For several reasons, I am going to replace UCC1895 controller with UCC28950. This design is in several hundred mission critical systems but life-cycle issues have brought up things to change.
One is the FBPS controller. There are some differences I notice.
Some clarification will help make the transition seamless
- RSUM function: legacy circuit had elaborate "slope compenstion" although I do not think it is necessary in FBPS case. So I can remove the glue circuitry around it. But how does RSUM differ & what advantages one has?
- Legacy design behaved a bit nervously in DCM. Our load is only dcm-ccm i.e. a pulse load . What is the dynamics of this pin function. What do I need to do extra to verify the new design will be "better"?
- No PGND: will this affect routing?
-Legacy had "average current mode" control with sharebus functions added. There are 20 such modules in parallel with total output capacitor approx 3600 uF( load is 1600 amp) output is 600 kHz. 28950 seems to be more suited for peak current control. This may require changes I cannot implement. So will 28950 function in same way as avg ctrl did with 1895?
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