UC3845 - voltage feedback comparator speed (pin 2)?

[MacIntoshCZ]

Hello,
does anyone know bandwith of this comparator in uc3845?
I just measured voltage response and its kinda slow... =D
10khz i guess?

 

[Nigel Goodwin]

Isn't that a switch-mode IC?, presumably it's as fast as it needs to be.

 

[MacIntoshCZ]

It is. Do you think its good combo to have 500khz current sense comparator and 10khz voltage feedback comparator?

 

[Nigel Goodwin]

It is. Do you think its good combo to have 500khz current sense comparator and 10khz voltage feedback comparator?

I don't think it's a good idea to have too fast a feedback loop, so 10KHz is probably more than fast enough.

 

[MacIntoshCZ]

thanks

 

[ronsimpson]

I don't understand the question. The error amp has a unity bandwidth of 1mhz. The current comparitor has a 150nS delay.
In normal operations the error amp has Rs and Cs around it to slow it down.
The current compar function normally has a RC to remove fast spikes. (maybe 100nS)

Do you think its good combo to have 500khz current sense comparator and 10khz voltage feedback comparator?

The error amp should take 10s to 100s of cycles to move the voltage. The current sense needs to work in a small fraction of a cycle.

 

[MacIntoshCZ]

I don't understand the question. The error amp has a unity bandwidth of 1mhz. The current comparitor has a 150nS delay.
In normal operations the error amp has Rs and Cs around it to slow it down.
The current compar function normally has a RC to remove fast spikes. (maybe 100nS)

The error amp should take 10s to 100s of cycles to move the voltage. The current sense needs to work in a small fraction of a cycle.

Thanks for answer. Even without understanding quistion you hit the point =).