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BECAUSE TESTING MATTERS BECAUSE TESTING MATTERS In-Circuit Test Concepts Part 2 Analog In-circuit Michael J Smith

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Presentation on theme: "BECAUSE TESTING MATTERS BECAUSE TESTING MATTERS In-Circuit Test Concepts Part 2 Analog In-circuit Michael J Smith"— Presentation transcript:

1 BECAUSE TESTING MATTERS BECAUSE TESTING MATTERS In-Circuit Test Concepts Part 2 Analog In-circuit Michael J Smith

2 2 2 The 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 –Inhibits and Disables –Bus Testing –Boundary Scan –ISP and FLASH programming Part 4 - In-Circuit Program Development Process

3 3 3 Agenda: 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

4 4 4 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.

5 5 5 Defect Spectrum ICT finds defects! But it does not normally find potential defects in solder quality!

6 6 6 Analog 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 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

7 7 7 Initial Routines Capacitor Discharge –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. Capacitor Discharge –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.

8 8 8 Shorts 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

9 9 9 Alternative 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

10 10 Ohms 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:electrical circuitcurrentproportionalpotential differencevoltage dropvoltageresistance 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:electrical circuitcurrentproportionalpotential differencevoltage dropvoltageresistance I = V/R V=IR R = V/I

11 11 How is Ohms Law applied?

12 12 8-Wire Scanner Relay – Connected for a resister test

13 13 Real 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

14 14 Use of the Virtual Ground All the paths are connected together and a virtual earth is created

15 15 3- and 4-Terminal Guarded Measurement

16 16 4-Terminal Guarded Resistor Test

17 17 4-Terminal Guarded Resistor Test – Ex 2

18 18 Kelvin Resistor Test Relays and fixture resistance can effect low-value resistor measurements and therefore we use a Kelvin test ( <20 Ω).

19 19 6-Terminal Resistor Test

20 20 Electrical 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.Oliver Heaviside1886alternating 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.resistanceAC circuits voltagecurrentphases In general, impedance is a complex quantity ; the polar form conveniently captures both magnitude and phase characterstics,complexpolar form A term coined by Oliver Heaviside in July of 1886 to describe a measure of opposition to a sinusoidal alternating current.Oliver Heaviside1886alternating 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.resistanceAC circuits voltagecurrentphases In general, impedance is a complex quantity ; the polar form conveniently captures both magnitude and phase characterstics,complexpolar form

21 21 4-Wire Guarded Capacitor Test

22 22 4-Wire Guarded Inductor Test

23 23 Diode 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

24 24 Zener Diode Test Looks for the switch voltage.

25 25 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. GAIN = (IE2-IE1) - (IB2-IB1)/(IB2-IB1)

26 26 Other Tests Transformers –AC gains Relay –Switch Test Etc. Transformers –AC gains Relay –Switch Test Etc.

27 BECAUSE TESTING MATTERS BECAUSE TESTING MATTERS Powered Analog Tests

28 28 Applying 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

29 29 Op-Amp Test A number of preset test are normally available –This is a simple AC gains test A number of preset test are normally available –This is a simple AC gains test

30 30 A number of preset test are normally available –This is a simple switch to rail test A number of preset test are normally available –This is a simple switch to rail test Op-Amp Test

31 31 Powered Analog Frequency generator Plus generator Frequency generator Plus generator

32 32 Other 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.

33 BECAUSE TESTING MATTERS BECAUSE TESTING MATTERS Analog Digital Opens Testing

34 34 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

35 35 What is Analog Digital Opens? Capacitance Coupling Technique Software replaced by fixture hardware

36 36 Types 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 Component under Test PCB RCM Carrier Conductor Standard Nail Signal Detector KHz -0.6 Vdc V cc Gnd DUT V BIAS V 200 5

37 37 Active Buffer assembly Device- Under-Test AC Source Printed Circuit Board Opens Sensor IC Lead Filter Scanner AC Detector Probe Plate Gain Mux Board ICA Guard DUT Active Analog Opens

38 BECAUSE TESTING MATTERS BECAUSE TESTING MATTERS In-Circuit Test Concepts Part 2 Analog In-circuit Michael J Smith

39 39 The Sequels! Part 1 – In-Circuit Test Overview –http://atd-teradyne.01o.com/ajtk/servlet/JJ?H=13q7oj&R= /resource/type/web_recordings.html. 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 –http://atd-teradyne.01o.com/ajtk/servlet/JJ?H=13q7oj&R= /resource/type/web_recordings.html. 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


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