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ADA4932 /PD pin

Update to a problem I found with an ADA4932-1 concerning the PD pin.

I have two circuits using this device, one is a balanced MFB active filter, the other a 2X analog line driver.

The MFB active filter uses a single 5V supply, the bus driver uses a symmetrical +-4.25V supply.

Both circuits use the /PD pins to conserve power.

The problem I see is that enabling the active filter at low temperatures, causes BOTH +ve and -ve outputs of the device to go to the positive rail (or at least within 1.2V of the rail). This condition can last 100s of milliseconds, depending on the temperature, so it seems like a leakage current issue combined with some capacitive charging/discharging.

The analog line driver does not suffer from this problem, either because the /PD function works as expected with the dual supply, or because there are no (large-ish) capacitors in the feedback network (as is the case for the active filter).

My question is, does the /PD function work properly with a single supply ?

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  • Hi Charly,

    I appreciate your response.

    We are using the devices with a single supply at +5V, maybe this affects

    the performance adversely ? VCMO is set at 2.5V by an external buffer.

    We begin to see issues at about 5C, and the time taken to begin

    operating correctly increases rapidly as the temperature is lowered

    further. At -15 we were seeing a 'recovery' time of the order of 30s or

    more.

    We have disabled the function in our system, we'll have to accept the

    increased power consumption.

    Perhaps you could answer another question for me, is this the lowest

    noise part in the AD range at this performance ?

    Thanks and regards

    Roger

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  • Hi Charly,

    I appreciate your response.

    We are using the devices with a single supply at +5V, maybe this affects

    the performance adversely ? VCMO is set at 2.5V by an external buffer.

    We begin to see issues at about 5C, and the time taken to begin

    operating correctly increases rapidly as the temperature is lowered

    further. At -15 we were seeing a 'recovery' time of the order of 30s or

    more.

    We have disabled the function in our system, we'll have to accept the

    increased power consumption.

    Perhaps you could answer another question for me, is this the lowest

    noise part in the AD range at this performance ?

    Thanks and regards

    Roger

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