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ADC081C021: What means "Floating" values?

Ivan Mahdík
Prodigy 30 points
Part Number: ADC081C021

Hello,

I have the ADC081C021 and in datasheet on 24 page is Table 2. Slave Addresses. I have question about the vlaue "Floating". It means the same as "MID"? My system will be use half level of power supply on this pins. Will be it work?

KR
Ivan

  • 0
    TI__Guru**** 173886 points

    Hi Ivan,

    For the ADC081C021, floating means 'no connection'.  Do not apply any voltage to the ADRx pin(s) at all if you want to use the address noted with the Floating entries.

  • 0 in reply to Tom Hendrick
    Prodigy 30 points

    Hi Tom,

    Thanks for your an answer. Yes, but on page 4 is illustrated internal connection of the address pins and on it are connected two pull-up resistor as "mid" level. So that means, that level on the unconnected pins wil be mid level, so it is the same as If I connect the "mid levels pull-up", resistors as external. What do you think about it?

    It is because my adaptive address selector architecture supporting threee-state logic High / Mid / Low. If I must be use "real" unconnection of the "floating" state, it will be very complicated for rebuild of my architecture. Beacuse them will be must support High / Mid / Float / Low ..

  • 0 in reply to Ivan Mahdík
    TI__Guru**** 173886 points

    Hi Ivan,

    The V+ shown in that figure is actually the VA pin and the 41.5K resistors are internal to the device.  You do not need to connect anything external to 'PIN' which would be the ADDRx pins.

  • 0 in reply to Tom Hendrick
    Prodigy 30 points

    My system does not supporting "anything external"... My question is will it be a problem if the pin has half the value of the power supply from my external "mid level". But I think it will be ok, because it will be the same as internal..

    If the external value of mid from system on picture above will be problem I would have to design the same field as I show in the picture above, but instead of one diode and a resistor, there would have to be 3 mosfets and that is already a lot of parts:

  • 0 in reply to Ivan Mahdík
    TI__Guru**** 173886 points

    You do not need to supply an external 'VMID'.  Leave the pins floating (open).

  • 0 in reply to Tom Hendrick
    Prodigy 30 points

    Okay I do not will use addressator with diodes, but I will use addressator with mosfets, because it supports High, Mid, Low and Floating states. Thanks