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TPS61196: VIFB voltage

Guru 10835 points

Replies: 9

Views: 153

Part Number: TPS61196

Hi

May I ask about VIFB voltage since I couldn't find similar post regarding VIFB of TPS61196?

According to datasheet,the VIFB voltage is defined as "IFBV voltage setting range = 0.3 V to 1V".

If VIFB(min headroom voltage) is set by R10 to under 0.3V, what kind of phenomenon is concerned?

On the customer board, there are a failed case to start up at some device.

(Now R10 and R11 is 47kohm and 49kohm.)

Best Regards,

Koji Hamamoto

  • Hi K,
    The voltage drop on IFBx pin was used to provide enough headroom volatge for internal current sink to make sure this current sink can provide enough current. The minimum headroom voltage depends on how much current you need. if you don;'t provide enough headroom volatge, the current sink may fail in some situation. So what's the maximum current each channel that you need? And does your customer start up with full load?
    Regards
    Sean
  • In reply to Sean Zhou:

    Hi Sean,

    Thank you for your prompt reply.

    ILED is 100mA/ch. And yes, the duty was 100% when it fail at start up.
    What kind of phenomenon is concerned when VIFB is set at under 0.3V?

    Best Regards,
    Koji Hamamoto
  • In reply to K.Hamamoto:

    Hi KH,
    It may can't start up correctly, you can increase the R10 value and have try again, or you can try to decreat the duty when start up.
    Regards
    Sean
  • In reply to Sean Zhou:

    Hi Sean,

    Thank you ! I will suggest it to the customer.

    By the way, I do not understand why it may fail to start up when VIFBV is under 0.3V.
    What is the mechanism to make that fail case is occurred?

    Best Regards,
    Koji Hamamoto.
  • In reply to K.Hamamoto:

    Hi KH,
    0.3V is for about 100mA, in your situation you start up with full current, so you need to provide enough headroom voltage, there is an internal logic and control circuit for this comparision.
    Regards
    Sean
  • In reply to Sean Zhou:

    Hi Sean,

    Our customer modified to increase R10 to 150kohm but the cathode voltage is 150mV.

    On the other hand, if Vin is increased to 16V from 12V or if total output current is decreased to 500mA from 600mA, the cathode voltage became normal (around 340V).

    I do not understand what is this phenomenon and what is the root cause. Could you give us any advice?

    Best Regards,
    Koji Hamamoto
  • In reply to K.Hamamoto:

    Hi Koji,
    Could you share me the schematic form your custome?
    Regrads
    Sean
  • In reply to Sean Zhou:

    Hi Sean,

    I have schematic but it is a confidential information. Can we talk with email?
    If it ok, could you give me your address?

    Best Regards,
    Koji Hamamoto
  • In reply to K.Hamamoto:

    Hi Koji,
    You can send to me: sean-zhou@ti.com And please click "Resolve" for me. thanks.
    Regards
    Sean

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