TPS552892: SW frequency

Hi Heater,

Thanks for reaching out on e2e.

1. May I know what is the application and customer here?

2. Could you reply with the schematic? What is the maximum output current?

3. Could you attach the waveforms of SW1, SW2, Vout, Vin, iL at 15Vin and 7Vin condition?

Regards,

Bryce

Hi Bryce,

1. May I know what is the application and customer here?

>> In automotive application

2. Could you reply with the schematic? What is the maximum output current?

Imax:1A

3. Could you attach the waveforms of SW1, SW2, Vout, Vin, iL at 15Vin and 7Vin condition?

>>15Vin \ no load as below:

Yello--Vo(AC coupling)、Green -- iL、Purple -- SW1、Blue -- SW2

>>7Vin / no load as below:

Yello -- SW2、Green -- SW1、Purple -- iL、Blue -- Vo(DC coupling)

Regards,

Qin

Hi Qin,

Thanks for your detailed waveforms. I think this is because of the unsuitable loop compensation parameters which caused unstable loop.

Please see my comments below and you can use the attached calculation tool to optimize the compensation by yourself too.

1. Per current compensation parameters, the phase margin is negative. Recommend to change R406=15k, C212=4.7nF.

2. Just curious, why do you prefer to use external 5V for VCC since EXTVCC is connected to GND?8585.TPS552892 Design Calculation V1.0.xlsx

Regards,

Bryce

Hi Bryce,

Thanks for your recommends, it helps me a lot.

using external 5V for VCC may help to reduce power loss since external 5V from BUCK DCDC convertor. 

another question：this chip already has COMP for external loop compensation, is it necessary to reserve C221 in feedback circuit？Can i delete it or better  reserve it?

Regards,

Qin