b a c k i n p u t i s h i g h i m p e d a n c e M O S F E T G a t e i n p u t .

3S u b m i t D o c u m e n t a t i o n F e e d b a c k


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SW8

OVP7

GND6

CTRL5

LED

DRB PACKAGE

(TOP VIEW)

1

RS 2

VIN 3

FB 4

Exposed

ThermalDie Pad

T P S 6 1 0 4 2


T h e e x p o s e d t h e r m a l d i e p a d i s c o n n e c t e d t o G N D .

T e r m i n a l F u n c t i o n s

T E R M I N A L N A M E N O . I / O D E S C R I P T I O N

C o m b i n e d e n a b l e a n d P W M c o n t r o l p i n . I f C T R L i s c o n s t a n t l y p u l l e d h i g h , t h e d e v i c e i s e n a b l e d a n d t h e C T R L 5 I i n t e r n a l L E D s w i t c h ( Q 2 ) i s c o n s t a n t l y t u r n e d o n . W h e n C T R L i s p u l l e d t o G N D , t h e d e v i c e i s d i s a b l e d .

A p p l y a P W M s i g n a l ( 1 0 0 H z t o 5 0 k H z ) t o t h i s p i n t o c o n t r o l t h e b r i g h t n e s s o f t h e L E D s

F B 4 I F e e d b a c k . F B r e g u l a t e s t h e L E D c u r r e n t t h r o u g h t h e s e n s e r e s i s t o r b y r e g u l a t i n g t h e v o l t a g e a c r o s s R S t o2 5 2 m V .

G N D 6 G N D

L E D 1 I I n p u t o f t h e L E D s w i t c h ( Q 2 ) . C o n n e c t t h e L E D s t o t h i s p i n .

O V P 7 I O v e r v o l t a g e p r o t e c t i o n . O V P i s c o n n e c t e d t o t h e o u t p u t c a p a c i t o r o f t h e c o n v e r t e r .

R S 2 O O u t p u t o f t h e i n t e r n a l L E D s w i t c h . T h e s e n s e r e s i s t o r t h a t p r o g r a m s t h e L E D c u r r e n t i s c o n n e c t e d t o R S .

S W 8 I D r a i n o f t h e i n t e g r a t e d s w i t c h ( Q 1 )

V I N 3 I I n p u t s u p p l y p i n .



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UVLO

Bias

+

+

CTRL

EN

VREF

0.252 V

Thermal

Shutdown

Control

Logic

EN

Gate

Driver

VIN

OVP

SW

R1

2 M

R2

30 k

Current

LimitSoftstart

6 s Max

On Time

Overvoltage Protection

0.4 V

Enable

Control

Logic

EN

PWM

Gate

DriveGND

FB

Error

Comparator

VREF

400 ns Min

Off Time

Q1

Q2

LED

RS

T P S 6 1 0 4 2


F U N C T I O N A L B L O C K D I A G R A M

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T Y P I C A L C H A R A C T E R I S T I C S

70

72

74

76

78

80

82

84

86

88

1 2 3 4 5 6

Efficiency%

4 LEDs 13 V, CO= 1 F

VI Input Voltage V

IO= 15 mA

70

72

74

76

78

80

82

84

86

88

90

0.1 1 10 100

IO Output Current mA

Efficiency%

4 LEDs 13 V, CO= 1 F

VI= 4.2V

VI= 3.6V

VI= 2.4V

T P S 6 1 0 4 2


T a b l e o f G r a p h s

F I G U R E

v s L E D c u r r e n t F i g u r e 2 E f f i c i e n c y

v s I n p u t v o l t a g e F i g u r e 3

IQ O p e r a t i n g Q u i e s c e n t C u r r e n t i n t o V I N v s I n p u t v o l t a g e a n d T e m p e r a t u r e F i g u r e 4

V ( F B ) F e e d b a c k v o l t a g e v s T e m p e r a t u r e F i g u r e 5

I ( F B ) F e e d b a c k c u r r e n t v s T e m p e r a t u r e F i g u r e 6

v s T e m p e r a t u r e F i g u r e 7 M a i n s w i t c h Q 1

v s I n p u t v o l t a g e F i g u r e 8 r d s ( o n )

v s T e m p e r a t u r e F i g u r e 9 L E D s w i t c h Q 2

v s I n p u t v o l t a g e F i g u r e 1 0

IL E D A v e r a g e L E D c u r r e n t v s P W M d u t y c y c l e o n C T R L p i n F i g u r e 1 1

S o f t s t a r t F i g u r e 1 2

P F M o p e r a t i o n ( f i x e d p e a k c u r r e n t c o n t r o l ) F i g u r e 1 3

B u r s t m o d e o p e r a t i o n ( f i x e d p e a k c u r r e n t F i g u r e 1 4 c o n t r o l )

P W M d i m m i n g F i g u r e 1 5

E f f i c i e n c y E f f i c i e n c y v s v s

L E D C u r r e n t I n p u t V o l t a g e

F i g u r e 2 . F i g u r e 3 .



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VI- Input Voltage - V

0

5

10

15

20

25

3035

40

45

50

1.8 2.4 3.0 3.6 4.2 4.8 5.4 6.0

QuiescentCurrentinto

VI/A

TA= 25C

TA= -40C

TA= 85C

TA- Free-Air Temperature - C

240

242

244

246

248

250

252254

256

258

260

-40 -15 10 35 60 85

V(fb)-FeedbackVoltag

e-mV VCC= 3.7 V


-60

-40

-20

0

20

40

60

-40 -15 10 35 60 85

I(fb)-FeedbackCurrent-nA

VCC= 3.6 V

VCC= 2.4 VVCC= 5 V

200

250

300

350

400

450

500

40 15 10 35 60 85

TA Free-Air Temperature C

rds(on)

On-StateResistancem VCC= 3.6 V

0

100

200

300

400

500

600

1.8 2.4 3.0 3.6 4.2 4.8 5.4 6.0

VI Input Voltage V

rds(on)

On

-StateResistancem TA= 27C

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4

1.5

1.6

-40 -15 10 35 60 85


rds(on)-O

n-StateResistance- VCC= 3.6 V

T P S 6 1 0 4 2


O p e r a t i n g Q u i e s c e n t C u r r e n t i n t o V I N F e e d b a c k V o l t a g e v s v s

I n p u t V o l t a g e a n d T e m p e r a t u r e T e m p e r a t u r e

F i g u r e 4 . F i g u r e 5 .

F e e d b a c k C u r r e n t r d s ( o n ) M a i n S w i t c h ( Q 1 )

v s v s T e m p e r a t u r e T e m p e r a t u r e

F i g u r e 6 . F i g u r e 7 .

r d s ( O N ) M a i n S w i t c h ( Q 1 ) r d s ( o n ) L E D S w i t c h ( Q 2 ) v s v s

I n p u t V o l t a g e T e m p e r a t u r e

F i g u r e 8 . F i g u r e 9 .



