TPS564257: TPS564257 7.5v output inductor choice

Hi Rehards,

My colleague Lucia will reply you tommorow.

Thanks,

Colin

Hello,

I have read that but didn't mention inductor choice. I have got fantastic results using TPS564247 which got me about 5mv p-p total ripple figure without noise. 

I used 3x22u 1206 X5R caps + 5x10u 0805 X5R caps + 2x100nf 0402 caps + 1x10u high esr elec. cap (3 ohms for damping) in parallel as my output capacitance. the inductor was 2.2u with low resistance. I created a new prototype of the same circuit but replaces one 100nf with another 10u 0805 cap.

i want 7.5v output this time which is why i saw this device. another device i saw is TPS56637. however both have low switching frequency, since tps564247 has 1.2 mhz and these are 0.6 and 0.5 mhz which may require me to change the output capacitance or inductor.

please check what i posted here and give me your recommendations. I will never use elec. caps at output, only ceramics and maybe some solid polymers. 

Hello,

I figured 4.7u is the best choice too.

however, you mentioned checking stead-state operation, output ripple and load transient... how can i do it without building the prototype? i don't understand what you meant.

previously, i build the exact same circuit but for 5v using TPS564247 and it performed perfectly!! 3-5 mv p-p total ripple which is fantastic. is it safe to assume that with 7.5v using this regulator and more bigger caps (for dc bias) can get the same result?

Hi,

We are on Chinese holiday, will reply on 10/8. Thanks.