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TPS63806: TPS63806 ocp limit

Part Number: TPS63806
Other Parts Discussed in Thread: TIDA-050017,


we use TPS63806 to drive TEC, just as TIDA-050017's solution, found that during Vin=3.3V, Vout=4V, Io>0.7A, the output current become unstable as below waveform, it's measured by current sensing probe, we doubt it hit the OCP limit.

So what's the accuracy OCP limit value? and the OCP protection mechanism?

  • Hi Lin,

    At Vin = 3.3 V, Vout = 4 V, the TPS63806 can supply much more than 0.7 A, so these oscillations shouldn't be caused by current limit.

    Are you using completely identical design (schematic, parts, PCB layout, code) as the TI design? If not, please provide additional information:

    • Show the schematic of your design.
    • Show the PCB layout of your design.
    • Is there a closed loop temperature control in your design?  

    Best regards,

  • Hi Milos,

    pls refer to the attachment, including the schematic and description, this test is on our TPS63806EVM, so the layout is same as this EVM.TPS63806-TEC Driver -.pptx

  • Hi Lin,

    I stopped at 3rd slide. It seems you don't have a resistor between the 22-µF capacitor and the FB pin. Did you forget to put R58 from the schematic, when you modified the EVM?

    Best regards,

  • Milos,

    it's a drawing mistake, actually it has a 80.6K resisitor in series in circuit.

    Pls help review this issue, looking forward to your reply. thanks.

  • Hi Lin,

    I didn't see any issue for Vin = 3.3 V and Vout = 4 V, with R = 1 Ω, when Iout = 0.7 A. At Iout = 0.7 A the device still operates in PFM mode and you should see some current ripple around 70 mApp. I also went up to Vout = 5 V, where I out= 1.8 A, and still no issues.

    Could you please answer one of my first questions - is there any closed loop temperature control, or you just have fixed PWM control signal? Can you try applying a DC voltage instead of the PWM signal? Start from 0.5 V and slowly reduce it to increase the output voltage.

    As for the case when you have different minimum Vout: When Vout < Vin, the device operates in reverse (it is sinking current), and the reverse current limit is typically 0.9 A (as stated in datasheet).

    • For R = 1 Ω, the minimum output voltage is limited to typically 3.3 V - 1 Ω * 0.9 A = 2.4 V.
    • For R = 2 Ω, the minimum output voltage should be limited to typically 3.3 V - 2 Ω * 0.9 A = 1.5 V, but this is less then the recommended minimum of Vout,min = 1.8 V.

    Best regards,

  • Hi Lin,

    We haven't heard back so we assume this answers your question. If not, just post a reply below, or create a new thread if the thread has locked due to time-out.

    Thanks and regards,