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In-Circuit Test Concepts Part 2 Analog In-circuit Michael J Smith Michael.J.Smith@Teradyne

In-Circuit Test Concepts Part 2 Analog In-circuit Michael J Smith Michael.J.Smith@Teradyne.com. 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

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In-Circuit Test Concepts Part 2 Analog In-circuit Michael J Smith Michael.J.Smith@Teradyne

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  1. In-Circuit Test ConceptsPart 2AnalogIn-circuitMichael J SmithMichael.J.Smith@Teradyne.com

  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

  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

  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.

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

  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

  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.

  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

  9. Alternative Shorts 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. 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: • I = V/R I = V/R V=IR R = V/I

  11. How is Ohm’s Law applied?

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

  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

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

  15. 3- and 4-Terminal Guarded Measurement

  16. 4-Terminal Guarded Resistor Test

  17. 4-Terminal Guarded Resistor Test – Ex 2

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

  19. 6-Terminal Resistor Test

  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. • 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,

  21. 4-Wire Guarded Capacitor Test

  22. 4-Wire Guarded Inductor Test

  23. Diode Test • Looks for the characteristic knee voltage ( Typ 0.65V) • Also use the dynamic resistance as a secondary test

  24. Zener Diode Test • Looks for the switch voltage.

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

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

  27. Powered Analog Tests

  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

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

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

  31. Powered Analog • Frequency generator • Plus generator

  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.

  33. Analog Digital Opens Testing

  34. Why Analog Digital Opens Test? • Increasing use of complex connectors and sockets • Lack of digital vectors

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

  36. Opens Xpress Passive Probe Low Cost Easy of Manufacture FrameScan & FX Probe Active Probe High Signal Integrity 5 Ω 2 Vac @ 3.0 KHz -0.6 Vdc 200 Ω DUT - Signal Detector 2 V VBIAS + Conductor Vcc Gnd Carrier RCM PCB Component under Test Standard Nail Types of Analog Open Techniques

  37. Gain Filter Opens Sensor Scanner MuxBoard Device- Under-Test ActiveBufferassembly ProbePlate DUT ICLead Printed Circuit Board Guard AC Source AC Detector ICA Active Analog Opens

  38. In-Circuit Test ConceptsPart 2AnalogIn-circuitMichael J SmithMichael.J.Smith@Teradyne.com

  39. 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 • Inhibits and Disables • Bus Testing • Boundary Scan • ISP and FLASH Programming • Part 4 - In-Circuit Program Development Process

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