TPS54308: TPS54308: BOOTSTAP

Evgeni Gofman

Part Number: TPS54308

Hi All,

I am using the TPS54308 for a 24V to 5V design.

All my calculations converge to the simulations and all is perfect except one thing.

in the DS, it says that BOOT-SW voltage should be -0.3V to 7V.

Looking at the DS and the internal design of TPS54308 it looks like this voltage is something internally 
and my responsibility is to provide the needed capacitor to store the needed energy.

in the simulation I measure 25.8 Volt which is way higher than 7V.
what's is the cause ? how can i fix it?

tina_ti_imulation - autosave 24-04-11 12_49 - autosave 24-04-16 09_32.TSC

7 months ago

0 Gui He 7 months ago

TI__Mastermind 20696 points

Did you measured the BST to GND voltage or the BST to SW voltage?

Thanks and best regards.

0 Evgeni Gofman 7 months ago in reply to Gui He

Prodigy 90 points

HI,

Both.

PH to SW- measured 25V .

PH to GND - 50V.

you can see it in the photo I've added.

0 Gui He 7 months ago in reply to Evgeni Gofman

TI__Mastermind 20696 points

Hi Evgeni

Sorry for the inconvenience, There should be something wrong with the BOOT Charge module integrated in the model. The BOOT cap is charged by an internal VCC , which is a voltage with value<7V, it seems the model is charging the BOOT cap using the Vin voltage though. You can ignore this, I will check with JIRA team try rectifying this. I can also help test on the TPS54308EVM and check the BST-SW voltage if needed.

Thanks and best regards.