In the MAX14827A design, customer pull up CS/PP pin, and use CQ as input, will it work? So far, they found CQ had been pulled to high after CS/PP pulled up. But after remove the pull up resistor, CQ becomes normal. Is this normal phenomenon?

Question

In the MAX14827A design, customer pull up CS/PP pin, and use CQ as input, will it work? So far, they found CQ had been pulled to high after CS/PP pulled up. But after remove the pull up resistor, CQ becomes normal.  Is this normal phenomenon?

Accepted Answer

This is the expected behavior. When the C/Q is set in PP mode (CS/PP = High), an internal pullup current (my measurements shown about 46uA) connect it to the supply. C/Q must be set in PNP mode or completely disabled (TXEN = low and CQ_DIS = 1 in the registers – can only be done with a serial interface) for the pullup current to be disabled.

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In the MAX14827A design, customer pull up CS/PP pin, and use CQ as input, will it work? So far, they found CQ had been pulled to high after CS/PP pulled up. But after remove the pull up resistor, CQ becomes normal. Is this normal phenomenon?