LM5163: Buck converter not entering CCM, although WEBENCH and calc tool show that it should

Ilya Dontsov

Part Number: LM5163

I'm struggling with the buck converter (42V -> 19V, 70mA). I've done a calculation in the WEBENCH tool and it gave me the suggested circuit below. It implise that at 300kHz switching frequency and 70mA load the circuit should run in CCM. But it doesn't. It runs in DCM which is not what I need.

I tried increasing the frequency up to 500kHz, but it didn't change the mode to CCM. Where should I start looking?

over 4 years ago

0 Harrison Overturf over 4 years ago

TI__Genius 10695 points

Hello Ilya,

I created the Webench design below with the same parameters that you have in your design, however mine indicates the part is operating in CCM.

Can you check it out and confirm that the parameters are the same?

I also checked the parameters with the Quickstart calculator for the device and it too indicates that the device should be operating in CCM since the average output current is greater than half the output current ripple.

https://webench.ti.com/appinfo/webench/scripts/SDP.cgi?ID=7B19BA10CA45D639

Copy of LM5163, LM5164 Quickstart Calculator rev3.xlsm

Regards,

Harrison Overturf