8/27

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0.0

0.5

1.0

1.5

2.0

2.5

3.0

1.8 2.4 3.0 3.6 4.2 4.8 5.4 6.0

VI- Input Voltage - V

rds(on)-On-StateResistance- TA= 25C

0

5

10

15

20

0 20 40 60 80 100

Duty Cycle - %

IO-

OutputCurrent-mA

fPWM= 100 Hz fPWM= 50 kHz

fPWM= 25 kHz

50s/Div

Vout10V/Div

CTRL

1V/Div

Input Current

100mA/Div

2.5s/Div

Vsw

5V/Div

LED Current

20mA/Div

Vout

500mV/Div

2.5s/Div

Vsw

5V/Div

LED Current

20mA/Div

Vout

50mV/Div

25s/Div

Vsw

5V/Div

LED Current

20mA/Div

Vout

500mV/Div

T P S 6 1 0 4 2


r d s ( o n ) L E D S w i t c h ( Q 2 ) A v e r a g e L E D C u r r e n t v s v s

I n p u t V o l t a g e P W M D u t y C y c l e o n C T R L P i n

F i g u r e 1 0 . F i g u r e 1 1 .

S o f t s t a r t P F M O p e r a t i o n

F i g u r e 1 2 . F i g u r e 1 3 .

B u s t M o d e O p e r a t i o n P W M D i m m i n g

F i g u r e 1 4 . F i g u r e 1 5 .



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D E T A I L E D D E S C R I P T I O N

O p e r a t i o n

B o o s t C o n v e r t e r

P e a k C u r r e n t C o n t r o l ( B o o s t C o n v e r t e r )

IP(typ)

I(LIM)

VI

L 100 ns

IP(typ)

500 mAV

IL 100 ns

S o f t s t a r t

T P S 6 1 0 4 2


T h e T P S 6 1 0 4 2 o p e r a t e s l i k e a s t a n d a r d b o o s t c o n v e r t e r b u t r e g u l a t e s t h e v o l t a g e a c r o s s t h e s e n s e r e s i s t o r ( R S )i n s t e a d o f t h e o u t p u t v o l t a g e . T h i s g i v e s a n a c c u r a t e r e g u l a t e d L E D c u r r e n t i n d e p e n d e n t o f t h e i n p u t v o l t a g e a n dn u m b e r o f L E D s c o n n e c t e d . W i t h i n t e g r a t e d o v e r v o l t a g e p r o t e c t i o n ( O V P ) t h e T P S 6 1 0 4 2 i s c o n f i g u r e d a s a c u r r e n t s o u r c e w i t h o v e r v o l t a g e p r o t e c t i o n i d e a l l y s u i t e d t o d r i v e L E D s . W i t h t h e 3 0 V i n t e r n a l s w i t c h , t h e d e v i c e c a n g e n e r a t e o u t p u t v o l t a g e s o f u p t o 2 7 . 5 V a n d h a s a n i n t e r n a l 5 0 0 m A M O S F E T s w i t c h ( Q 1 ) . T h i s a l l o w s s e v e r a l L E D s t o b e c o n n e c t e d i n s e r i e s t o t h e o u t p u t . T h e i n t e r n a l L E D s w i t c h ( Q 2 ) i n s e r i e s w i t h t h e L E D s h a s a m a x i m u m c u r r e n t r a t i n g o f 6 0 m A a n d d i s c o n n e c t s t h e L E D s f r o m g r o u n d d u r i n g s h u t d o w n . T h e L E D s w i t c h i s d r i v e n b y a P W M s i g n a l a p p l i e d t o t h e c o n t r o l p i n ( C T R L ) , w h i c h d i r e c t l y c o n t r o l s t h e L E D b r i g h t n e s s . W i t h t h i s c o n t r o l m e t h o d t h e L E D b r i g h t n e s s d e p e n d s o n t h e P W M d u t y c y c l e o n l y a n d i s i n d e p e n d e n t o f t h e P W M f r e q u e n c y a n d a m p l i t u d e .

T h e b o o s t c o n v e r t e r o p e r a t e s i n a p u l s e f r e q u e n c y m o d u l a t i o n ( P F M ) s c h e m e w i t h c o n s t a n t p e a k c u r r e n t c o n t r o l . T h i s c o n t r o l s c h e m e m a i n t a i n s h i g h e f f i c i e n c y o v e r t h e e n t i r e l o a d c u r r e n t r a n g e a n d w i t h a s w i t c h i n g f r e q u e n c y o f u p t o 1 M H z , e n a b l e s t h e u s e o f s m a l l e x t e r n a l c o m p o n e n t s . T h e c o n v e r t e r m o n i t o r s t h e s e n s e v o l t a g e a c r o s s R S w i t h t h e f e e d b a c k p i n ( F B ) a n d , w h e n t h e f e e d b a c k v o l t a g e f a l l s b e l o w t h e r e f e r e n c e v o l t a g e ( 2 5 2 m V t y p ) ,

t h e m a i n s w i t c h t u r n s o n a n d t h e c u r r e n t r a m p s u p . T h e m a i n s w i t c h t u r n s o f f w h e n t h e i n d u c t o r c u r r e n t r e a c h e s t h e i n t e r n a l l y s e t p e a k c u r r e n t o f 5 0 0 m A ( t y p ) . R e f e r t o t h e p e a k c u r r e n t c o n t r o l s e c t i o n f o r m o r e i n f o r m a t i o n . T h e s e c o n d c r i t e r i a t h a t t u r n s o f f t h e m a i n s w i t c h i s t h e m a x i m u m o n - t i m e o f 6 s ( t y p ) . T h i s l i m i t s t h e m a x i m u m o n - t i m e o f t h e c o n v e r t e r i n e x t r e m e c o n d i t i o n s . A s t h e s w i t c h i s t u r n e d o f f t h e e x t e r n a l S c h o t t k y d i o d e i s f o r w a r d b i a s e d , d e l i v e r i n g t h e s t o r e d i n d u c t o r e n e r g y t o t h e o u t p u t . T h e m a i n s w i t c h r e m a i n s o f f u n t i l t h e m i n i m u m o f f t i m e o f 4 0 0 n s ( t y p ) h a s p a s s e d a n d t h e f e e d b a c k v o l t a g e i s b e l o w t h e r e f e r e n c e v o l t a g e a g a i n . U s i n g t h i s P F M p e a k c u r r e n t c o n t r o l s c h e m e , t h e c o n v e r t e r o p e r a t e s i n d i s c o n t i n u o u s c o n d u c t i o n m o d e ( D C M ) w h e r e t h e s w i t c h i n g f r e q u e n c y d e p e n d s o n t h e i n d u c t o r , i n p u t a n d o u t p u t v o l t a g e , a n d L E D c u r r e n t . L o w e r L E D c u r r e n t s r e d u c e t h e s w i t c h i n g f r e q u e n c y , w h i c h r e s u l t s i n h i g h e f f i c i e n c y o v e r t h e e n t i r e L E D c u r r e n t r a n g e . T h i s r e g u l a t i o n s c h e m e i s i n h e r e n t l y s t a b l e , a l l o w i n g a w i d e r a n g e f o r t h e s e l e c t i o n o f t h e i n d u c t o r a n d o u t p u t c a p a c i t o r .

