TPS65400-Q1: obtaining loop parameters

Hi bob!

These internal loop related values are all in Datasheet. Could you please make a description about  Rs, As, Aol, GBWP and Vslope? You know one parameter always have many different symbol.

Shuai

here are the parameters from the TI tool i'm trying to use.  they don't exactly match anything from the data sheet.

or this:

if i take the webench loop suggestions they are quite different from the equations in the data sheet, or from the loop calc's i tried.

Hi Bob,

My colleague will give you reply soon!

BRs

Zixu

Hi Bob!

What is your application parameters, such as the input, output. We can help to calculate the compensation.

Shuai

vin- 9v to 16v

Vout-1.8v

nom Iout - 0.5a

we're also having trouble with the switcher locking.  we're using 6.8uH inductor, and 20uF Cout.  it would help to get a conservative compensation just to get it started properly.  

for the other rails-  

sw1-  Vin-9v to 16v

vout- 3.3v

Iout - 0.3a

inductor- 15uH, Cout- 20uF

sw2 - Vin 9v to 16v

Vout- 1.2v

Iout - 2.3a

inductor - 1.2uH, Cout- 44uF

sw4 - Vin 9v to 16v

Vout - 2.5v

Iout - 0.1a

inductor 33uH, Cout - 20uF

Vout- 1.8 is on the sw3 rail.

Hi Bob,

My colleague will give you reply by tomorrow!

BRs

Zixu

it's been 27 days.  can somebody get to this?  thanks!

Cout's are derated from 20 uF (X7S 2x10uF) to 18uF and from 44uF (X7T 2x22uF) to 42uF.  when i enter the EVM parameters into the Loop Calculator i don't get very good phase margin,  i had opened a separate ticket to answer some questions about the Loop Calculator design parameters.  that's still in progress.

we found the problem with the 1.8v rail not regulating was due to the pull ups on the SS lines interfering with the startup.  so we don't want/can't use the dual purpose softstart/power good feature for power good.  only the softstart option should be used.

Hi

What is your switching frequency!

Shuai