TPS7A4001: Schematic review

Hi David, 

The configuration looks ok. This device needs an effective capacitance of 4.7uF for the output, therefore, having 9.5uF should be sufficient. In the case that this is really a concern, perhaps adding a 1uF rather than a 10uF. 

As for the input, the required minimum capacitance is 1uF, therefore, another cap is required, perhaps a 1uF||100nF with a 2.2uF. 

How much ripple is expected from the flyback converter? 

Best, 

Edgar Acosta

Hi Edgar,

if i use 1u || 1u || 100n then this is effective over 1uF, but how do you explain this TI reference design that has only 470nF effective capacitance on input?

PSEMTHR24EVM-081 /  TIDA-050026 / PSIL081

We expect 100mVpp like on this design

https://www.ti.com/lit/ug/tidt115/tidt115.pdf?ts=1656057612473

Best Regards,

David.

Hi David, 

Reference designs serve as a starting point and guidance to customers. 

In addition, the reference design only shows a 1uF rated for 100V, although an estimation could be made, it is hard to tell how much it will de-rate without exact part number.

It is common to see that a capacitor is selected with the exact minimum capacitance value. 

With 100mVpp, you should be ok without any filter.

Best, 

Edgar Acosta

Hi Edgar,

here is the PN from BOM 

C46 4 1uF 12061C105KAT2A AVX CAP, CERM, 1 μF, 100 V,+/- 10%, X7R, 1206

and VPWR is 55V

Best Regards,

David.