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Lecture 3 Mixed Signal Testing. DC and Parametric Test. Continuity Testing. Detect on-chip ESD devices Validate Connection of Device to Tester Eliminate DC Package Bridging Faults 0.1-1.0mA current (over voltage) Parallel testing to speed process Current Limit Test Accuracy.

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lecture 3 mixed signal testing

Lecture 3 Mixed Signal Testing

DC and Parametric Test

continuity testing
Continuity Testing
  • Detect on-chip ESD devices
  • Validate Connection of Device to Tester
  • Eliminate DC Package Bridging Faults
  • 0.1-1.0mA current (over voltage)
  • Parallel testing to speed process
    • Current Limit
    • Test Accuracy
power supply test iddq
Power Supply Test: Iddq
  • Many manufacturing defects result in abnormal power current
    • Metal Errors – shorted traces
    • Implant/Diffusion errors – shorted substrate
    • Faulty ESD Clamps
    • Open/Floating Wells
    • Open/Floating Digitial gate input
power test ii
Power Test II
  • Testing over Operation Range
  • (Schmoo Plots): Voltage/Current/Freq
  • Earliest form of Binning
    • Memory devices
    • Processors
impedance measurement
Impedance Measurement
  • Z=V/I (Usually Z=DV/DI)
    • Force V, measure I (High Impedance)
    • Force I, Measure V (Low Impedance)
  • Defined Testing Levels
    • Reduce possibility of DUT damage
    • Increase accuracy of measurement
dc transfer characteristics
DC Transfer Characteristics
  • Offset
    • Input or Output Referenced
tester loading impedance
Tester Loading Impedance
  • Input impedance of tester is not infinite
    • Possibility of substantial error
output offset definition
Output Offset Definition
  • Single Ended: relative to reference
  • Differential:
    • Common Mode (V1+V2)/2
    • Differential Mode (V1-V2)
input offset
Input Offset
  • Voltage (Current) needed to set output voltage (current) at reference level
  • In theory– can measure ouput offset and divide by gain
  • In practice– gain often too high – device output is pinned to rail
measuring gain
Measuring Gain
  • For practical Op-Amps, gain is high
    • Use Nulling amplifier and resistor divider
    • Null Amplifier acts as servo to drive ouput voltage to known reference
    • Resistor divider acts to lower input sensitivity
  • Need Loop Compensation
  • Want Divider ratio similar to expected Gain
  • Can get input offset as well by choosing null reference goal
power supply rejection
Power Supply Rejection
  • Input held constant
common mode rejection ratio
Common Mode Rejection Ratio
  • Measure Offset Voltage
  • Similar problem to Gain – need servo loop
voltage search
Voltage Search
  • Need to set input to fix complex output
  • Three ideas:
    • Step Search (Ramp)
      • Issue (Cost of test)
    • Binary Search (Faster)
      • Issue (Hysteresis of DUT or Tester)
    • Linear Search (Simplified form of Newton)
      • Needs Computerized Tester
digital dc tests
Digital DC Tests
  • Iih/Iil Leakage
  • Vih/Vil Thresholds
  • Ioh/Iol Drives
  • Short Circuit Currents