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ADS1278 AVDD regulator heating issue

umamaheswar peta
Expert 1370 points
Other Parts Discussed in Thread: ADS1278, LM1117

Hi,

We are using ADS 1278 IC. When we are switch on the power after sometime that particular AVDD regulator was heated.
Any suggestion from your side.

Rgds,

Uma Mahesh

  • 0
    TI__Guru 66196 points
    Hi Uma,

    Thank you for your post.

    To start, I will need you to clarify what you are using as a regulator for AVDD. Does this supply power to only the ADS1278 AVDD pins? How much current is drawn from the regulator?

    Best Regards,
  • 0 in reply to Ryan Andrews
    Expert 1370 points

    Hi Andrews,

    We are using LM1117 regulator and this is used for regulator O/P only give to ADS1278 power 700mA, this is the max current.

    Please find attached schematics for your reference.

    Rgds,

    Uma Maheshuma.pdf

  • 0 in reply to umamaheswar peta
    TI__Guru 66196 points
    Hi Uma,

    The ADS1278 should not consume more than 176mA maximum. Do you have the analog and digital grounds tied together? You must ensure that the two grounds are never more than +/-300mV apart; otherwise, you risk damaging the device.

    Regards,
  • 0 in reply to Ryan Andrews
    Expert 1370 points

    Hello Andrew,

    We have short to both ground(Analog & Digital) in particular end.

    But we are facing the problem in reverse voltage. Remove the AVDD power supply and switch on the power that time measure the AVDD supply is come to +2.5V. how do solve it.

    Kindly let us know if any modifications required in the schematics which i posted in my earlier post.

    Rgds,

    Uma Mahesh

  • 0 in reply to umamaheswar peta
    TI__Guru 66196 points

    Hi Uma,

    Can you please clarify what you mean by "reverse voltage?" 

    Other questions/comments I have about your power circuit:

    1. Where do the +12V and +5V supplies come from?
    2. From the +12V, you produce AVDD_+5V. Is this the fixed-output version of the LM1117?
    3. From the +5V, you produce:
      1. DVDD_+1.8V
      2. VREF_+2.5V (analog ground should be used for VREFN)
      3. IOVDD_+3.3V

    I'm not a power expert, but the basic required connections seem ok for the ADS1278. I would suggest having someone from the TI Linear Power team to review your LM1117 application circuit.

    Best Regards,

  • 0 in reply to Ryan Andrews
    Expert 1370 points
    Hi Andrews,

    we are removing the AVDD regulator (not assembling). But that VREF regulator supply connect to ADS 1278. Now I switch on the power supply that same I measure the AVDD pin in the ADS1278 ic refer to gnd. Multi meter showing to 2.5V for the ADS1278 IC ( AVDD pin). How to do avoid the power?

    1. SMPS
    2. Fixed o/p
    3. SMPS +5V direct connect to all the regulator ( DVDD, VREF & IOVDD)

    Rgds,
    Uma Mahesh
  • 0 in reply to umamaheswar peta
    TI__Guru 66196 points
    Hi Uma,

    You may have a short-circuit between the VREF_+2.5V and AVDD_+5V. I would measure the impedance with a multimeter between these two nets while power is OFF.

    Hope this helps,