It is up to the designer to suggest provision of 4-wires on specific parts by consideration of board topology and functionality.Įvery digital/hybrid device should have provisions to be tri-stated. One approach that has been used in the industry is to mount one sample of low value components out of circuit on the board to verify that the correct value were loaded in the pick and place machine during assembly. If power up testing is desired, then the loading effect of the extra probes that are required for kelvin measurement may actually interfere with the functionality of the board specially on in-line resistors for high speed digital buses, low value components used in switching power supplies and sensitive analog circuits. Two separate test points must be provided on each side of the parts that require kelvin measurement. Kelvin measurement is utilized for high precision measurement of low value components (Resistors less then 100 ohms, Inductors less than 100mh, Capacitors less than 100nf). Provision must be included in the circuit for the tester to separately control all clock signals.įree-running clocks may cause test instability due to inability to squelch transients. use pull down or pull up resistor on all oscillators enable pins in order to disable them during ICT process. The control lines of oscillators should not be hard-wired directly to the voltage rail, ground, their own or other device's outputs.
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