07-05-2014, 02:16 PM
DC and Parametric Measurements
DC and Parametric.ppt (Size: 140 KB / Downloads: 21)
Continuity
Serial vs. Parallel Continuity Testing
Serial is one pin at a time
Test time intensive
Parallel can not see pin to pin shorts
Alternating odd and even pin parallel test
Analog parallel per-pin measurement is not available in some testers
Single current source and volt meter can be used one pin at a time
Digital per-pin measurement is available, but may introduce noise into sensitive analog circuit
Leakage Currents
Leakage Test Technique
Force DC voltage - measure small current
Typically measured twice
input voltage equal to positive supply
input voltage set to ground or negative supply
Input current high (IIH) and input current low (IIL)
Digital and analog inputs
Output leakage current (IOZ)
Measured same as IIH & IIL
output pin must be placed in a high impedance (HIZ) state using test modes
Power Supply Currents
Importance of Supply Current Tests
Fast method for determining catastrophic failure
Large current draw from power supplies
Tests are run early in test protocol to weed out defective chips without wasting valuable test time
Customer specific application characteristic
Battery operated instruments like a cellular phone require minimal current draw by electronics
DC References and Regulators
Voltage Regulators
High voltage input - regulated lower voltage output
Output voltage
simple voltmeter reading
Output voltage regulation
ability of regulator to maintain specific output under load
Dropout voltage
minimum input voltage before output drops below specified level
Input regulation
ability of regulator to maintain steady output with a range of input voltages
DC Gain Measurements
Closed Loop Gain
Single input
Change in output divided by the change in input
Use a voltmeter to measure output
input should be stable to within 1mV
may need testers high accuracy voltmeter to measure the values
Differential input
Change in differential output divided by change in differential input
DC offsets at the input are cancelled out
Use a differential voltmeter