T h e i n t e r n a l s w i t c h i s t u r n e d o n u n t i l t h e i n d u c t o r c u r r e n t r e a c h e s t h e D C c u r r e n t l i m i t ( I L I M ) o f 5 0 0 m A ( t y p ) . D u e t o t h e i n t e r n a l c u r r e n t l i m i t d e l a y o f 1 0 0 n s ( t y p ) t h e a c t u a l c u r r e n t e x c e e d s t h e D C c u r r e n t l i m i t t h r e s h o l d b y a s m a l l a m o u n t . T h e t y p i c a l p e a k c u r r e n t l i m i t c a n b e c a l c u l a t e d :

T h e h i g h e r t h e i n p u t v o l t a g e a n d t h e l o w e r t h e i n d u c t o r v a l u e , t h e g r e a t e r t h e c u r r e n t l i m i t o v e r s h o o t .

A l l i n d u c t i v e s t e p - u p c o n v e r t e r s e x h i b i t h i g h i n - r u s h c u r r e n t d u r i n g s t a r t - u p i f n o s p e c i a l p r e c a u t i o n s a r e t a k e n .

T h i s c a n c a u s e v o l t a g e d r o p s a t t h e i n p u t r a i l d u r i n g s t a r t - u p , w h i c h m a y r e s u l t i n a n u n w a n t e d o r p r e m a t u r e s y s t e m s h u t d o w n .

T h e T P S 6 1 0 4 2 l i m i t s t h i s i n - r u s h c u r r e n t d u r i n g s t a r t - u p b y i n c r e a s i n g t h e c u r r e n t l i m i t i n t w o s t e p s s t a r t i n g f r o m IL I M / 4 f o r 2 5 6 s w i t c h c y c l e s t o I L I M / 2 f o r t h e n e x t 2 5 6 s w i t c h c y c l e s a n d t h e n f u l l c u r r e n t l i m i t . S e e F i g u r e 1 2 f o rt y p i c a l s t a r t - u p b e h a v i o r .



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C o n t r o l ( C T R L )

t

ton

Low

High

tp

D = tp/t

ton

toff

Minimum

On-Time

to Enable

the Device

(50 s)

Minimum

Off-Time

to Disable

the Device

(32 ms)

A p p l y i n g a P W M S i g n a l t o t h e C T R L P i n w i t h a n O n - T i m e t p 2 . 5 s

T P S 6 1 0 4 2


D E T A I L E D D E S C R I P T I O N ( c o n t i n u e d )

T h e C T R L p i n s e r v e s t w o f u n c t i o n s . O n e i s t h e e n a b l e a n d d i s a b l e o f t h e d e v i c e . T h e o t h e r i s t h e P W M c o n t r o l o f t h e i n t e r n a l L E D s w i t c h ( Q 2 ) . I f n o P W M s i g n a l i s a p p l i e d t o t h e C T R L p i n , t h e n t h e C T R L p i n c a n b e u s e d a s a s t a n d a r d e n a b l e p i n f o r t h e d e v i c e . T o e n a b l e t h e d e v i c e , t h e C T R L p i n m u s t b e p u l l e d h i g h f o r t i m e p e r i o d o f

a t l e a s t 5 0 s . T h e d e v i c e s t a r t s w i t h t h e S o f t s t a r t c y c l e . P u l l i n g t h e C T R L p i n t o G N D f o r a t i m e p e r i o d 3 2 m s d i s a b l e s t h e d e v i c e , d i s c o n n e c t i n g t h e L E D s f r o m G N D b y o p e n i n g t h e L E D s w i t c h ( Q 2 ) t o a v o i d a n y L E D l e a k a g e c u r r e n t . S e e F i g u r e 1 6 f o r t h e C T R L p i n t i m i n g .

T h e i n t e r n a l L E D s w i t c h ( Q 2 ) i s d r i v e n b y t h e P W M s i g n a l w h e n a p p l i e d t o t h e C T R L p i n . A p p l y i n g a P W M s i g n a l i n t h e r a n g e o f 1 0 0 H z t o 5 0 k H z a l l o w s t h e L E D c u r r e n t t o b e p u l s e d w i t h t h e d u t y c y c l e o f t h e P W M s i g n a l . T h e C T R L p i n a c c e p t s a P W M d u t y c y c l e f r o m D = 1 % t o 1 0 0 % . D u t y c y c l e s b e l o w 1 % a r e a l s o p o s s i b l e w i t h t h e r e s t r i c t i o n t h a t t h e d e v i c e i s f o r c e d i n t o s h u t d o w n a s t h e o f f t i m e o f t h e a p p l i e d P W M s i g n a l e x c e e d s 1 0 m s .

W h e n a P W M s i g n a l i s a p p l i e d t o t h e C T R L p i n t h e L E D s w i t c h ( Q 2 ) t u r n s o n i m m e d i a t e l y . T h e i n t e r n a l e r r o r c o m p a r a t o r i s d i s a b l e d f o r 4 0 0 n s . T h i s 4 0 0 n s d e l a y t i m e i s r e q u i r e d t o e s t a b l i s h t h e c o r r e c t v o l t a g e l e v e l a c r o s s t h e s e n s e r e s i s t o r R S a f t e r t h e L E D s w i t c h ( Q 2 ) i s c l o s e d .

T o a c h i e v e g o o d L E D c u r r e n t a c c u r a c y a n d l i n e a r i t y , t h e s w i t c h i n g f r e q u e n c y o f t h e c o n v e r t e r m u s t b e h i g h e r t h a n t h e P W M f r e q u e n c y a p p l i e d t o t h e C T R L p i n .

F i g u r e 1 6 . C T R L T i m i n g D i a g r a m

T h e C T R L t i m i n g d i a g r a m i s s h o w n i n F i g u r e 1 6 . T o e n a b l e t h e d e v i c e , t h e C T R L s i g n a l m u s t b e h i g h f o r 5 0 s . T h e P W M s i g n a l c a n t h e n b e a p p l i e d w i t h a p u l s e w i d t h ( t p ) g r e a t e r o r s m a l l e r t h a n t O N . T o f o r c e t h e d e v i c e i n t o s h u t d o w n m o d e , t h e C T R L s i g n a l m u s t b e l o w f o r a t l e a s t 3 2 m s . R e q u i r i n g t h e C T R L p i n t o b e l o w f o r 3 2 m S b e f o r e t h e d e v i c e e n t e r s s h u t d o w n a l l o w s f o r P W M d i m m i n g f r e q u e n c i e s a s l o w a s 1 0 0 H z . T h e d e v i c e i s e n a b l e d a g a i n w h e n a C T R L s i g n a l i s h i g h f o r a p e r i o d o f 5 0 s m i n i m u m . S e e F i g u r e 1 1 f o r t h e P W M d u t y c y c l e v e r s u s L E D c u r r e n t c h a r a c t e r i s t i c .

