BECAUSE TESTING MATTERS BECAUSE TESTING MATTERS In-Circuit Test Concepts Part 2 Analog In-circuit...

BECAUSE TESTING MATTERSBECAUSE TESTING MATTERS

In-Circuit Test

Concepts

Part 2

AnalogIn-circuit

Michael J Smith

[email protected]

In-Circuit Test

Concepts

Part 2

AnalogIn-circuit

Michael J Smith

[email protected]

22

The SeriesThe Series

• Part 1 – In-Circuit Test Overview– What and Why In-Circuit Test?

– The Defect Spectrum

– In-circuit Test System Architecture

• Part 2 - In-Circuit Analog Measurement– Shorts and Opens Testing

– 2,3,4,6 Wire Measurement

– R,C,L, Diode, Zener, Transistor Measurement

– Powered Analog Testing

– Analog Digital Opens Testing

• Part 3 - In-Circuit Digital Testing– Digital Vectors

– Backdriving

– Inhibits and Disables

– Bus Testing

– Boundary Scan

– ISP and FLASH programming

• Part 4 - In-Circuit Program Development Process

• Part 1 – In-Circuit Test Overview– What and Why In-Circuit Test?

– The Defect Spectrum

– In-circuit Test System Architecture

• Part 2 - In-Circuit Analog Measurement– Shorts and Opens Testing

– 2,3,4,6 Wire Measurement

– R,C,L, Diode, Zener, Transistor Measurement

– Powered Analog Testing

– Analog Digital Opens Testing

• Part 3 - In-Circuit Digital Testing– Digital Vectors

– Backdriving


– Bus Testing

– Boundary Scan

– ISP and FLASH programming


33

Agenda: In-Circuit Analog MeasurementAgenda: In-Circuit Analog Measurement

• Introduction

• Analog Test Flow

• Startup Procedures

• Shorts Testing

• Resistor Measurement

• 2,3,4,6 Wire Measurement

• C,L, Diode, Zener, Transistor Measurement

• Powered Analog Testing

• Analog Digital Opens Testing

• Introduction

• Analog Test Flow

• Startup Procedures

• Shorts Testing

• Resistor Measurement

• 2,3,4,6 Wire Measurement

• C,L, Diode, Zener, Transistor Measurement

• Powered Analog Testing

• Analog Digital Opens Testing

44

What is In-Circuit Test?What is In-Circuit Test?

• Uses a “Bed of Nails” to access as many electrical nodes on the Unit Under Test (UUT) as possible.

• Voltage and current source(s) and measure(s) are used to test analog devices, one device at as time, using guarding techniques to negate the effects of other devices.

• A technique called backdriving, using voltage overdriving, is used to test digital devices in isolation with digital vectors by voltage forcing techniques.

• Uses a “Bed of Nails” to access as many electrical nodes on the Unit Under Test (UUT) as possible.

• Voltage and current source(s) and measure(s) are used to test analog devices, one device at as time, using guarding techniques to negate the effects of other devices.

• A technique called backdriving, using voltage overdriving, is used to test digital devices in isolation with digital vectors by voltage forcing techniques.

55

Defect SpectrumDefect Spectrum

ICT finds defects!

But it does not normally find potential defectsin solder quality!

66

Analog Test Program FlowAnalog Test Program Flow

• Capacitor Discharge

• Contact Test

• Shorts Test

• Analog Test – Un-powered– Resistor

– Capacitor

– Inductor

– Diode

– Transistors

• Analog Digital Opens

• Power Board

• Power Up Tests– Op-Amps.

• Un Power Board


• Contact Test

• Shorts Test

• Analog Test – Un-powered– Resistor

– Capacitor

– Inductor

– Diode

– Transistors

• Analog Digital Opens

• Power Board

• Power Up Tests– Op-Amps.

• Un Power Board

77

Initial RoutinesInitial Routines


– Checks for voltages on large capacitors and then removes potential Can effect measurement

Normal method is to discharge through a resistor to ground and measure the voltage,

• Contact Test

– Lifts the potential of the board ( VCC and GND ) and checks to see if all contacting nails reflect the raised potential.


– Checks for voltages on large capacitors and then removes potential Can effect measurement

Normal method is to discharge through a resistor to ground and measure the voltage,

• Contact Test

– Lifts the potential of the board ( VCC and GND ) and checks to see if all contacting nails reflect the raised potential.

