Adjustable current mode controller IC

[cts_casemod]

Hi,

I'm looking for a current mode controller (such as UC3842 or MC34063) in which I can have acess to the inverting input of the amplifier used for current measurement. The idea is to change the current by varying the reference voltage at which the comparator triggers, rather than having to use a potentiometer to vary the signal from the shunt resistor. Anyone aware of such a device?

Regards.

 

[KlausST]

Hi,

i think you don´t need a special controller.
Just "manipulate" the currrent measurement.

With MC34063 for example you could add a 100 Ohms reisistor (from shunt) in series to pin7.
You can build a simple current source (controlled by DAC or pot) to draw 0...3mA directely at pin7. This manipulates the current limit threshold to 100% down to 0% current imit.
With the current source of 0...3mA you pull down the Pin7 voltage by 0...300mV.

Klaus