1. Lecture 3 Mixed Signal Testing
DC and Parametric Test

2. Continuity Testing Detect on-chip ESD devices
Validate Connection of Device to Tester
Eliminate DC Package Bridging Faults
mA current (over voltage)
Parallel testing to speed process
Current Limit
Test Accuracy

3. 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

4. Power Test II Testing over Operation Range
(Schmoo Plots): Voltage/Current/Freq
Earliest form of Binning
Memory devices
Processors

5. 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

6. DC Transfer Characteristics
Offset
Input or Output Referenced

7. Tester Loading Impedance
Input impedance of tester is not infinite
Possibility of substantial error

8. Output Offset Definition
Single Ended: relative to reference
Differential:
Common Mode (V1+V2)/2
Differential Mode (V1-V2)

9. 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

10. 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

11. Nulling Amplifier

12. Power Supply Rejection
Input held constant

13. Power Sensitivity Measurement

14. Common Mode Rejection Ratio
Measure Offset Voltage
Similar problem to Gain – need servo loop

15. 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

16. Digital DC Tests Iih/Iil Leakage Vih/Vil Thresholds Ioh/Iol Drives
Short Circuit Currents