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TLV320DAC32: Internal LDO Issues

Arthur Thompson27
Expert 1840 points

Part Number: TLV320DAC32
Other Parts Discussed in Thread: CC8520,

I am trying to use the internal LDO in the TLV320DAC32 to power its core DVDD.  I'm noticing the DVDD rail takes a very long time (several hundred milliseconds) to come up and I'm wondering whether this is typical.  I'm using the DAC as a slave to a Purepath Wireless chipset (CC8520).  The delay in turning on DVDD seems to be causing the DAC to not ACK any I2C commands from the CC8520, and once DVDD is up the DAC responds on I2C correctly.

Can TI offer any guidance on using the LDO?  Do I have to wait several hundred msec for it to come up before writing, or is something going wrong in my design?

In below scope shots, yellow is DAC_RESETN, blue is AUD_I2C_SCL, green is AUD_I2C_SDA, and red is VDD at C653.

The first picture is a non acked I2C write while DVDD is low.  The second picture is acked while DVDD is high.  The last two pictures are wider timebase shots where we see DVDD turning on.

  • 0
    Expert 1840 points
    Solution here:
    The DAC32's internal DVDD does not turn on until AVDD and DRVDD are also turned on (I wish TI would have documented this behavior somehow). My internal LDO enables immediately after the AVDD and DRVDD are brought up. That rail was taking a long time to turn on because it's on a dedicated 3.0V LDO whose EN pin wasn't being purposely driven high (left configured as input by microcontroller). But the EN pin was eventually floating up to a high level, thus enabling the 3.0V LDO, and then after that the DAC32 performed correctly.

    Just wanted to clear that up for anybody who may be reading.

    Thanks,
    Arthur
  • 0
    TI__Guru** 114635 points
    Hi Arthur,

    I'll double check this on our EVM.
    All those cycles on Reset pin are part of the initialization? It looks like DVDD starts rising before the last cycle of Reset. Do you have captures of 3V0 rail? DRVDD is the one that powers the internal LDO.

    Best regards,
    -Ivan Salazar
    Applications Engineer - Low Power Audio & Actuators
  • 0 in reply to Arthur Thompson27
    TI__Guru** 114635 points
    Arthur,

    Sorry I didn't saw you post before replying.
    Thanks for coming back to clarify the situation.

    Best regards,
    -Ivan Salazar
    Applications Engineer - Low Power Audio & Actuators
  • 0 in reply to Ivan Salazar
    Expert 1840 points
    Ivan,

    Thanks for the additional info, I didn't realize DRVDD powers the internal LDO. I was thinking it was IOVDD, but on checking the datasheet I couldn't find it mentioned.

    The numerous resets I believe were the CC8520 automatically re-trying its initialization sequence when the DAC was unresponsive on I2C.

    All seems to be working now.
    Thanks,
    Arthur
  • 0 in reply to Arthur Thompson27
    TI__Guru** 114635 points

    Arthur,

    I apologize for the lack of information on the data sheet. The reference you can have of the LDO being powered by DRVDD is at the simplified block diagram, there is an arrow that indicates the input and output of LDO.

    Best regards,
    -Ivan Salazar
    Applications Engineer - Low Power Audio & Actuators