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TPS552892-Q1: VCC test check

Lanxi Li
Expert 6385 points
Part Number: TPS552892-Q1

Hello team,

My customer is doing the test as below:

They use the external supply to VCC pin, EXTVCC pull low. But at real test, they disconnect VCC pin to 5V supply.

Here is their test result:

VCC would have a small raise follow Vin, then with the EN pin pull up, the VCC pin will keep at 1.2V. You can see the waveform as below.

Question:

1. Does VCC voltage come from Vin even choose external supply? Please help explain the voltage change in the waveform.

2. Will this 1.2V influence the IC work normally? Please help evaluate the risk here.

Best regards,

Lanxi

  • 0
    TI__Mastermind 34201 points

    Hi Lanxi,

    1. When EN=high, the device will regulate the VCC voltage to 1.2V first no matter EXTVCC is connected to VCC,  floating or 0V. The reason is in the case of EXTVCC is connected to VCC (select internal LDO), if VCC is not regulated to 1.2V (above EXTVCC input logic high threshold), the device cannot select internal LDO.

    2. There is no risk of the 1.2V on VCC. When selecting external supply for VCC, a 5V needs to connected to VCC pin.