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TLV9064: Higher current draw from the -V supply then from the +V supply

Jim Lumpkin
Prodigy 30 points
Part Number: TLV9064

Issue with high -V supply current.

 

The +2.5 V is pulling approx..150 mA for total of 50 packages (200 amplifiers) whereas the -2.5 V pulls 750 mA.  If averaged, that is 750 uA/Amplifier from +2.5 V and 3.75 mA/Amplifier from -2.5 V.  At first turn on, shutdown pins were floating, but now pins are tied to + 2.5 V and issue of high current still remains.

 

The actual part number that I am using is TLV9064IRTER.

 

I still need to very much get to the bottom of this problem of the operating current not matching closely the data sheet.

 

Please get back with me soon.

 

Thank you,

Jim

  • 0
    TI__Guru**** 165146 points

    Hello Jim,

    How are the op amp biased?

    If Kirchhoff's Current Law is used on the whole test board then there must at least one other current flowing other than just +2.5V and -2.5V supplies. 'Ground' current perhaps?

    If Kirchhoff's Current Law is used on an individual TLV9064 then there must be other current(s) flowing other than just V+ and V- pins. Could this be output pin current into a load? Could it be input current for pin(s) with voltage that is higher than V+ or lower than V-.

  • 0 in reply to Ron Michallick
    Prodigy 30 points
    Hello Ronald,
    Thank you for responding as soon as you have.
    And I believe I know what is happening and that is, that our layout person has tied the center thermal pad to GND and not V-.  With this being the case, what is the impedance in the package between the thermal pad and V-?  It can't tied together...it would be much higher current if it were.
    My reason for the question is that I will want to try and make some progress on the use of my board (the amps seem to function fine) and turn on, check some system performance, turn off and let cool and then turn on again...keeping the on times to a minimum.  Hopefully, making some other system performance checks while we spin another board.  The amp output signals will be small enough in amplitude to function inside the imbalance (will be setting a current limit on the -2.5 V) of the supplying rails.
    Please let me know your thoughts...
    Regards,
    Jim 
  • 0 in reply to Jim Lumpkin
    TI__Guru**** 165146 points

    Jim,

    I believe you have found the issue. The internal electrical connection between V- and thermal pad is poor to moderate. The pad is metal and the silicon die sits on the metal with a mounting compound in between. Mounting compounds are thermally conductive and they are usually electrically conductive too. The sides and bottom of the silicon die have a potential path to V- pin node. This is why the pad must be left open or connected to V- pin directly. The pad is not a replacement for V- pin because the pad resistance to die is higher than V- pin resistance to die. This is why V- current is higher and not shorted out. I expect that the grounded pad to V- current may not be the same for all 50 units (current probably not shared equally)