tekHPoynt

by: Allan B. Dizon
The supply current (IDD) tests verify that the DUT supply current is not excessive. Although it is usually not specified, it is sometimes good practice to check for a minimum supply current. There are two methods for testing the device supply current. The first method is called static testing, because the device is not active. The second method is called dynamic testing, because the device is active while the current is being measured. Because the instruments for measuring DC vakues are slow in comparison to typical device execution speeds, dynamic testing usually makes use of a functional test loop. The device runs the same sequence repeatedly until the DC measurement is complete.


The IDD current can be measured once the device is in the specified condition. It is usually good practice to plan for settling time delay after the conditions are programmed and before making the measurements. There are some factors that may prevent the device from reaching the specified condition immediately, particularly the loadboard bypass capacitors and the settling time of the ATE system instruments.


As a suggestion, here's the general test sequence for a DUT:

• Force all input pins to 0 volts
• Force all output pins to 0 mA
• Force VDD to +12.0 volts
• Force VEE to - 12.0 volts
• Wait for the ATE instruments and DUT to settle
• Measure IDD current and compare with limits
• Measure IEE current and compare with limits