TPS548A29: Buck Recommendation

d_zero

Genius 4670 points

Part Number: TPS548A29
Other Parts Discussed in Thread: TPS543820

Dear *,

we have to generate 0.8V from 5V with following specification:

Iout_max = 7A

Vout = 0.8V

Vin = 5V

Ripple mVp-p = 24mV

good transient response

Would you recommend TPS548A29, or do you suggest any other device?

Some designs use LTC3310S, would you recommend TPS548A29 for replacement?

Best Regards,

David.

over 3 years ago

0 David_Daniels over 3 years ago

TI__Mastermind 20375 points

The TPS548A29 or the TPS543820 are good candidates.

Additionally, there are other devices to consider Link to ParameterSearch.

the devices can be filtered and compared using the parameter search.

0 d_zero over 3 years ago in reply to David_Daniels

Genius 4670 points

Hi David,

please can you review the attached schematic? Also can you tell which of the listed inductors would you pick for our application?

Power 0.8V.pdf

Best Regards,

David.

0 David_Daniels over 3 years ago in reply to d_zero

TI__Mastermind 20375 points

Looks good, I would add a resistor and capacitor in parallel with R162. The additional RC gives flexibility on improving transient response and stability.

See https://www.ti.com/lit/ds/symlink/tps548a29.pdf#page=40 for pcb layout example.

On page 39 are the layout recommendations and page 25 shows a schematic with the agnd and pgnd shown.

Following the layout recommendations and connect the sensitive analog components to AGND

0 d_zero over 3 years ago in reply to David_Daniels

Genius 4670 points

Hi David,

I added the additional resistor and capacitor footprints to the design.

thank for the response, please can you comment is it ok to have 10uF ( 0805 10 X7R) on pin 19 VCC for decoupling?

If no problem which inductor would you recommend form the listed ?

Br,

David.

0 David_Daniels over 3 years ago in reply to d_zero

TI__Mastermind 20375 points

10uF on VCC should be okay.

I prefer the SPM6530T-R25M230, some experience with it over the others.

It is shielded, has 2.3mohm and current rating of 23A.

If the VIN voltage is always lower than 5.3V, the VCC can be connected to VIN through a low value (1 to 10 ohm) resistor.

The VCC voltage is 4.5V, but can be overdriven externally. Using an external 5V on VCC, would have a slight improvement in system efficiency. The 5V drive would lower the on resistance of the fets and improve conduction losses.

0 d_zero over 3 years ago in reply to David_Daniels

Genius 4670 points

Hi David,

yes the Vin is always 5V, is it ok to use 10R 0402 resistor between VIn and VCC ?

Thank you for the inductor suggestion, we will try to also some others, eg. WLPM706630MR24LC

https://eu.mouser.com/ProductDetail/Walsin/WLPM706630MR24LC?qs=%2Fha2pyFadugvb0Joir76I%2FhhKseY%2FyuqDE%252BegpEw9kz%2FlTUl4KdBtg%3D%3D

the price is 5x less for1k units and has slight higher DCR.

I also fond this inductors that have DCR below 1mOhm SLR1050A-221KE , what do you think how much efficiency increase we can get from this low DCR?

Br,

David.

+1 David_Daniels over 3 years ago in reply to d_zero

TI__Mastermind 20375 points

The 0402 resistor from VIN to VCC is good.

To estimate efficiency, i preference is to use the webench.ti.com tool.

All the inductors listed are viable, the conduction loss will be lower with the 1mOhm rdc. The AC losses are difficult to estimate, so testing on the bench is a valuable to assessing the inductor.

Power management

Power management forum

TPS548A29: Buck Recommendation