Dear Sir.
We use TPS23754 to output 12V@2.5A.
PoE IN-> Ripple of output is about 200mV.
24VAC IN-> Ripple of output will run to about 2.6V.
Ripple is very different. How can I improve the problem that the 24VDC_IN Ripple is too high? Thanks for help~
Hello AJ,
It looks like in your schematic the power transformer is only rated for 33-57V input. This would imply that a 24V input is probably causing the transformer to saturate, and causing higher duty cycles and thus higher peak currents and ripple. My first suggestion would be to get a transformer that is rated to handle a wide-Vin. We have some reference designs in our library that support this if you need a reference to look at.
Another way, or rather an additional way you could address the issue is to add a output snubber like on PMP21318. The schematic can be found on this E2E post: 
Regards,
Michael Pahl
HI Michael,
1. I try to mimic the capacitance setting of PMP21318, but spike still at 2.6V
2. Could you tell me about transformer how to choose or how to change transformer input Voltage to right voltage, because I try to change transformer input to 30~55V, but spike no improvement, The input voltage need to be lower? The voltages on other pins need to be adjusted? (4-5, 6.7-9.10)
thanks.
