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DAC8775: DVDD maximum output current

Zoey Wu
Expert 5855 points
Part Number: DAC8775
Other Parts Discussed in Thread: ISO7641FC, ISO7641FM

Tool/software:

hi team,

 when I read the datasheet 9.2, I  noticed that the DVDD is connected to the VCC2 of ISO7641. 

But the DVDD only connect one chip ISO7641,what about the other one chip's supply?  Can i use DVDD to supply the 2 chips ISO7641? Thanks!

  • 0
    TI__Expert 4680 points

    Hi Zoey,

    Based on the typical supply current of the ISO7641, the internal DVDD of the DAC8775 should be able to support two ISO7641.

    Thanks.
    Lucas

  • 0 in reply to Lucas Burnette
    TI__Expert 5855 points

    but as ISO7641's datasheet shows, 

    the maximum value of ICC2 are >5A except when EN1=EN2=0V. The power of DVDD can't support the two chips in other conditions. Thanks!

  • 0 in reply to Zoey Wu
    TI__Expert 5855 points

    Hi Lucas,

    Any update? thanks!

  • 0 in reply to Zoey Wu
    TI__Mastermind 42243 points

    Hi Zoey, 

    What supply current are you expecting from the two ISO7641? We shouldn't base off of the max from the datasheet, but instead use your expected current in the application. 

    Best,

    Katlynne Jones

  • 0 in reply to Katlynne Jones
    TI__Guru* 98025 points

    Zoey,


    I think short answer is that you can use the DVDD to power two ISO7641 devices. However, there are limitations to that.

    The ISO7641 current consumption depends on the data rate and how much capacitance the output is required to drive. If the capacitance is low, and the clock rate is 1Mbps, then I don't think this would be a problem. Looking at the ISO7641FC datasheet, the typical current for VCC2 at 5V is about 2.6mA. That would be about 5.2mA total to drive two devices. The maximum for this device is about 3.9mA.

    If they are using the ISO7641FM, then the current might be a little higher with about 4.6mA typical for each device. The maximum current is certainly higher at 6.7mA, and that might be too high.

    For the DAC8775, the datasheet says the max load current is 10mA. Again, this should be ok for the ISO7641FC device.


    Joseph Wu