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PhilipsSemiconductors

AN171NE558 applications

1988 Dec

INTEGRATED CIRCUITS


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Philips Semiconductors Application note


2December 1988

INTRODUCTIONThe 558 is a monolithic Quad Timer designed to be used in the

timing range from a few microseconds to a few hours. Four entirely

independent timing functions can be achieved using a timing resistor

and capacitor for each section. Two sections of the quad may beinterconnected for astable operation. All four sections may be used

together, in tandem, for sequential timing applications up to several

hours. No coupling capacitors are required when connecting the

output of one timer section to the input of the next.

FEATURES

100mA output current per section

Edge-triggered (no coupling capacitor)

Output independent of trigger conditions

Wide supply voltage range 4.5V to 16V

Timer intervals from microseconds to hours

Time period equals RC

CIRCUIT OPERATIONSIn the one-shot mode of operation, it is necessary to supply a

minimum of two external components (the resistor and capacitor) for

timing. The time period is equal to the product of R and C. An output

load must be present to complete the circuit due to the output

structure of the 558.

For astable operation, it is desirable to cross-couple two devices

from the 558 Quad. The outputs are direct-coupled to the opposite

trigger input. The duty cycle can be set by the ratio of R1C1 to R2C2,

from close to zero to almost 100%. An astable circuit using one

timer is shown in Figure 5b.

OUTPUT STRUCTURE 558The 558 structure is open-collector which requires a pull-up resistor

to VCC and is capable of sinking 100mA per unit, but not to exceed

the power dissipation and junction temperature rating of the die and

package. The output is normally low and is switched high when

triggered.

RESETA reset function has been made available to reset all sections

simultaneously to an output low state. During reset the trigger is

disabled. After reset is finished, the trigger voltage must be taken

high and then low to implement triggering.

The reset voltage must be brought below 0.8V to insure reset.

THE CONTROL VOLTAGEThe control voltage is also made available on the 558 timer. This

allows the threshold

VCC

R1

C1

C2

C3

C4

2

7

10

15

R4 R3VCC

RESET

S1

5 133

1

68

119

14

16124

TR1RL1

S2

LOADSWITCH

(558)

(559)

R2

RL3

TR4RL4

TR2RL2

TR3

SL00990

Figure 1. 558 Test Circuit

voltage to be modulated, therefore controlling the output pulse width

and duty cycle with an external control voltage. The range of this

control voltage is from about 0.5V to VCC minus 1V. This will give a

cycle time variation of about 50:1. In a sequential timer with

voltage-controlled cycle time, the timing periods remain proportional

over the adjustment range.

TEST BOARD FOR 558The circuit layout can be used to test and characterize the 558 timer.

S2 is used to connect the loads to either VCC or ground. The main

precaution, in layout of the 558 circuit, is the path of the discharge

current from the timing capacitor to ground (Pin 12). The path must

be direct to Pin 12 and not on the ground bus. This is to prevent

voltage spikes on the ground bus return due to current switching

transient. It is also wise to use good power supply bypassing when

large currents are being switched.


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December 1988 3

a. Test Board Layout

b. Foil Side

V + 0R1 R4

V + 0R2 R3

2.2F

INPUTS

OUTPUTS

1 2 3

1 2 3

C1

C2

RL2

RL3

4

4

C3

C4

RESET

SI GND

LOAD

GND(559)

V +

V +(558)

SL00991

Figure 2.

VCC

TRIGGER

R

C

RL

T

TR 0

R

C T

TR 0

R

C T

TR 0

R

C

OUTPUT

T

TR 0

RL RL RL

TRIGGER

OUTPUT

T 4(RC) 2 HRS

SL00992

Figure 3. 558 Two-Hour Timer


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December 1988 4

CV CV CV CV

NOTE:

t1, t2, t3, t4 remain proportional over entire adj. range.

R1 C1

T

TR 0

OUTPUT

VCC

TRIGGER

VCC

OUTPUT 1

R1 C2

T

TR 0

OUTPUT 2

R1 C3

T

TR 0

OUTPUT 3

R1 C4

T

TR 0 OUTPUT 4

RL RL RL RL

TRIGGER

OUTPUT 1

OUTPUT 2

OUTPUT 3

OUTPUT 4

ADJ UP 50: 1 RANGE

SL00993

Figure 4. 558 Sequential Timer With Voltage-Controlled Cycle Time (50:1 Range)

a. Monostable Operation (One-Shot) b. 558 Astable Operation (Oscillator)

c. 558 Variable Frequency Oscillator with Fixed Duty Cycle

NOTE:

T = RC

VCC

R1

C1

T

TR0

OUTPUT

CV

RLRL R2

C2

TTR

0CV

INCREASEFREQUENCY

R

C

TTR0

VCC

TRIGGER

OUTPUT

VCC

R1

C1

TTR0

OUTPUT

RLRL R2

C2

TTR0

SL00994

Figure 5.

TOUTPUT

TRIGGER

OUTPUT 1

OUTPUT 2

OUTPUT 3

OUTPUT 4

TDELAY 3(R.C.)

TOUTPUT )R.C.)

TDELA

Y

VCC

TRIGGER

R1

C1

RL

T

TR 0

R1

C1

T

TR 0

R1

C1

T

TR 0

R1

C2

OUTPUT4

OUTPUT1 OUTPUT2 OUTPUT3

NOTUSED

T

TR 0

RL RL RL

SL00995

Figure 6. 558 Long Time Delay


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December 1988 5

T=RC

b. Expected Waveforms

a. Ring Counter

TRIG 01

TIME

13

3

5

2

R1

VCC

START

RESET

C1

RL

1

10K

TRIG 02

TIME

13

7

R1

C1

RL

8TRIG 03

TIME

13

10

R1

C1

RL

9TRIG 04

TIME

13

15

R1

C1

RL

166 11 14

12

VCC

START

RESET

01

02

03

04

SL00996

Figure 7.

R112.5K

TRIG 01

TIME

VCC = 15V

C1

C2

0.01FRL12.5K

0.1F

R2RESET

SL00997

Figure 8. NE558 400Hz Square Wave Oscillator

A single section of the quad time may be used as a non-precision

oscillator. The values given are for oscillation at about 400Hz. T1

R1C1 and T2 2.25 R2C2 for VCC of 15V. The frequency of

oscillation is subject to the changes in VCC.

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