[oopic] Re: Digital Potentiometers

I've never tried this chips, but they look kind of interesting (I have no affiliation with
Maxim):

http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2676

The DS1267 has two 256-position potentiometers, with wiper positions each set by stored
8-bit values. The DS1267 communicates through a 3-wire serial port interface that drives
an internal control logic unit. Multiple DS1267s can be linked or daisy-chained for control
by a single processor.

Digital potentiometers improve upon mechanical devices with processor control and
programmability, greater reliability and accuracy, and packaging options that facilitate
automatic assembly. This digital potentiometer offers extremely low-power use and
reliable, accurate performance throughout the industrial temperature range.

The DS1267 is ideal for controlling the incoming signal levels in modems and for level
adjustment and control of RF and audio signals in cellular telephones. Digital
potentiometers are also used for battery charging and control circuitry, tuning and
calibration, offset trimming of operational amplifiers, gain control, and power supply
regulation.

Key Features Applications/Uses
Two 256-step (or 8-bit) digital potentiometers
Stacking configures device as one 512-step (or 9-bit) digital potentiometer
Wipers digitally set and read through serial port
Ultra low-power consumption, quiet, pumpless design
3-wire serial control interface
Operating ranges:
Single +5V or ±5V supplies
-40°C to +85°C

--- In oopic@yahoogroups.com, "rtstofer" <rstofer@...> wrote:
>
> --- In oopic@yahoogroups.com, carson hoyt <carr6565@> wrote:
> >
> > Thanks Richard that is exactly the kind of information I'm looking
> for. Another thing, I'm really looking to use multiple digipots, if I
> am making a lot of adjustments to the digipots is there going to be a
> lag time since the connection is I2C? Also can I control the pots
> individually on the I2C line if they are daisy chained together?
> > Concerning resolution: I'm going to be using these pots in an audio
> device. Should I be concerned about resolution. Right now I'm looking
> at pots with 1000+ resolution but these are kind of expensive and not
> available through my usual part supplier. I guess I'll just start
> small and work my way. I really appreciate the help.
> >
> > Carson
>
> There will be a way to have unique I2C addresses for quite a few
> devices. At least 8 in the case of the Maxim MAX5477..MMAX5479.
> Beyond that, things get complicated. Remember to divide the address
> by 2 when using the OOPic. Why? Well, the least significant bit is
> the R/W' bit and only the most significant 7 bits are address bits.
>
> The lag time for an OOPic will vary because the OOPic has to read the
> Basic code, interpret what needs to be done and then bit-bang the I2C
> message. Then it starts on the next 'pot. I would expect 5 mS
> between 'pot adjustments but that is just a wild guess. I have never
> timed it. It could be much more...
>
> If speed is your requirement, the OOPic isn't the way to get there.
> The 'pots can handle a 400 kHz clock rate and, if each command takes 3
> bytes, you would be looking at changing them at more than 10,000 times
> a second. Or all 8 in about a mS! But that would be with a more
> capable uC and coding in C.
>
> Richard
>

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