Presentation on theme: "In-Circuit Test Concepts Part 2 Analog In-circuit Michael J Smith"— Presentation transcript:
1 In-Circuit Test Concepts Part 2 Analog In-circuit Michael J Smith Michael.J.Smith@Teradyne.com
2 The Series Part 1 – In-Circuit Test Overview What and Why In-Circuit Test?The Defect SpectrumIn-circuit Test System ArchitecturePart 2 - In-Circuit Analog MeasurementShorts and Opens Testing2,3,4,6 Wire MeasurementR,C,L, Diode, Zener, Transistor MeasurementPowered Analog TestingAnalog Digital Opens TestingPart 3 - In-Circuit Digital TestingDigital VectorsBackdrivingInhibits and DisablesBus TestingBoundary ScanISP and FLASH programmingPart 4 - In-Circuit Program Development Process
3 Agenda: In-Circuit Analog Measurement IntroductionAnalog Test FlowStartup ProceduresShorts TestingResistor Measurement2,3,4,6 Wire MeasurementC,L, Diode, Zener, Transistor MeasurementPowered Analog TestingAnalog 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 defectsin solder quality!
6 Analog Test Program Flow Capacitor DischargeContact TestShorts TestAnalog Test – Un-poweredResistorCapacitorInductorDiodeTransistorsAnalog Digital OpensPower BoardPower Up TestsOp-Amps.Un Power Board
7 Initial Routines Capacitor Discharge Contact Test Checks for voltages on large capacitors and then removes potentialCan effect measurementNormal method is to discharge through a resistor to ground and measure the voltage,Contact TestLifts 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 nodesNumber of tests = Number of nodes -1
9 Alternative Shorts Tests Fast Shorts Test use a binary search methodNumber of tests = only log2 (N) testsFaster Shorts Testing by Anthony Suto, Teradyne Inc
10 I = V/R V=IR R = V/I Ohms Law 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/RI = V/RV=IRR = V/I
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,
25 Transistor TestTransistor 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 TestsTransformersAC gainsRelaySwitch TestEtc.
34 Why Analog Digital Opens Test? Increasing use of complex connectors and socketsLack of digital vectors
35 What is Analog Digital Opens? Capacitance Coupling TechniqueSoftware replaced by fixture hardware
36 Types of Analog Open Techniques Opens XpressPassive ProbeLow CostEasy of ManufactureFrameScan & FX ProbeActive ProbeHigh Signal IntegrityComponent under TestPCBRCMCarrierConductorStandard NailSignalDetector2 Vac@ 3.0 KHz-0.6 VdcVccGndDUTVBIAS+-2 V200 Ω5 Ω
37 Active Buffer assembly Active Analog OpensActive Buffer assemblyDevice-Under-TestACSourcePrintedCircuitBoardOpensSensorIC LeadFilterScannerDetectorProbe PlateGainMux BoardICAGuardDUT
38 In-Circuit Test Concepts Part 2 Analog In-circuit Michael J Smith Michael.J.Smith@Teradyne.com
39 The Sequels! Part 1 – In-Circuit Test Overview Part 3 - In-Circuit Digital TestingDigital VectorsBackdrivingInhibits and DisablesBus TestingBoundary ScanISP and FLASH ProgrammingPart 4 - In-Circuit Program Development Process