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SN74CB3Q3257: Value of Internal Isolation Resistance

Part Number: SN74CB3Q3257

Hello Guys,

Good day.

Our customer is using four SN74CB3Q3257PWG4 in their design. Pin 10 of the parts have been lifted and not connected to the PCB pad.  He then measure the PCB pad to VCC and it is open.  When he measure the lifted pin 10 to VCC, he got 324k. Is this normal? He is expecting resistance in Megaohms.

They are connecting measurement points through these switches to DMM inputs.  A pull up at the least alters the measurement.  At worst, is connecting VCC to o their measurement point through an effective resistance of 324k.

He noticed this problem because he is tasked with proving no pin has an unexpected voltage. The switch pins are at about 2.5V, which is because he have a resistor to ground across the DMM probes.

Thanks in advance!

Art