LTM4623 Multiphase Operation

Hello,

I am using two LTM4623 DC converters that share the same VIN [5V]. This VIN is coming from an output of another wide input Buck DC converter (1st Stage) that is taking a 36V and transforming it to 5V.

So the LTM4623 share the same VIN=5V rail:

- First LTM4623 converts from VIN=5V to 3.3V

- Second LTM4623 converts from VIN=5V to 1.1V

Can we use some phase relationship (in-phase or out-of-phase) by connecting CLKOUT to CLKIN to reduce the power demand on the VIN power rail?

Any proposal regarding the phase relation between the two converters to reduce the EMI radiations on the board or also to reduce the Vout ripple of each converter?



Adding a Figure to illustrate the question.
[edited by: Jawad at 11:56 AM (GMT -5) on 9 Dec 2020]
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  • Hi Jawad, 

    Generally for 2 phase operation it would be recommended to tie the PHMODE pin of the first module to INTVCC to program its CLKIN - CLKOUT relationship for 180 degree phase shift, then tie that CLKOUT pin to the CLKIN pin of the 2nd module. This can help minimize input current ripple on the input capacitor,for the high di/dt noise source. For reducing output ripple further may require using all ceramic, an output LC filter, or LDO depending on your output noise requirements. 

    Thanks 

Reply
  • Hi Jawad, 

    Generally for 2 phase operation it would be recommended to tie the PHMODE pin of the first module to INTVCC to program its CLKIN - CLKOUT relationship for 180 degree phase shift, then tie that CLKOUT pin to the CLKIN pin of the 2nd module. This can help minimize input current ripple on the input capacitor,for the high di/dt noise source. For reducing output ripple further may require using all ceramic, an output LC filter, or LDO depending on your output noise requirements. 

    Thanks 

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