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Current mode controller giving external access to both PWM comparator inputs?

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treez

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Why is the MCP1630 the only current mode control chip in the world that allows one to directly set the voltage on the PWM comparator input? (ie so that one can set the peak inductor current).
Chips like the UCC28C43 make this impossible as they have diodes in the way.

MCP1630 datasheet:
https://ww1.microchip.com/downloads/en/DeviceDoc/21896C.pdf

I appreciate the HV9910B has an accessible PWM comparator input but the reference is fixed and set too low for us..being just 0.25V…we need it to be 0.5 to 1V….or externally adjustable.

HV9910B
https://ww1.microchip.com/downloads/en/DeviceDoc/20005344A.pdf
 

Hi,

...But what could we fiddle with to reach Rome? :) Not possible to adjust the CS pin input (It's that one where you'll input your signal, is it?) to a level that matches the reference with a resistor voltage divider or better yet an op amp (inverting gain)?
 
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An SMPS microcontroller with a fast PWM comparator inside it would be good, but all the micro's i see have slow comparators inside them.
Woudl prefer an anlalog chip though , if it existed.
 

The peak threshold is low so that losses from the current sense resistor are minimized. This is also why those dividers/diodes are used on the error amplifier output (to provide a 0-0.25V control signal from an amplifier with a much higher supply voltage).

In other controllers (mainly from LT) an amplifier is used on the CS pin to boost its voltage to match the operating range of the error amplifier.

If you really direct access to that many internal nodes, then you might as well roll a discrete controller. Or maybe use an external comparator which drives the CS pin of the control chip. That way you could still make use of the oscillator, latch, and driver in the control chip.
 
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