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tps65185: tps65185 troubleshooting

ARSADHUSAIM MOMIN
Prodigy 150 points
Part Number: TPS65185

hello,

we are working on Eink display and we used PMIC TPS65185 for that please see below is our schematic.

we used imx7 processor for communication with eink.

we have facing some issue on that PMIC below is our issue on TPS65185.

- for powerup all rail and IIC communication we high WAKEUP pin and low POWERUP pin. it then we configure all register POWERUP, VNEG, VEE, VPOS, VDDH, is enabled using resistor. then we take PMIC into active mode.

- but internal booster DCDC1 and DCDC2 is in regulation. and VNEG and VEE is also in regulation but VPOS and VDDH is not in regulation.

- we check int2 register and its get error 10h so VPOS_UV interput come from IC because of VPOS is only generate 2.5V .

- for that we check internal register VCOM_EN which is high.

please see below is our schematic.

please explain why VPOS and VDDH is not in regulation.

  • 0
    TI__Genius 10885 points

    Hi,

    VPOS has a soft start current limit ~50mA, where it seems to stay in constant current mode until regulation voltage is reached. Is the output staying at 2.5V or slowly rising?

    Staying at 2.5V might indicate a ~50ohm load to gnd on that rail.

    Best Regards,

    Rick S.

  • 0 in reply to Richard Solarski
    Prodigy 150 points

    hello,

    thanks for your reply,

    output spikes to 3.7V and keeps falling. and we have not connect any load on any rail.

    and that voltage is not stying.

    thanks,

  • 0 in reply to ARSADHUSAIM MOMIN
    TI__Genius 10885 points

    Can you measure the impedance on that rail? It still sounds like the LDO is overloaded. Removing any additional components on that rail might help.

    The TPS651851 is pin-to-pin compatible with the TPS65185, with a slightly higher current capability, but since this occurs during soft-start/startup it may still behave similarly.

    Best Regards,

    Rick S.

  • 0 in reply to Richard Solarski
    Prodigy 150 points

    hello,

    please see my schematic i am not connecting any additional components on VPOS rail.

    because we have only two rail for VPOS one is input and i check that is +16V from DCDC1 and from output side i connect only 4.7uf capacitor which is recommended

    thanks,

    .

  • 0 in reply to ARSADHUSAIM MOMIN
    TI__Genius 10885 points
    Were you able to confirm the impedance of VPOS in case there is a layout/fabrication issue?

    Can you confirm how many TPS65185s/boards have been tried with this layout and experienced the same issue?

    Best Regards,
    Rick S.
  • 0 in reply to Richard Solarski
    Prodigy 150 points

    hello,

    we will connect all rail with jumper wire and i will also check all pin to pin connection on connector side so it is not shorting on any pin.

    after connecting all pin with GPIO then all voltage is generated.

    please see our connector schematic. below if we need to change anything and then work.......

    you can compare it with our schematic

    we also check all require GPIO  using high low functionality it will work fine so its dont have GPIO issue.

    so after connecting PMIC on connector then why VPOS is not generating so if impedance trace issue is here then it will not work with jumper also.

    i dont know why this VPOS is not generating.

    please help asap,

    thanks,

    arsadhusain

  • 0 in reply to ARSADHUSAIM MOMIN
    TI__Genius 10885 points

    Arsadhusain,

    If I understand correctly, this connector supplies the PMIC, and VPOS functions properly when it is replaced with jumpers, is this correct?

    How was 5V0 applied to the PMIC during the GPIO test? Does it behave differently when supplied through the connector?

    Best Regards,

    Rick S.

  • 0 in reply to Richard Solarski
    Prodigy 150 points

    hello ricks,

    thanks for your great understanding,

    yes correct.

    5V0 we connect from imx7 sabre board using jumper wire.

    best regards,

    arsadhusain momin