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TPS65632 issue when used with AUO panel

Jerrison Wang
Prodigy 80 points
Other Parts Discussed in Thread: TPS65632

Could you kindly  help on TPS65632RTER issue?

>Background: when used TPS65632RTER with AUO 3.81’’panel ,part number:H381DLN01.0

> Issue details：

1.when the CTR-EN setting up , a little high voltage occurred in VNEG, and when CTR_EN is ready  VPOS dropped , pls see the waveform (image003, yellow ：VNEG     red ：VPOS    green：CTR_EN)

Tested the maximum current :Vpos is 240 m A and Vneg is 40mA

2.keep the Vpos connecting with the panel , disconnected Vneg(-2.9V) and connected EVSS with the electrical load ,set the load current at 9m A, then powered the TPS65632, Vpos  and Vneg  is 0V; with then same situation ,just set the load current at 5mA, Vpos and Vneg  can work normally  , see the wave form image 002 load current is  9m A; image 004 load current is 5mA; Green Vpos, yellow Vneg.

3.keep Vneg connecting with panel , disconnected Vpos  and connected Vneg  with the electrical load ,set the load current >1m A then powered TPS65632, Vpos and Vneg  is 0V

 

Why was  the load of EVSS above 5mA then powered TPS65632, Vpos  and Vneg is 0V?

The Vneg is set by the pulse signal in CTRL pin , if set the Vneg at -2.9V , it became -4.6v first and then turned to -2.9V, so for any  Vneg set  value  ,if it is became the default -4.6V then tuned to the set value?

Thanks

 

 

  • 0
    TI__Expert 8010 points
    Hello Zhen,

    Thanks for your enquiry. From your description I can filter out two problems:
    1) Device will shut-down when output current of 240 mA/40 mA is applied --> device is not designed to start-up in full mode.
    The load should be applied when the output voltages are already in regulation. Why does the customer test the device into full-load? Usually when the panel turns on it initializes the driver circuitry before it shows a picture (load).
    2) During start-up VNEG = -4.6 V and then only set to required voltage of VNEG = -2.9 V --> When CTRL is pulled high the converter will always start up with its default value of -4.0 V and only then it can be programmed to the desired voltage. Having said that i wonder why in your case the converter starts with -4.6 V...What are the other output voltages (AVDD, VPOS) at start-up?

    Best Regards,
    Ilona
  • 0 in reply to Ilona
    TI__Prodigy 80 points

    Hi Ilona

     

    as customer did a test : if the VNEG 's current is less than 5mA when power on  , VPOS and VNEG can work normally ,if >5mA ,VPOS and VREG can not work.

    customer add a serial resistor in the VNEG to reduce the power up current , it can work normally.

    customer wanted to know what is the maximum required current in VNEG and VPOS when in power on of TPS65632?

     if it exceed the max current limit , the VNEG and VPOS will be shut down ,right ?

    Thanks

  • 0 in reply to Jerrison Wang
    TI__Expert 8010 points
    Hello Zhen,

    The maximum load that you can connect between VPOS and VNEG during start-up is roughly 2.9 kOhm (~ 3 mA (typ)).
    The short-circuit protection (of VPOS and VNEG to each other) in this case does not monitor the switch current but the time and the voltages of the rails. If one of the voltages is not in regulation after a certain time after CTRL goes high (VPOS:10 ms, VNEG:20 ms) then the error is detected and the device will shut down. To resume the operation the input voltage needs to be toggled LOW and HIGH.

    For further information please read chapter 7.3.7 of the d/s. If something is not clear described there please let us know.

    Thank you.
    Best Regards,
    Ilona