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Two Synchronous Buck converters in parallel...one external error amplifier between them

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zenerbjt

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No.
The offset differences will likely mean one converter will try to deliver all the output current.
If you need to operate them in parallel, then each would need it's own feedback op amp circuit, and you would need to add a small series resistance in each of their outputs to balance the load (of course this will reduce the load regulation accuracy) .

Much better is to use a higher current converter, so you only need one.
 
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If the error amp output is the current control
signal then current sharing happens with a
small-ish mismatch error. However if it's a
voltage mode buck there could be gross
mismatch in delivered current.

What the "synthetic ramp current mode control"
holds, in this respect, I have no idea. Seems a
bit fancy, sampled and processed, to say. I'd
want a spec for current vs error amp output,
with upper and lower limits, near the big end,
to say whether imbalance was 5% or 50%.
 
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The offset differences will likely mean one converter will try to deliver all the output current.
Click to expand...
Thanks, from the controller block diagram on page 13, it is indeed evident that there is a 1V reference voltage leading into the inverting input of the PWM comparator. If there is a wide tolerance on this voltage from part to part, then of course, you are very correct.
The datasheet unfortunately doesn’t allure to the part to part tolerance of this 1V reference.
Thanks dick_freebird, just seen your response, yes, there will indeed be other tolerances in play in the ramp control circuitry that you describe.
Looks like this chip isnt up for paralleling.
 

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