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TPS65100-Q1: TPS65100-Q1 output drop issue and delay output time

Part Number: TPS65100-Q1
Other Parts Discussed in Thread: TPS65150-Q1

Dear,
ourl client use design TPS65100-Q1, but we find two question, schematic as below.

217EA01-1A0 _TPS65100QPWPRQ1.pdf

1. VDD=3V, output VGH was drop issue. Could you explain this phenomenon?

 Measurement Lxw) waveform:

2. VDD=3.3V , power up sequence : VGL early to VGH 355.55us , If we want VGL early to VGH 1ms even more time , how to realize schematic.

If any suggestion, Please advise me.

Thanks,

Best regards,

Lawrence.

  • Hello Lawrence,

    1. VGH phenomenon:
    I expect VDD is the input voltage VIN in the schematic, correct? At the moment when VGH shows the fluctuation, VDD seems to be very close to the UVLO voltage. I think the IC going into and out of UVLO during this fluctuations. To be absolutely sure, VDD, VGH, and C2+ and if possible the VGH load current should be monitored.
    A possible solution to this could be an RCD circuit connected to the EN pin to start the IC later, when the VIN is already higher.

    2. The startup of the TPS65100-q1 is fixed and only a switch between the output and the load turning off VGH could help to not apply it for 1ms to the load. Here the startup description from the TPS65100-q1 datasheet:
    If the enable pin EN is pulled high, the device starts its power-ON sequencing. The main boost converter starts
    up first with its soft start. If the output voltage has reached 91.25% of its output voltage, the negative charge
    pump comes up next. The negative charge pump starts with a soft start and when the output voltage has
    reached 91% of the nominal value, the positive charge pump comes up with a soft start.

    I would recommend to check the TPS65150-q1 which uses external capacitors to delay the outputs. Please check Figure 12 in the datasheet.

    Best regards,
    Brigitte
  • Hi,  Brigitte


    About 1 question add RDC circuit connected to th EN pin as like below chart?


    R and C Value, we will try 100ohm and 0.1uF to test.

     



    and we find the Datasheet EN pin trun high the min voltage was 1.5v  and then start  power up  , but we find the EN pin 0.8v was turn on. it`s normal status?

                                     麻煩協助確認是否有問題


     

    If any suggestion, Please advise me.

    Thanks,

    Best regards,

    Lawrence.

  • Hello Lawrence,

    1. Yes, the circuit you drew is almost correct. I recommend a diode in parallel to the resistor (cathode to VIN) because then the capacitor gets discharged through the diode if VIN falls. Otherwise it needs to get discharged through the resistor and this will take relatively long.
    2. The EN signal will get active somewhere between 0.4V and 1.5V, dependent on the input voltage and the temperature. So 0.8V is well within the specification.

    Best regards,
    Brigitte
  • HI, Brigitte

    I Got it, we wil try fast-switching Schottky diode(SDM03U40) in parallel with the resistor to test.

    If any suggestion, Please advise me.

    Thanks,

    Best regards,

    Lawrence.