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TPS65185：VGL ISSUE

Huang jenfu
Prodigy 10 points
Part Number: TPS65185

VGL issue
IC Name: TPS651851
Application: 13.3" e-paper
Question: I'm designing a power supply board for e-paper. The voltage input/output is as follows:
VIN: 5V
LDO1 (VPOS): +15V
LDO2 (VNEG): -15V
CP1 (VDDH): +25V
CP2 (VGL): -20V

Vcom set (I2c): -5V~0V
The reference circuit is as follows:

After exposure to 60°C, the VGL voltage changes from -18V to 17V. Could an experienced engineer tell me where the problem lies? Thank you.

I tried a few things (experiments):
1. Replaced the VGL C66 CAP (4.7uF) from 35V to 50V.
2. Increased VGH from 25V to 27V.
3. If there's a problem with VGL, the voltage is reduced to -18V and cannot be restored unless the TPS651851 is replaced. Finally, the output returned to normal.

  • 0
    TI__Mastermind 29615 points

    您好，已经收到了您的案例，调查需要些时间，感谢您的耐心等待。

  • 0
    TI__Mastermind 29615 points

    Hi, 

    Please be aware that TPS65185 is an older device, and may have limited support.
    I will still try my best to help with debugging this issue. 

    Does removing or reducing resistance value of R46 at VEE_DIS will have any effect?

    There is already internal 1kOhm resistor for discharge, and our EVM design just has a 0 ohm resistor here between VEE_DIS and VEE. 

    Else, is I2C being used in their system? -17V and even -18V should be out of power good range, is there any reaction on PWR_GOOD pin or VEE_PG bit in PG register?

    Is undervoltage being detected in VEE_UV bit of INT2 Register?

  • 0 回复 Lydia
    Prodigy 10 points

    Is it possible that the TS pin is unconnected?
    My circuit doesn't have a temperature sensor connected.
    If there's no temperature sensor, is the correct circuit to use a resistor connected to ground?
    What value should this resistor be?

  • 0 回复 Huang jenfu
    TI__Mastermind 29615 points

    Hi, 

    If TS is unused, please still have 43kOhm resistor connected from TS pin to GND.

  • 0 回复 Lydia
    Prodigy 10 points

    Hi Lydia:

    Is the VGL issue caused by the lack of resistor grounding on the TS?

    Can you explain why?

  • 0 回复 Lydia
    Prodigy 10 points

    Hi Lydia:

       There is already internal 1kOhm resistor for discharge, and our EVM design just has a 0 ohm resistor here between VEE_DIS and VEE.

     For example, in my circuit, VEE_DIS is a 750K resistor. Is this a VGL Fail issue?

    If so, what is the cause?

    Thanks.

  • 0 回复 Huang jenfu
    TI__Mastermind 29615 points

    Hi, 

    I do not suspect that the TS resistor is the cause of the VGL issue, but I cannot confirm.
    This is just the recommended connection, to have the 43 kOhm to GND, for best device performance.
    Customer can evaluate on their own hardware by seeing if this solves the issue, but I am unsure if it will solve it. 

    Best Regards, 

    Lydia