88

Shorts TestsShorts Tests

• Shorts Test

– Check for shorts between all points

– Normal shorts test is to test one node against all other nodes

– Number of tests = Number of nodes -1

• Shorts Test

– Check for shorts between all points

– Normal shorts test is to test one node against all other nodes

– Number of tests = Number of nodes -1

99

Alternative Shorts TestsAlternative Shorts Tests

• Fast Shorts Test use a binary search method

– Number of tests = only log2 (N) tests

• Fast Shorts Test use a binary search method

– Number of tests = only log2 (N) tests

Faster Shorts Testing by Anthony Suto, Teradyne Inc

1010

Ohms LawOhms Law

• states that, in an electrical circuit, the current passing through a conductor between two points is proportional to the potential difference (i.e. voltage drop or voltage) across the two points, and inversely proportional to the resistance between them. In mathematical terms, this is written as:

I = V/R

• states that, in an electrical circuit, the current passing through a conductor between two points is proportional to the potential difference (i.e. voltage drop or voltage) across the two points, and inversely proportional to the resistance between them. In mathematical terms, this is written as:

I = V/R

I = V/RV=IRR = V/I

1111

How is Ohm’s Law applied?How is Ohm’s Law applied?

1212

8-Wire Scanner Relay – Connected for a resister test8-Wire Scanner Relay – Connected for a resister test

1313

Real Life CircuitsReal Life Circuits

• Only a few measurements are per 2-terminal

– Series, Pull-ups, Pull-downs and Terminators etc.

– Minimize Voltage!

• Most other circuits and networks of resistors

• Only a few measurements are per 2-terminal

– Series, Pull-ups, Pull-downs and Terminators etc.

– Minimize Voltage!

• Most other circuits and networks of resistors

1414

Use of the Virtual GroundUse of the Virtual Ground

• All the paths are connected together and a virtual earth is created

• All the paths are connected together and a virtual earth is created

1515

3- and 4-Terminal Guarded Measurement3- and 4-Terminal Guarded Measurement

1616

4-Terminal Guarded Resistor Test4-Terminal Guarded Resistor Test

1717

4-Terminal Guarded Resistor Test – Ex 24-Terminal Guarded Resistor Test – Ex 2

1818

Kelvin Resistor TestKelvin Resistor Test

• Relays and fixture resistance can effect low-value resistor measurements and therefore we use a “Kelvin” test ( <20 Ω).

• Relays and fixture resistance can effect low-value resistor measurements and therefore we use a “Kelvin” test ( <20 Ω).

1919

6-Terminal Resistor Test6-Terminal Resistor Test

DCSV

DCSV OUT(Source)

DCSV OUTS(Source Sense)

DCSV REFS(Source Low Sense)

DCSV REF(Source Low)

Ra

Rdut

Rb

DCMI

DCMI IN(Measure)

DCMI INS(Measure Sense)

DCMI GRDS(Guard Sense)

S M

AREF(Guard)

6388.0

CHA

CHE

CHB

CHF

67 42

2020

Electrical Impedance, or Simply ImpedanceElectrical Impedance, or Simply Impedance

• A term coined by Oliver Heaviside in July of 1886 to describe a measure of opposition to a sinusoidal alternating current.

• Electrical impedance extends the concept of resistance to AC circuits, describing not only the relative magnitudes of the voltage and current, but also the relative phases.

• In general, impedance is a complex quantity ; the polar form conveniently captures both magnitude and phase characterstics,

• A term coined by Oliver Heaviside in July of 1886 to describe a measure of opposition to a sinusoidal alternating current.

• Electrical impedance extends the concept of resistance to AC circuits, describing not only the relative magnitudes of the voltage and current, but also the relative phases.

• In general, impedance is a complex quantity ; the polar form conveniently captures both magnitude and phase characterstics,

2121

4-Wire Guarded Capacitor Test4-Wire Guarded Capacitor Test

2222

4-Wire Guarded Inductor Test4-Wire Guarded Inductor Test

2323

Diode TestDiode Test

• Looks for the characteristic knee voltage ( Typ 0.65V)

• Also use the dynamic resistance as a secondary test

• Looks for the characteristic knee voltage ( Typ 0.65V)

• Also use the dynamic resistance as a secondary test

R

VS

VM

IS

S M

REF

SLOPE = RF (DYNAMIC)

S

VFV

I

3777.0

2424

Zener Diode TestZener Diode Test

R

VS

VM

S MZZT

S

VZV

IZT

I

3778.0

• Looks for the switch voltage.• Looks for the switch voltage.

2525

Transistor Test Transistor Test

• Transistor NPN and PNP tests are normal gain measurements.