T h i s C T R L p i n m u s t b e t e r m i n a t e d .

I n s u c h a c a s e t h e o n - t i m e o f t h e P W M s i g n a l , t p , m u s t b e > 2 . 5 s u n t i l t h e s o f t s t a r t i s c o m p l e t e d . T h e s o f t s t a r t i s c o m p l e t e d a f t e r 5 1 2 s w i t c h i n g c y c l e s . T o s i m p l y , e s t i m a t e t h e s o f t s t a r t t i m e , m u l t i p l y t h e p e r i o d o f t h e P W M s i g n a l t i m e s 5 1 2 , a n d a d d 5 0 s t o i t . F o r a 5 0 - k H z s i g n a l t h i s w o u l d b e 1 0 . 3 m s a s a m i n i m u m s o f t s t a r t t i m e p e r i o d . A f t e r t h e s o f t s t a r t t i m e i s c o m p l e t e d t h e P W M o n t i m e c a n b e r e d u c e d t o t p > 4 0 0 n s .

1 0 S u b m i t D o c u m e n t a t i o n F e e d b a c k
http://www.go-dsp.com/forms/techdoc/doc_feedback.htm?litnum=SLVS441C&partnum=TPS61042http://www.go-dsp.com/forms/techdoc/doc_feedback.htm?litnum=SLVS441C&partnum=TPS61042http://focus.ti.com/docs/prod/folders/print/tps61042.html


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O v e r v o l t a g e P r o t e c t i o n ( O V P )

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D E T A I L E D D E S C R I P T I O N ( c o n t i n u e d )

A s w i t h a n y c u r r e n t s o u r c e , t h e o u t p u t v o l t a g e r i s e s a s t h e o u t p u t i m p e d a n c e i n c r e a s e s o r i s d i s c o n n e c t e d . T o p r e v e n t t h e o u t p u t v o l t a g e f r o m e x c e e d i n g t h e m a x i m u m m a i n s w i t c h ( Q 1 ) v o l t a g e r a t i n g o f 3 0 V , a n o v e r v o l t a g e p r o t e c t i o n c i r c u i t i s i n t e g r a t e d . W h e n t h e o u t p u t v o l t a g e e x c e e d s t h e O V P t h r e s h o l d v o l t a g e , ( Q 1 ) t u r n s o f f . T h e

c o n v e r t e r s w i t c h r e m a i n s o f f u n t i l t h e o u t p u t v o l t a g e f a l l s b e l o w t h e O V P t h r e s h o l d v o l t a g e . A s l o n g a s t h e o u t p u t v o l t a g e i s b e l o w t h e O V P t h r e s h o l d t h e c o n v e r t e r c o n t i n u e s i t s n o r m a l o p e r a t i o n , u n t i l t h e o u t p u t v o l t a g e e x c e e d s t h e O V P t h r e s h o l d a g a i n .

A n u n d e r v o l t a g e l o c k o u t f e a t u r e p r e v e n t s m i s - o p e r a t i o n o f t h e d e v i c e a t i n p u t v o l t a g e s b e l o w 1 . 5 V ( t y p ) . A s l o n g a s t h e i n p u t v o l t a g e i s b e l o w t h e u n d e r v o l t a g e t h r e s h o l d t h e d e v i c e r e m a i n s o f f , w i t h t h e m a i n M O S F E T s w i t c h ( Q 1 ) a n d t h e L E D s w i t c h ( Q 2 ) o p e n .

A n i n t e r n a l t h e r m a l s h u t d o w n i s i m p l e m e n t e d i n t h e T P S 6 1 0 4 2 t h a t s h u t s d o w n t h e d e v i c e i f t h e t y p i c a l j u n c t i o n t e m p e r a t u r e o f 1 6 0 C i s e x c e e d e d . I f t h e d e v i c e i s i n t h e r m a l s h u t d o w n m o d e , t h e m a i n M O S F E T s w i t c h ( Q 1 ) a n d t h e L E D s w i t c h ( Q 2 ) a r e o p e n .

1 1S u b m i t D o c u m e n t a t i o n F e e d b a c k


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A P P L I C A T I O N I N F O R M A T I O N

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T P S 6 1 0 4 2


T h e P F M p e a k c u r r e n t c o n t r o l s c h e m e o f t h e T P S 6 1 0 4 2 i s i n h e r e n t l y s t a b l e . T h e i n d u c t o r v a l u e d o e s n o t a f f e c t t h e s t a b i l i t y o f t h e r e g u l a t o r . T h e s e l e c t i o n o f t h e i n d u c t o r t o g e t h e r w i t h t h e n o m i n a l L E D c u r r e n t , i n p u t , a n d o u t p u t v o l t a g e o f t h e a p p l i c a t i o n d e t e r m i n e s t h e s w i t c h i n g f r e q u e n c y o f t h e c o n v e r t e r .

T h e f i r s t s t e p i s t o c a l c u l a t e t h e m a x i m u m l o a d c u r r e n t t h e c o n v e r t e r c a n s u p p o r t u s i n g t h e s e l e c t e d i n d u c t o r . T h e i n d u c t o r v a l u e h a s l e s s e f f e c t o n t h e m a x i m u m a v a i l a b l e l o a d c u r r e n t a n d i s o n l y o f s e c o n d a r y o r d e r . A g o o d i n d u c t o r v a l u e t o s t a r t w i t h i s 4 . 7 H . D e p e n d i n g o n t h e a p p l i c a t i o n , i n d u c t o r v a l u e s d o w n t o 1 . 0 H c a n b e u s e d . T h e m a x i m u m i n d u c t o r v a l u e i s d e t e r m i n e d b y t h e m a x i m u m o n t i m e o f t h e s w i t c h o f 6 s ( t y p ) . T h e p e a k c u r r e n t l i m i t o f 5 0 0 m A ( t y p ) m u s t b e r e a c h e d w i t h i n t h i s 6 s f o r p r o p e r o p e r a t i o n . T h e m a x i m u m l o a d c u r r e n t o f t h e c o n v e r t e r i s d e t e r m i n e d a t t h e o p e r a t i o n p o i n t w h e r e t h e c o n v e r t e r s t a r t s t o e n t e r t h e c o n t i n u o u s c o n d u c t i o n m o d e . T h e c o n v e r t e r m u s t a l w a y s o p e r a t e i n d i s c o n t i n u o u s c o n d u c t i o n m o d e t o m a i n t a i n r e g u l a t i o n .

D e p e n d i n g o n t h e t i m e p e r i o d o f t h e i n d u c t o r c u r r e n t f a l l t i m e b e i n g l a r g e r o r s m a l l e r c o m p a r e d t o t h e m i n i m u m o f f t i m e o f t h e c o n v e r t e r ( 4 0 0 n s t y p ) , t h e m a x i m u m l o a d c u r r e n t c a n b e c a l c u l a t e d .

