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Maximum Load on ISO7141CC pin

Dexter
Intellectual 450 points
Other Parts Discussed in Thread: DAC8760

Hello,

In my application i am using 2 DAC8760 and controlling it from a controller through ISO7141CC Isolator. SDI, SDO, SCLK(10Mhz) lines will be shared and separate Latch signal is provided for DAC selection.

My question is can ISO7141CC drive two DAC8760 ?? 

  • 0
    TI__Mastermind 46290 points
    Gaurav,

    I'm not intimately familiar with the ISO7141 but I'll at least add some information about the DAC8760 digital I/O and move this post to the forum for isolation products to get some inputs from the folks supporting ISO7141.

    The digital input current for the DAC8760 that the ISO7141 would need to drive is fairly low, specified as 1uA maximum. The digital output logic level thresholds expressed in the datasheet are specified with the condition of sourcing 200uA of current.

    Based on the typical characteristics curves in the ISO7141 datasheet it looks like the device is capable of sourcing enough current to drive several DAC8760s - it doesn't look like the output voltage changes significantly while sourcing several hundred microamperes. Similarly input current for most of the operating modes looks like it's only a few microamperes, well under the 200uA capabilities of the DAC8760.

    I'll move the post and let the ISO support team validate what I've mentioned here.
  • 0 in reply to Kevin Duke
    Intellectual 450 points

    Hello Kevin,

    Thanks for reply.

    Does SDO pin remain in High impedance state( no daisy chain, DAC are connected in parallel) when first 24 bit data goes into DAC through SDI pin. 

    What i am getting  from  the datasheet is...  SDO remain in High impedance until rising edge on latch signal is received.

  • 0 in reply to Kevin Duke
    TI__Genius 12025 points

    Hi Kevin, Gaurav,

    That's correct. The recommended maximum load for ISO7141 output pins is 4 mA, which is much higher than DAC8760 requirements (in uA). So this should not be a problem. You can also review Figures 4 and 5 in ISO7141 data sheet to see how Output voltage level varies with load. In this case, the impact is minimal.