I have a need to implement a level shifter that transforms a ratiometric sensor output (a % of about 5V) to another ratiometric level (the same percentage of about 3V6). Note that neither the 5V nor the 3V6 are necessarily accurate or a constant ratio to each other. So, I basically need a circuit that implements:

Vout = Vin * ( V3 / V5) where V3 is the nominal 3V6 rail and V5 is the nominal 5V rail.

i.e. I need a variable gain stage where the gain is a function of the ratio of the actual supply rails (not a fixed gain using the ratio of the nominal rail voltages).

I'd appreciate any pointers...

TIA, JohnH

Edit: BW requirement is low (maybe up to 10Hz); accuracy better than 0.1%

 

Something like this chip might be able to do what you want.

 

Something like this chip might be able to do what you want.

Thanks for the pointer - looks like it would be perfect, if only:

• I had a negative supply rail available...
• I could justify the cost (the cost of the AD538 would kill my project)
• It came in a small SMT package (I need to integrate the solution in-line in a cable)

You've crystallized my thoughts, though: it might ultimately be easiest to locate a suitable micro-controller that has a separate AREF input for its ADC, digitize the input and then use a PWM drive to create the outgoing signal. 12 bits should be accurate enough so I don't imagine that finding a suitable uC will be too difficult.

 

it might ultimately be easiest to locate a suitable micro-controller that has a separate AREF input for its ADC, digitize the input and then use a PWM drive to create the outgoing signal.

Given your very modest bandwidth needs, I agree this may be the best solution.