I n d u c t o r f a l l t i m e :

F o r t f a l l 4 0 0 n s

f o r t f a l l 4 0 0 n s

w i t h :

L = s e l e c t e d i n d u c t o r v a l u e

= e x p e c t e d c o n v e r t e r e f f i c i e n c y . T y p i c a l l y b e t w e e n 7 0 % t o 8 5 %

( P e a k i n d u c t o r c u r r e n t a s d e s c r i b e d i n t h e p e a k c u r r e n t c o n t r o l s e c t i o n )

T h e a b o v e f o r m u l a c o n t a i n s t h e e x p e c t e d c o n v e r t e r e f f i c i e n c y t h a t a l l o w s c a l c u l a t i n g t h e e x p e c t e d m a x i m u m l o a d c u r r e n t t h e c o n v e r t e r c a n s u p p o r t . T h e e f f i c i e n c y c a n b e t a k e n o u t o f t h e e f f i c i e n c y g r a p h s s h o w n i n F i g u r e 2 a n d F i g u r e 3 o r 8 0 % c a n b e u s e d a s a n a c c u r a t e e s t i m a t i o n .

I f t h e c o n v e r t e r c a n s u p p o r t t h e d e s i r e d L E D c u r r e n t , t h e n e x t s t e p i s t o c a l c u l a t e t h e c o n v e r t e r s w i t c h i n g f r e q u e n c y a t t h e o p e r a t i o n p o i n t , w h i c h m u s t b e 1 M H z . A l s o t h e c o n v e r t e r s w i t c h i n g f r e q u e n c y s h o u l d b e m u c h h i g h e r t h a n t h e a p p l i e d P W M f r e q u e n c y a t t h e C T R L p i n t o a v o i d n o n - l i n e a r b r i g h t n e s s c o n t r o l . A s s u m i n g t h e c o n v e r t e r s h o w s n o d o u b l e p u l s e s o r p u l s e b u r s t s ( F i g u r e 1 3 , F i g u r e 1 4 ) o n t h e s w i t c h n o d e ( S W ) t h e s w i t c h i n g f r e q u e n c y a t t h e o p e r a t i o n p o i n t c a n b e c a l c u l a t e d a s :

w i t h :

I ( L I M ) = m i n i m u m s w i t c h c u r r e n t l i m i t ( 5 0 0 m A t y p )


I ( L O A D ) = n o m i n a l l o a d o r L E D c u r r e n t

V F = R e c t i f i e r d i o d e f o r w a r d v o l t a g e ( t y p i c a l l y 0 . 3 V )



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O u t p u t C a p a c i t o r S e l e c t i o n a n d L i n e R e g u l a t i o n

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A P P L I C A T I O N I N F O R M A T I O N ( c o n t i n u e d )

T h e s m a l l e r t h e i n d u c t o r v a l u e , t h e h i g h e r t h e s w i t c h i n g f r e q u e n c y o f t h e c o n v e r t e r b u t t h e l o w e r t h e e f f i c i e n c y .

T h e s e l e c t e d i n d u c t o r m u s t h a v e a s a t u r a t i o n c u r r e n t t h a t m e e t s t h e m a x i m u m p e a k c u r r e n t o f t h e c o n v e r t e r a s c a l c u l a t e d i n t h e p e a k c u r r e n t c o n t r o l s e c t i o n . U s e t h e m a x i m u m v a l u e f o r I ( L I M ) ( 6 0 0 m A ) f o r t h i s c a l c u l a t i o n .

A n o t h e r i m p o r t a n t i n d u c t o r p a r a m e t e r i s t h e D C r e s i s t a n c e . T h e l o w e r t h e D C r e s i s t a n c e t h e h i g h e r t h e

e f f i c i e n c y o f t h e c o n v e r t e r . S e e T a b l e 1 a n d F i g u r e 2 2 t o F i g u r e 2 7 f o r i n d u c t o r s e l e c t i o n .

T a b l e 1 . P o s s i b l e I n d u c t o r

I n d u c t o r V a l u e C o m p o n e n t S u p p l i e r S i z e

1 0 H m u R a t a L Q H 4 3 C N 1 0 0 K 0 1 4 , 5 m m 3 , 2 m m 2 . 6 m m

4 . 7 H m u R a t a L Q H 3 2 C N 4 R 7 M 1 1 3 , 2 m m 2 , 5 m m 2 , 0 m m

1 0 H C o i l c r a f t D O 1 6 0 5 T - 1 0 3 M X 5 , 5 m m 4 , 1 m m 1 , 8 m m

4 . 7 H S u m i d a C D R H 3 D 1 6 - 4 R 7 3 , 8 m m 3 , 8 m m 1 , 8 m m

3 . 3 H S u m i d a C M D 4 D 1 1 - 3 R 3 3 , 5 m m 5 , 3 m m 1 , 2 m m



4 . 7 H C o i l t r o n i c s S D 1 2 - 4 R 7 5 , 2 m m 5 , 2 m m 1 , 2 m m

3 . 3 H C o i l c r a f t L P O 1 7 0 4 - 3 3 2 M 6 , 6 m m 5 , 5 m m 1 , 0 m m

4 . 7 H C o i l c r a f t L P O 1 7 0 4 - 4 7 2 M 6 , 6 m m 5 , 5 m m 1 , 0 m m

F o r b e t t e r o u t p u t v o l t a g e f i l t e r i n g , a l o w E S R o u t p u t c a p a c i t o r i s r e c o m m e n d e d . C e r a m i c c a p a c i t o r s h a v e a l o w E S R v a l u e , b u t d e p e n d i n g o n t h e a p p l i c a t i o n , t a n t a l u m c a p a c i t o r s c a n b e u s e d .

T h e s e l e c t i o n o f t h e o u t p u t c a p a c i t o r v a l u e d i r e c t l y i n f l u e n c e s t h e o u t p u t v o l t a g e r i p p l e o f t h e c o n v e r t e r w h i c h a l s o i n f l u e n c e s l i n e r e g u l a t i o n . T h e l a r g e r t h e o u t p u t v o l t a g e r i p p l e , t h e l a r g e r t h e l i n e r e g u l a t i o n , w h i c h m e a n s t h a t t h e L E D c u r r e n t c h a n g e s i f t h e i n p u t v o l t a g e c h a n g e s . I f a c e r t a i n c h a n g e i n L E D c u r r e n t g i v e s a n o t i c e a b l e c h a n g e i n L E D b r i g h t n e s s , d e p e n d s o n t h e L E D m a n u f a c t u r e r a n d o n t h e a p p l i c a t i o n . A p p l i c a t i o n s r e q u i r i n g g o o d l i n e r e g u l a t i o n 1 % / V ( t y p ) m u s t u s e o u t p u t c a p a c i t o r v a l u e s 1 F .

