TPS65185: Power Up Troubleshooting

Vincent LINTILHAC

Part Number: TPS65185

Hi,

I'm using a TPS65185 chip to power up a E-ink screen (ED060) and I am having some issue powering up the EPDC. The device is set to ACTIVE through I2C communication.

With the screen unplugged, the power rails are in regulation.

(VN in Yellow - VNeg in Blue)

Otherwise, once the display is plugged into the connector, the PMIC doesn't power up and the interrupt register shows a VNeg under voltage error, and the Power Good register shows 0xA0 (when 0xFA without the display).

(VN in Yellow - VNeg in Blue)

I tried to increase the delay between the ramp up of the rail, without success. The only load on the rail is the EPDC (so I don't think the current exceed the capacity).

I tried different displays, and I experienced the same issue. Any idea of what could cause this problem?

Best,

Vincent

over 2 years ago

0 Gerard Copeland over 2 years ago

TI__Genius 10380 points

Hi Vincent,

Comments on the schematic:

4.7 uF input capacitor is recommended close to VDDH_IN
If using the V3P3 load switch, it can be beneficial to add input/output capacitors

I wouldn't expect either of these items to affect the VNEG LDO.

Can you confirm C53 is placed close to the VNEG pin on the PCB?
Do you have any way to measure the VNEG output current when during this startup issue?

Thanks,

Gerard

0 Erwan Kerebel over 2 years ago

Prodigy 10 points

Gerard Copeland Thank you for your response. My colleague Vincent is OOO until monday and he will follow-up then. In the mean time, I can confirm that C53 is close to TPS65185 (<3mm).

0 Alex Saenz over 2 years ago in reply to Erwan Kerebel

TI__Expert 6700 points

Erwan,

Gerard will be OOO until February 9th so he will not be able to respond to any further traffic on this until that time. I suggest we close the ticket for the time being but we can re-open it once Vincent follows up.

Regards,

Alex

0 Vincent LINTILHAC over 2 years ago in reply to Alex Saenz

Prodigy 70 points

Thanks for the answer !

The connector to the EPDC was mirrored causing the issue when the display was plugged in.

We are only using V3P3 for debugging. Concerning the input capacitor for VDDH_IN, C70 is close to the pin, let me know if I need to add another capacitor on this signal for better results.

Best,

Vincent

0 Gerard Copeland over 2 years ago in reply to Vincent LINTILHAC

TI__Genius 10380 points

Hi Vincent,

Great to hear you've found the cause of the issue. If C70 is close to VDDH_IN and the boost components are tightly placed, It's not necessary to add another capacitor.

Thanks,

Gerard

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TPS65185: Power Up Troubleshooting