This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TPS2595: TPS2595 Quiescent Current

Part Number: TPS2595

I am using the TPS2595 as a fuse for a small battery pack.  The charger is setup to charge the battery through the pass transistor body diode and is current limited to 1.2A.  I am seeing some batteries fail QC checks after being stored briefly and was able to root cause it to an excessive current draw on the TPS2595.  To verify the UVLO resistor chain was not causing this, the upper resistor was removed, which should put the part in a low power mode.  I am seeing 28mA of quiescent draw though, with no output load and no charger connected.

I am trying to determine if the charge path through the body diode could cause this (not sure how it would), or what else could cause the current draw to be 1000X what is stated in the datasheet.  Any ideas on the root cause and how to abate the issue is much appreciated.

Thanks!

Al

  • Hi Alvaro,

    As per your problem description it seems that you are connecting the  charger(supply) to the output pin of TPS2595 and battery(load) to the input pin and measuring the current flow from OUT to GND of IC. Can you confirm on this?

    Would it be possible for you to share the schematic ,  Charger and Battery voltage and exact part number for better understanding ?

    Regards

    Kunal Goel

  • Kunal,

      Thanks for the reply. The battery is a 6.4V VRLA, and the charger is a 7.2V (max) supply with a current limit of 1.4A.  Please find a snapshot of the schematic below.  The current that I am measuring is with no output load and was taken between the battery and BATT_POS terminal shown in the schematic.  The GND is connected to the battery negative.

      We have also seen fallout of the UVLO circuit if the board is connected to the POS terminal of the battery before attaching the GND wire to the battery.  I believe this is caused by a brief over voltage condition on the UVLO pin when the ground is attached.  The board I am testing the excessive current draw with have been assembled with this in mind, and have also been tested with the upper resistor (R1) removed  to ensure it is not the cause of this issue.  This forces the board into UVLO operation which the data sheet indicates a current draw of < 1uA. One of the boards is showing a quiescent draw of 28mA in this configuration.

      

  • Hi Alvaro,

    Thanks for the explanation. The schematic snapshot is not attached properly. Could you please send the schematic again?

    Regards

    Kunal Goel

  • Hi Alvaro,

    I will get back to you by Monday.

    Regards

    Kunal Goel

  • Hi Alvaro,

    Forward biasing the body diode of pass transistor is not recommended for continuous use and it can be a risk to device .The internal VDS sensing blocks will cause excessive current flow even when device is disabled. 

    Regards

    Kunal Goel 

  • Okay, that confirms by suspicion. Now how to resolve this?  Would the addition of a Low Vf Schottky rectifier in parallel abate the concerns?  If not, I wil have to consider the power loss consideration of establishing a dual path solution, where charge current would not be fused.  Example of what I mean below:

  • Hi Alvaro,

    In configuration A the body diode will still be forward biased and will cause the excessive current issue . You can try configuration B ,it seems better solution.

    Regards

    Kunal Goel