TPS2120: TPS2120 VIN1 switch to VIN2 problem

YULUNG HSU

Prodigy 60 points

Part Number: TPS2120

Tool/software:

Hi Sir,

We found a problem on VIN1 switch to VIN2 when PR1 voltage lower Vref.

The VIN1 is 12V+-10% and VIN2 is 12V+-2%, please check the schematic drawing as below:

Because of we set the VIN1 priority than VIN2, when we plug out VIN1 power source we found sometimes Vout will change to VIN2 then change back to VIN1.

Please check the below picture and we would like to know how to fix this issue?

Yellow line is PR1 pin and green line is Vout.

Thanks,

Ocean

5 months ago

0 Kunal Goel 5 months ago

TI__Guru* 79181 points

Hi Ocean,

Please let me check and get back.

Regards

Kunal Goel

0 YULUNG HSU 5 months ago in reply to Kunal Goel

Prodigy 60 points

Hi Kunal,

Do you have any update information about this issue?

Thanks,

Ocean

0 Kunal Goel 5 months ago in reply to YULUNG HSU

TI__Guru* 79181 points

Hi Ocean,

Is this repeatable everytime or sometime ?

Do you have caps on vin pins?

Regards

Kunal Goel

0 YULUNG HSU 5 months ago in reply to Kunal Goel

Prodigy 60 points

Hi Kunal,

This problem can't be duplicated every time but sometimes happened.

We have 220uF E-Cap near the DC jack, but this problem always happen when we remove AC adapter power source from AC outlet.

If we remove AC adapter from DC jack, there is no such issue.

Thanks,

Ocean

0 Kunal Goel 4 months ago in reply to YULUNG HSU

TI__Guru* 79181 points

Hi Ocean,

Can you try adding more ceramic cap near vin1 and vin2 pins?

Regards

Kunal Goel

0 YULUNG HSU 4 months ago in reply to Kunal Goel

Prodigy 60 points

Hi Kunal,

I tried to add more ceramic caps near Vin1 and Vin2 pins, but it still no any improve about this issue.

BR,

Ocean

0 Kunal Goel 4 months ago in reply to YULUNG HSU

TI__Guru* 79181 points

Hi Ocean,

Let me think more on it.

Regards

Kunal Goel

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TPS2120: TPS2120 VIN1 switch to VIN2 problem