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Original question:

AM26LV32: Leakage between boards

AM26LV32: Forcing a negative current on AM26LV32EIPWR input pins, A1-A4 and B1-B4 with device powered off

Barb Han
Prodigy 10 points
Part Number: AM26LV32

Tool/software:

When forcing negative current on AM26LV32EIPWR input pins, A1-A4 and B1-B4 with device powered off, the voltage measurement is about 3X greater than for the other pins (VCC and GND excluded). A1-A4 and B1-B4 measure almost -1.4 V with a forcing current of -50 uA. For the other pins, the forcing current is -100 uA.

A couple of questions 1) Are there ESD protection diodes on these inputs? If so, what type, and will it damage the device to force this much current with the device powered off? 2) What would be the recommended current for pin A1-A4 and B1-B4 (device unpowered)?

  • 0
    TI__Mastermind 48742 points

    Hi Barb,

    The differential inputs are shown in an equivalent circuit diagram found in figure 8.2:

    So there are diodes in the A/B path and the A/B pins have a different structure than other pins on this device (so voltage readings could be different)

    That being said we don't give a max current - it is not specified and we do not have data to back up any claim I could give you here. What we do specify is the max input voltage - i.e. the level where if you go past the max range damage is likely to occur - that is -4V to 8V for the A/B inputs on this device. Since the voltage is at -1.4V you are not in damage range so I don't think it is that much of a concern - but you are out of the recommended operational range which is going to be -0.3V to 5.5V single ended input on these pins - so behavior isn't strictly  guaranteed at that point that you are using. 

    Ultimately - this is a spec that needs to be qualified for your specific system - as long as the input voltage on A/B stays in the range of -4V to 8V with or without power applied to VCC we don't see a huge damage risk - but we didn't specify this current parameter as a specification for this device so we don't have data for your exact questions - all I can really say is that there are diodes and -1.4V is within our abs. max conditions so the current measurement doesn't worry me w.r.t. damage in system. 

    Best,

    Parker Dodson