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TPS2113A issue when IN1 ~ IN2

Balaji Krishnan
Prodigy 40 points
Other Parts Discussed in Thread: TPS2113A

I am testing out the TPS2113A device on a breadboard. The current limit is set to 1A (Rilim=500R). The OUT pin is connected to an electronic load (set as a 900mA constant current load), IN1 is supplied from a programmable DC source and IN2 is supplied by a single cell Li-ion battery. 

When I set IN1 ~ IN2, the output voltage (3V mean) is < IN1 (4V) and IN2 (3.9V) (image of waveform attached) and the device starts to heat up. 

Any suggestions/help would be welcome.

  • 0
    TI__Intellectual 2980 points
    Hello Balaji Krishnan
    Please send me the your schematic.
    Did you try this test with our EVM?

    Regards
    Dinesh
  • 0 in reply to Dinesh Kumar6
    Prodigy 40 points

    The circuit was made on a breadboard. I am using the TSSOP version of the device mounted on a breakout board. The schematic used is attached.

    VDC is a programmable DC supply while VBAT is a 3.7V (nominal) Li-Ion battery. 

  • 0 in reply to Dinesh Kumar6
    Prodigy 40 points
    No, I have not used the EVM; but since the device normally does not need to dissipate a lot of heat, I should not see any anomalies with my setup. The wire connections are good and the device performs well when IN1 and IN2 are well separated.
  • 0 in reply to Dinesh Kumar6
    Prodigy 40 points

    An update: At small loads (200mA) I find no problems but when I increase load current to 500mA, the device switches between the two supplies repeatedly. I have included the voltage waveform across a 0.1R current sense resistor on the IN1 (VDC) line @500mA load current.

    I suspect that the situation arises because VBAT drops significantly under heavy load currents causing the device to switch back to VDC; then when the no load voltage of the battery reaches a value > VDC + Vth the device switches back to VBAT and the process repeats. The losses associated with this continuous switching probably cause the device to heat up.

    Any validation of the above hypothesis as well as ways to offset it would be welcome.

  • 0 in reply to Balaji Krishnan
    TI__Intellectual 2980 points
    Could you please send me the IN1 & IN2 and Iout waveform together.
    Just to be sure , Please recheck the Input is not dropping when you draw power at 500mA load current.

    Regards
    Dinesh