S e e T a b l e 2 a n d F i g u r e 2 2 t o F i g u r e 2 7 f o r t h e s e l e c t i o n o f t h e o u t p u t c a p a c i t o r . A s s u m i n g t h e c o n v e r t e r d o e s n o t s h o w d o u b l e p u l s e s o r p u l s e b u r s t s o n t h e s w i t c h n o d e ( S W ) , t h e o u t p u t v o l t a g e r i p p l e i s c a l c u l a t e d a s ( s e e F i g u r e 1 3 , F i g u r e 1 4 ) :

w i t h :

I ( L I M ) = m i n i m u m s w i t c h c u r r e n t l i m i t ( 4 0 0 m A t y p )


I ( L O A D ) = n o m i n a l l o a d c u r r e n t

fS = s w i t c h i n g f r e q u e n c y a t t h e n o m i n a l l o a d c u r r e n t a s c a l c u l a t e d b e f o r e .

V F = r e c t i f i e r d i o d e f o r w a r d v o l t a g e ( 0 . 3 V t y p )

C O = s e l e c t e d o u t p u t c a p a c i t o r

E S R = o u t p u t c a p a c i t o r E S R v a l u e



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I n p u t C a p a c i t o r S e l e c t i o n

D i o d e S e l e c t i o n

E f f i c i e n c y

VLED

ILED

VI I

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T P S 6 1 0 4 2


F o r g o o d i n p u t v o l t a g e f i l t e r i n g , l o w E S R c e r a m i c c a p a c i t o r s a r e r e c o m m e n d e d . A 4 . 7 F c e r a m i c i n p u t c a p a c i t o r i s s u f f i c i e n t f o r m o s t a p p l i c a t i o n s . F o r b e t t e r i n p u t v o l t a g e f i l t e r i n g t h e c a p a c i t o r v a l u e c a n b e i n c r e a s e d . R e f e r t o T a b l e 2 a n d F i g u r e 2 2 t o F i g u r e 2 7 f o r i n p u t c a p a c i t o r s e l e c t i o n .

T a b l e 2 . P o s s i b l e I n p u t a n d O u t p u t C a p a c i t o r s

C a p a c i t o r V o l t a g e r a t i n g C o m p o n e n t S u p p l i e r C o m m e n t s

4 . 7 F / X 5 R / 0 8 0 5 6 . 3 V T a y o Y u d e n J M K 2 1 2 B Y 4 7 5 M G C I

1 0 F / X 5 R / 0 8 0 5 6 . 3 V T a y o Y u d e n J M K 2 1 2 B J 1 0 6 M G C I

1 0 0 n F A n y C O

2 2 0 n F A n y C O

4 7 0 n F A n y C O

1 . 0 F / X 7 R / 1 2 0 6 2 5 V T a y o Y u d e n T M K 3 1 6 B J 1 0 5 K L C O

1 . 0 F / X 7 R / 1 2 0 6 3 5 V T a y o Y u d e n G M K 3 1 6 B J 1 0 5 K L C O

4 . 7 F / X 5 R / 1 2 1 0 2 5 V T a y o Y u d e n T M K 3 2 5 B J 4 7 5 M G C O

T o a c h i e v e h i g h e f f i c i e n c y , a S c h o t t k y d i o d e m u s t b e u s e d . T h e c u r r e n t r a t i n g o f t h e d i o d e m u s t m e e t t h e p e a k c u r r e n t r a t i n g o f t h e c o n v e r t e r a s i t i s c a l c u l a t e d i n t h e p e a k c u r r e n t c o n t r o l s e c t i o n . U s e t h e m a x i m u m v a l u e f o r I ( L i m ) f o r t h i s c a l c u l a t i o n . S e e T a b l e 3 a n d F i g u r e 2 2 t o F i g u r e 2 7 f o r t h e S c h o t t k y d i o d e s e l e c t i o n .

T a b l e 3 . P o s s i b l e D i o d e s

C o m p o n e n t S u p p l i e r R e v e r s e v o l t a g e

O N S e m i c o n d u c t o r M B R 0 5 3 0 3 0 V

O N S e m i c o n d u c t o r M B R 0 5 2 0 2 0 V

T o s h i b a C R S 0 2 3 0 V

Z e t e x Z H C S 4 0 0 4 0 V

T h e o v e r a l l e f f i c i e n c y o f t h e a p p l i c a t i o n d e p e n d s o n t h e s p e c i f i c a p p l i c a t i o n c o n d i t i o n s a n d m a i n l y o n t h e s e l e c t i o n o f t h e i n d u c t o r . A l o w e r i n d u c t o r v a l u e i n c r e a s e s t h e s w i t c h i n g f r e q u e n c y a n d s w i t c h i n g l o s s e s y i e l d i n g i n a l o w e r e f f i c i e n c y . A l o w e r i n d u c t o r d c r e s i s t a n c e h a s l o w e r c o p p e r l o s s e s , g i v i n g a h i g h e r e f f i c i e n c y . T h e r e f o r e , t h e e f f i c i e n c y c a n t y p i c a l l y v a r y 5 % d e p e n d i n g o n t h e s e l e c t e d i n d u c t o r . F i g u r e 2 a n d F i g u r e 3 c a nb e u s e d a s a g u i d e l i n e f o r t h e a p p l i c a t i o n e f f i c i e n c y . T h e s e c u r v e s s h o w t h e t y p i c a l e f f i c i e n c y p o w e r i n g f o u r L E D s u s i n g a 4 . 7 H i n d u c t o r w i t h j u s t 1 , 2 m m h e i g h t . T h e e f f i c i e n c y c u r v e i n F i g u r e 2 a n d F i g u r e 3 s h o w t h e e f f i c i e n c y d e l i v e r i n g t h e p o w e r t o t h e L E D s r a t h e r t h a n t h e o v e r a l l c o n v e r t e r e f f i c i e n c y a n d i s c a l c u l a t e d a s :



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S e t t i n g T h e L E D C u r r e n t

VIN

CTRL

SW

OVP

GND

Rs

FB

LED

RS

PWM

100 Hz to 50 kHz

ILED

VFB

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0.252 V

RS

R2

PWM

Signal

C

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Optional Filter for theuse of a PWM Signal

VADJ(Brightness Control)

VIN

CTRL

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Rs

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LED

RS

Enable: CTRL = High

Disable: CTRL = Low

R1

I1

Vs

T P S 6 1 0 4 2


T h e c o n v e r t e r r e g u l a t e s t h e L E D c u r r e n t b y r e g u l a t i n g t h e v o l t a g e a c r o s s t h e c u r r e n t s e n s e r e s i s t o r ( R S ) . T h e v o l t a g e a c r o s s t h e s e n s e r e s i s t o r i s r e g u l a t e d t o t h e i n t e r n a l r e f e r e n c e v o l t a g e o f V ( F B ) = 2 5 2 m V .

