Re: bipolar digital pot

> On 5/8/08, Mark Rages <markrages@...> wrote:
>> On Thu, May 8, 2008 at 11:45 AM, Martin <martin@...> wrote:
>>> I have an analog circuit that has a (normally) negative polarity DC
>>> feedback signal. I'd like to change the gain of the circuit digitally,
>>> so I'd like to use a digital pot. The problem is that a digital pot can
>>> only take signals between VEE and VDD - most usually probably 0v to 5v.
>>>
>>> My rails are +5/0/-5 and my feedback lies somewhere between 0 and -5.
>>> Has anyone encountered a digital pot that can either take a 10v supply,
>>> or has level shifters on the digital lines? I think I might be able to
>>> use a CD4052 with discrete resistors, but then it's a 16 pin chip I have
>>> to put on the board.
>>>
>>> Any ideas?
>>>
>> I assume the digital lines are 0->+5 V.
>
> If he is designing the whole stuff, you may assume digital lines are 0
> -5V (if it's a clever designer) so he don't need any level shifter.
>
> Vasle
>