TPS62560: Phase margin confirmation

Hi Moheddin,

Thank you for your reply.

I understand that our checking method is correct.

I found that there is some higher voltage than 7V at SW1, in order to resolve the voltage, we decided to change the multipliers against TI recommendation.

At that time, we checked the phase margin, it had around 60 degree.

Omitted the background about this inquiries,

I found IC106 broken due to a short circuit between #1(SW)-#6(GND) in the market.

Estimation cause is that there was no (phase) margin in the circuit, and synchronization could not be achieved, then a large voltage was applied to the SW terminal.

Therefore we would like to know the phase margin.

Could you please let me know the phase margin?

[Case1] Vout:3.3V, R1:8kohm, R2:1.8kohm, C1:1000pF　*Current our product circuit

[Case2] Vout:3.3V, R1:810kohm, R2:270kohm, C1:22pF　*Reccomendation of data sheet

Thanks & Regards,

Mishima

Hello Mishima,

Thank you for sharing more information.

?? ? said:

At that time, we checked the phase margin, it had around 60 degree.

The phase margin looks good and It doesn't seem that, this cause the short circuit between #1(SW)-#6(GND)

?? ? said:

Could you please let me know the phase margin?

[Case1] Vout:3.3V, R1:8kohm, R2:1.8kohm, C1:1000pF　*Current our product circuit

[Case2] Vout:3.3V, R1:810kohm, R2:270kohm, C1:22pF　*Reccomendation of data sheet

I can do the measurements but It takes some time as I don't have EVM for this device in hand.

In general I don't see this problem is due to phase margin of the device, as 60 degree look good to me, If the phase margin is too low and in that case there might me be some oscillations and that might cause the failure of the device.

Can you please provide me more information about the operating condition when the failure is happened.

Thank you & regards,

Moheddin.

Hi Moheddin,

Thank you for your comments.

> In general I don't see this problem is due to phase margin of the device, as 60 degree look good to me

The phase margin is around 60 degree what measured by our agent in few years ago.

We checked their reports, but it doesn't clear the measurement points.

We want to remeasure the phase margin again.

> Can you please provide me more information about the operating condition when the failure is happened.

1) We have not never found IC106 broken in the manufacturing process.

2) We found the IC106 broken symptom when the instration (First turn on in the market)

3) We replaced the IC106 of the returned product, but the symptoms have not recurred.

I understand that you don't have EVM(Evaluation board), could you please sumilate the phase margin by TINA application?

Your support is highly appreciated.

Thanks & Regards,

Mishima

Hello Mishima,

?? ? said:

I understand that you don't have EVM(Evaluation board), could you please sumilate the phase margin by TINA application?

For more practical results I would prefer the EVM, I ordered the EVM and will get in 3 to 4 days, I can do the measurements and provide you the results as soon as I got the EVM's.

?? ? said:

I found IC106 broken due to a short circuit between #1(SW)-#6(GND) in the market.

I guess it's related to higher voltage spikes on VIN or SW which is making the LS-FET to damage. Anyhow let me do the measurements and sort out the hypotheses.

Thank you & regards,

Moheddin.

Hi Moheddin,

Thank you for your cooperation and understanding!

> I guess it's related to higher voltage spikes on VIN or SW which is making the LS-FET to damage. Anyhow let me do the measurements and sort out the hypotheses.

When I tried inputting a high voltage to Vin, the High & Low FET were shorted. Therefore, this case is not consistent with the market problem.

As a result of inputting a high voltage to SW1, the Low FET was shorted.

Anyway I wait for your measurement.

Thanks & Regards,

Mishima

Hello Mishima,

I will update you after finishing the measurements.

Thank you & regards,

Moheddin.

Hi Moheddin,

Excuse me, I wrong the multiplirs.
Could you measure following?

[Case1] Vout:3.3V, R1:8kohm, R2:1.8kohm, C1:1000pF　*Current our product circuit

[Case2] Vout:3.3V, R1:810kohm, R2:180kohm, C1:22pF　*Reccomendation of data sheet

Best regards,

Mishima

Hello Mishima,

Unfortunately Moheddin is out today but he will provide the results with the new settings beginning of next week.

Best regards,

Sepp

Hello Moheddin,

Thank you for the checking!!

Could you please let me know Waveform data or value of phase margin for both case?

After confirmation, i want to resolved this sunject.

Thanks and Regards

Mishima