F i g u r e 1 7 . S e t t i n g t h e L E D C u r r e n t

T h e L E D c u r r e n t c a n b e c a l c u l a t e d :

T h e c u r r e n t p r o g r a m m i n g m e t h o d i s u s e d w h e n t h e b r i g h t n e s s o f t h e L E D s i s f i x e d o r c o n t r o l l e d b y a P W M s i g n a l a p p l i e d t o t h e C T R L p i n . W h e n u s i n g a P W M s i g n a l o n t h e C T R L p i n , t h e L E D b r i g h t n e s s i s o n l y d e p e n d e n t o n t h e P W M d u t y c y c l e , i n d e p e n d e n t o f t h e P W M f r e q u e n c y , o r a m p l i t u d e , w h i c h s i m p l i f i e s t h e s y s t e m .

A l t e r n a t i v e l y , a n a n a l o g v o l t a g e c a n b e u s e d a s w e l l t o c o n t r o l t h e L E D b r i g h t n e s s .

F i g u r e 1 8 . S e t t i n g t h e L E D C u r r e n t



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R2Vref V

adj(min)

I1

R1 Vref

IO(max)

R2 Vadj(min)

IO(min)

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Vadj(max)

IO(max)

Vref I

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adj(min) I

O(min) V

ref I

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ref 1R1

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VS

IO(max)

T P S 6 1 0 4 2


I n F i g u r e 1 8 t h e L E D c u r r e n t i s d e t e r m i n e d b y t h e v o l t a g e a p p l i e d t o R 2 ( V ( a d j ) ) a n d t h e s e l e c t i o n o f R 1 , R 2 a n d t h e s e n s e r e s i s t o r ( R S ) . I n t h i s c o n f i g u r a t i o n , t h e L E D c u r r e n t i s l i n e a r c o n t r o l l e d i n s t e a d o f p u l s e d a s i n t h e c o n f i g u r a t i o n b e f o r e . T o s e l e c t t h e r e s i s t o r v a l u e s f o l l o w i n g s t e p s a r e r e q u i r e d .

1 . S e l e c t t h e v o l t a g e V ( a d j m a x ) t o t u r n t h e L E D s o f f . V( a d j m a x ) ( e . g . 3 . 3 V )

2 . S e l e c t t h e v o l t a g e V ( a d j m i n ) t o t u r n t h e L E D s f u l l y o n . V( a d j m i n ) ( e . g . 0 . 0 V )

3 . S e l e c t t h e m a x i m u m a n d m i n i m u m L E D c u r r e n t I O ( m a x ) a n d I O ( m i n ) . ( e . g . I O ( m a x ) = 2 0 m A , I O ( m i n ) = 0 m A )

4 . C a l c u l a t e R 2 t o a c h i e v e a f e e d b a c k c u r r e n t i n t h e r a n g e o f I 1 = 3 A t o 1 0 A a s t h e L E D s a r e f u l l y t u r n e d o n :

5 . C a l c u l a t i o n o f R 1

6 . C a l c u l a t i o n o f t h e s e n s e v o l t a g e ( V S ) a t m a x i m u m L E D c u r r e n t

7 . C a l c u l a t i o n o f t h e r e q u i r e d s e n s e r e s i s t o r ( R S )



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P W M C o n t r o l W i t h S e p a r a t e E n a b l e

Enable (EN)

VIN

CTRL

SW

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GND

FB

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PWM Brightness Control

100 Hz to 50 kHz

Enable (EN)

PWM Brightness Control100 Hz to 50 kHz

VIN

CTRL

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LED

FB

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L a y o u t C o n s i d e r a t i o n s

T h e r m a l C o n s i d e r a t i o n s

T P S 6 1 0 4 2


T h e c o n t r o l p i n ( C T R L ) c o m b i n e s t h e e n a b l e f u n c t i o n a s w e l l a s t h e P W M b r i g h t n e s s c o n t r o l f u n c t i o n i n o n e p i n . F o r s o m e s y s t e m s a n i n d e p e n d e n t e n a b l e f u n c t i o n i s r e q u i r e d . O n e w a y t o i m p l e m e n t t h i s i s t o u s e t h e b r i g h t n e s s c o n t r o l c o n f i g u r a t i o n a s s h o w n i n t h e p r e v i o u s s e c t i o n F i g u r e 1 8 .

O t h e r p o s s i b l e s o l u t i o n s a r e s h o w n i n F i g u r e 1 9 , F i g u r e 2 0 , F i g u r e 2 1 .

F i g u r e 1 9 . S e p a r a t e E n a b l e a n d P W M C o n t r o l U s i n g a S c h o t t k y D i o d e

F i g u r e 2 0 . S e p a r a t e E n a b l e a n d P W M C o n t r o l U s i n g a T r a n s i s t o r

F i g u r e 2 1 . S e p a r a t e E n a b l e a n d P W M C o n t r o l U s i n g a n A N D G a t e

I n a l l s w i t c h i n g p o w e r s u p p l i e s t h e l a y o u t i s a n i m p o r t a n t s t e p i n t h e d e s i g n , e s p e c i a l l y a t h i g h p e a k c u r r e n t s a n d s w i t c h i n g f r e q u e n c i e s . I f t h e l a y o u t i s n o t c a r e f u l l y d o n e , t h e r e g u l a t o r m i g h t s h o w n o i s e p r o b l e m s a n d d u t y c y c l e j i t t e r .

T h e i n p u t c a p a c i t o r s h o u l d b e p l a c e d a s c l o s e a s p o s s i b l e t o t h e i n p u t p i n f o r g o o d i n p u t v o l t a g e f i l t e r i n g . T h e i n d u c t o r a n d d i o d e m u s t b e p l a c e d a s c l o s e a s p o s s i b l e t o t h e s w i t c h p i n t o m i n i m i z e n o i s e c o u p l i n g i n t o o t h e r c i r c u i t s . S i n c e t h e f e e d b a c k p i n a n d n e t w o r k i s a h i g h i m p e d a n c e c i r c u i t , t h e f e e d b a c k n e t w o r k s h o u l d b e r o u t e d a w a y f r o m t h e i n d u c t o r .

T h e T P S 6 1 0 4 2 c o m e s i n a t h e r m a l l y e n h a n c e d Q F N p a c k a g e . T h e p a c k a g e i n c l u d e s a t h e r m a l p a d i m p r o v i n g t h e t h e r m a l c a p a b i l i t i e s o f t h e p a c k a g e . S e e t h e Q F N / S O N P C B A t t a c h m e n t a p p l i c a t i o n n o t e ( S L U A 2 7 1 ) .

T h e t h e r m a l r e s i s t a n c e j u n c t i o n t o a m b i e n t R J A o f t h e Q F N p a c k a g e g r e a t l y d e p e n d s o n t h e P C B l a y o u t . U s i n g t h e r m a l v i a s a n d w i d e P C B t r a c e s i m p r o v e s t h e t h e r m a l r e s i s t a n c e R J A . U n d e r n o r m a l o p e r a t i o n c o n d i t i o n s n o P C B v i a s a r e r e q u i r e d f o r t h e t h e r m a l p a d . H o w e v e r , t h e t h e r m a l p a d m u s t b e s o l d e r e d t o t h e P C B .



