2A LED current driver with high-side resistor and current reporting

Hi Andrew,

Your design sounds interesting. May I know why you have to do this?

In fact, if just considering of  voltage/current/high side sense resistor, we have similar device in development. But I'm not familiar with current usage feedback that you described, I'm not sure if this device proper. Would you mind giving some block diagram to make me understand better? Thanks!

Robin

Hi,

I have three current controlled outputs, two are LED and the other is USB. The high-side is required to detect short, the analog is for the USB. The current draw is reported to a MCU. The current is controlled by MCU but voltage is free (input voltage is 5v). Resolution ideally needs to be 20mA steps up to 2A. I tried hysteresis mode current control but it's too problematic at low current.

I found Texas SLVA419d which discusses the approach, 100% on what I'm attempting to do, however when running what it suggests through TINA I can not make any variation of resistors or DAC voltage work correctly. It works great until the vRef/DAC source is connected then it becomes an all or nothing. Spent all of yesterday on it.

Regards,

Andrew

slva419d.pdf

sims.zip

dacR is a PWM from 0-3V. I've tried the dac/adj on both neg and pos side of the op-amp.

Hi,

So you want to achieve the constant output current with voltage regulator?

Robin

Hi,

Why AMP is necessary? How about this solution (section9.2.2 in TPS61165 datasheet).

Robin

It's required because the resistor is high side sensing.

Hi,

For low side sense resistor, you can also sample the sense voltage to MCU. And what's better, you do not need use differential method. and it's  more simple. Is there any misunderstanding?

Robin