– Set the current source to a nominal predetermined value (IE1).

– Measure the current in the base circuit (IB1).

– Slightly increase the current source to a new known value (IE2).

– Measure the new current in the base circuit (IB2).

– Use the values in the following formula to calculate the gain.

• Transistor NPN and PNP tests are normal gain measurements.

– Set the current source to a nominal predetermined value (IE1).

– Measure the current in the base circuit (IB1).

– Slightly increase the current source to a new known value (IE2).

– Measure the new current in the base circuit (IB2).

– Use the values in the following formula to calculate the gain.

REF.

I MM

VM

I S

31832.0

GAIN = (IE2-IE1) - (IB2-IB1)/(IB2-IB1)

2626

Other TestsOther Tests

• Transformers

– AC gains

• Relay

– Switch Test

• Etc.

• Transformers

– AC gains

• Relay

– Switch Test

• Etc.


Powered Analog TestsPowered Analog Tests

2828

Applying PowerApplying Power

• Power needs to applied correctly ie emulate the system supply

– Right order, timing and slew rate

– Limited Current

– Verify Stable

– Verify Voltage Levels

• Power needs to applied correctly ie emulate the system supply

– Right order, timing and slew rate

– Limited Current

– Verify Stable

– Verify Voltage Levels

2929

Op-Amp TestOp-Amp Test

• A number of preset test are normally available

– This is a simple AC gains test


– This is a simple AC gains test

3030


– This is a simple switch to rail test


– This is a simple switch to rail test

Op-Amp TestOp-Amp Test

3131

Powered AnalogPowered Analog

• Frequency generator

• Plus generator

• Frequency generator

• Plus generator

3232

Other Analog TestsOther Analog Tests

• Custom Test – Needs language support

– V,I,

– Frequency

– V and I measured over time for complex waveform

• Hybrid Tests – Synchronized Analog and Digital

– D to A

– A to D

– Complex circuits.

• Custom Test – Needs language support

– V,I,

– Frequency

– V and I measured over time for complex waveform

• Hybrid Tests – Synchronized Analog and Digital

– D to A

– A to D

– Complex circuits.


Analog Digital Opens TestingAnalog Digital Opens Testing

3434

Why Analog Digital Opens Test? Why Analog Digital Opens Test?

• Increasing use of complex connectors and sockets

• Lack of digital vectors

• Increasing use of complex connectors and sockets

• Lack of digital vectors

3535

What is Analog Digital Opens?What is Analog Digital Opens?

• Capacitance Coupling Technique• Capacitance Coupling Technique

• Software replaced by fixture hardware

3636

Types of Analog Open TechniquesTypes of Analog Open Techniques

•Opens Xpress

–Passive Probe

–Low Cost

–Easy of Manufacture

•Opens Xpress

–Passive Probe

–Low Cost

–Easy of Manufacture

•FrameScan & FX Probe

–Active Probe

–High Signal Integrity

•FrameScan & FX Probe

–Active Probe

–High Signal Integrity

Component under Test

PCBRCM

Carrier

Conductor

Standard Nail

SignalDetector

2 Vac@ 3.0 KHz-0.6 Vdc

Vcc Gnd

DUTVBIAS

+

-2 V

200 Ω

5 Ω

3737

Active Buffer assembly

Device-Under-Test

AC Source

PrintedCircuit Board

Opens Sensor

IC Lead

FilterFilter

Scanner

ACDetector

Probe Plate

GainGain

Mux Board

ICA

Guard

DUT

Active Analog OpensActive Analog Opens


In-Circuit Test

Concepts

Part 2

AnalogIn-circuit

Michael J Smith

[email protected]

In-Circuit Test

Concepts

Part 2

AnalogIn-circuit

Michael J Smith

[email protected]

3939

The Sequels!The Sequels!

• Part 1 – In-Circuit Test Overview– http://atd-teradyne.01o.com/ajtk/servlet/JJ?H=13q7oj&R=665215672/resource/type/web_recordings.html.

• Part 3 - In-Circuit Digital Testing

– Digital Vectors

– Backdriving


– Bus Testing

– Boundary Scan

– ISP and FLASH Programming


• Part 1 – In-Circuit Test Overview– http://atd-teradyne.01o.com/ajtk/servlet/JJ?H=13q7oj&R=665215672/resource/type/web_recordings.html.

• Part 3 - In-Circuit Digital Testing

– Digital Vectors

– Backdriving


– Bus Testing

– Boundary Scan

– ISP and FLASH Programming


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