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www.ti.com

L14.7 H

Coilcraft LPO1704472

VIN

1.8 V to 6 V

C(IN)4.7 F

CO1 F

Enable/PWM Brightness

Control 100 HZ to 50 kHz

VIN

CTRL

SW

OVP

LED

D1ZHCS400

FB

GND

RS13

RS

C(IN)4.7 F

Enable/PWM Brightness


VIN

1.8 V to 6 V

RS13

VIN

CTRL

SW

OVP

LED

D1ZHCS400

FB

GND

L14.7 H

SUMIDA CMD4D11

CO4.7 F

RS

T P S 6 1 0 4 2


F i g u r e 2 2 . T P S 6 1 0 4 2 W i t h 1 , 0 m m T o t a l S y s t e m H e i g h t . E f f i c i e n c y = 8 2 . 7 % @ V I = 3 . 0 V / 1 9 m A

F i g u r e 2 3 . T P S 6 1 0 4 2 W i t h L o w L E D R i p p l e C u r r e n t a n d H i g h e r A c c u r a c y U s i n g a 4 . 7 F O u t p u t C a p a c i t o r



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VIN

CTRL

SW

OVP

LED

FB

GND

VIN

2.7 V to 6 V

C(IN)4.7 F

L1Sumida CDRH3D166R8

6.8 H

CO1 F

RS13Enable/PWM Brightness


RS

D1Zetex ZHCS400

VIN

CTRL

SW

OVP

LED

FB

GND

Rs

R1 R2

VIN

2.7 V to 6 V

CIN4.7 F

L110.0H

Coilcraft DO1605T103MX

CO100 nF

RS6.5 Enable/PWM Brightness


D1Zetex ZHCS400

30 30

T P S 6 1 0 4 2


F i g u r e 2 4 . T P S 6 1 0 4 2 P o w e r i n g 6 L E D s , E f f i c i e n c y = 8 4 % @ V I = 3 . 6 V / 1 9 m A

F i g u r e 2 5 . T P S 6 1 0 4 2 P o w e r i n g 8 L E D s , E f f i c i e n c y = 8 1 % @ V I = 3 . 6 V / 1 8 . 6 m A



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L14.7 H

VCC= 1.8 V to 6 V

C(IN)4.7 F

CO100 nF

Analog Brightness Control3.3 V LED Off

0 V ILED = 20 mA

RS13

VIN

CTRL

SW

OVP

LED

D1ZHCS400

FB

GND

R110 k

R2120 k

RS

L14.7 H

CIN4.7 F

CO100 nF

3.3 V PWM Signal

0 % LEDs on

100 % LEDs OffC

R

VIN

CTRL

SW

OVP

LED

D1ZHCS400

FB

GND

VCC= 1.8 V to 6 V

R110 k

R2120 k

RS13

RS

T P S 6 1 0 4 2


F i g u r e 2 6 . A d j u s t a b l e B r i g h t n e s s C o n t r o l U s i n g a n A n a l o g V o l t a g e

F i g u r e 2 7 . A l t e r n a t i v e A d j u s t a b l e B r i g h t n e s s C o n t r o l U s i n g P W M S i g n a l



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PACKAGING INFORMATION

Orderable Device Status (1) PackageType

PackageDrawing

Pins PackageQty

Eco Plan (2) Lead/Ball Finish MSL Peak Temp(3)

TPS61042DRBR ACTIVE SON DRB 8 3000 Green (RoHS &

no Sb/Br)

CU NIPDAU Level-2-260C-1 YEAR

TPS61042DRBRG4 ACTIVE SON DRB 8 3000 Green (RoHS &no Sb/Br)


TPS61042DRBT ACTIVE SON DRB 8 250 Green (RoHS &no Sb/Br)


TPS61042DRBTG4 ACTIVE SON DRB 8 250 Green (RoHS &no Sb/Br)


(1) The marketing status values are defined as follows:ACTIVE:Product device recommended for new designs.LIFEBUY:TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.NRND:Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part ina new design.PREVIEW:Device has been announced but is not in production. Samples may or may not be available.OBSOLETE:TI has discontinued the production of the device.

(2)Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check

http://www.ti.com/productcontentfor the latest availability information and additional product content details.TBD:The Pb-Free/Green conversion plan has not been defined.Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirementsfor all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be solderedat high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die andpackage, or 2) lead-based die adhesive used between the die and leadframe. The component is otherwise considered Pb-Free (RoHScompatible) as defined above.Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flameretardants (Br or Sb do not exceed 0.1% by weight in homogeneous material)

(3)MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder

temperature.

Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it isprovided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to theaccuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and continues to takereasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis onincoming materials and chemicals. TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limitedinformation may not be available for release.

In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TIto Customer on an annual basis.

PACKAGE OPTION ADDENDUM

www.ti.com 5-Mar-2007

Addendum-Page 1
http://www.ti.com/productcontenthttp://www.ti.com/productcontent


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TAPE AND REEL INFORMATION

*All dimensions are nominal

Device PackageType

PackageDrawing

Pins SPQ ReelDiameter

(mm)

ReelWidth

W1 (mm)

A0 (mm) B0 (mm) K0 (mm) P1(mm)

W(mm) Q

TPS61042DRBR SON DRB 8 3000 330.0 12.4 3.3 3.3 1.1 8.0 12.0

TPS61042DRBT SON DRB 8 250 180.0 12.4 3.3 3.3 1.1 8.0 12.0

PACKAGE MATERIALS INFORMATION


Pack Materials-Page 1


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*All dimensions are nominal

Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm)

TPS61042DRBR SON DRB 8 3000 346.0 346.0 29.0

TPS61042DRBT SON DRB 8 250 190.5 212.7 31.8

PACKAGE MATERIALS INFORMATION


Pack Materials-Page 2


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IMPORTANT NOTICE

Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications, enhancements, improvements,and other changes to its products and services at any time and to discontinue any product or service without notice. Customers shouldobtain the latest relevant information before placing orders and should verify that such information is current and complete. All products aresold subject to TIs terms and conditions of sale supplied at the time of order acknowledgment.

TI warrants performance of its hardware products to the specifications applicable at the time of sale in accordance with TIs standardwarranty. Testing and other quality control techniques are used to the extent TI deems necessary to support this warranty. Except where

mandated by government requirements, testing of all parameters of each product is not necessarily performed.

TI assumes no liability for applications assistance or customer product design. Customers are responsible for their products andapplications using TI components. To minimize the risks associated with customer products and applications, customers should provideadequate design and operating safeguards.

TI does not warrant or represent that any license, either express or implied, is granted under any TI patent right, copyright, mask work right,or other TI intellectual property right relating to any combination, machine, or process in which

Constant Current Led Driver

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