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Favorite multi-channel DAC with serial interface?

Discussion in 'Electronic Design' started by Joerg, Aug 20, 2006.

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  1. Joerg

    Joerg Guest

    Hello Folks,

    What is your favorite DAC if you have to set a dozen or more DC voltages
    via a serial bus? Of course, ideally it should be cheap, multi-sourced,
    available from a couple of big suppliers (ahem, no vaporware...). 8-10
    bits ok, or more. External ref preferred unless the internal one is
    really good. Speed does not matter at all.

    The bus type is still open. Guess I2C is favored for non-star
    architectures but in the end it doesn't matter much as long as the
    protocol is easy on the SW guys.
     
  2. Nico Coesel

    Nico Coesel Guest

    Multi sourced? That's a tough one. I doubt you'll find even one 8
    output DAC.
    Personally, I like the AD5318 from Analog. It can use 2 references.
     
  3. linnix

    linnix Guest

    I would do it with A2D and PWM adjusted LM317. We need the D2A (317)
    for our A2D sensors, but there's no reason why you can't use the A2D
    for your D2A. A micro with A2D can do I2C, 232 and/or USB (or some
    other 3 letters words). You can set external analog reference with the
    micro. Most micro can do 10 bits with internal ref with good result.
     
  4. PeteS

    PeteS Guest

    Hi Joerg

    Most A-Ds max out (standard ones, anyway) at 8 channels. For a low cost
    easy to use part, I tend to use the National ADC08* series. There is a
    16 channel device, but it's parallel and more expensive.

    If you can live with 2 devices I'd use the ADC088S022. $1.31 / 500
    budgetary. Separate reference input for the converter. The 8 bit
    device is about $5 in the same qtys. (I have 2 of these in a current
    design for system voltage monitoring).

    I seem to recall a number of others make the ADC08* series, but I might
    be wrong. On the other hand, I have not had problems getting the parts
    from National.

    SPI style interface on this part - uses a CS, so providing you can
    generate separate CS outputs from the controller, you can have as many
    as you like.

    Cheers

    PeteS
     
  5. PeteS

    PeteS Guest

    That should have read:

    'The 16 channel device is about $5. The ADC088S022 is 8 bit, slow but
    it works.SAR style, so if there's noise (which I doubt from your
    description) you'd need some extra filtering. This thing is as old as
    the hills and it's still going strong.

    Cheers

    PeteS
     
  6. Joerg

    Joerg Guest

    Hello Nico,
    Well, there are octal DACs with a serial port, for example the TLC5628
    from TI. Around $2.50. However, since I rarely need such parts I don't
    know whether it is or may become a mainstream device.
     
  7. Joerg

    Joerg Guest

    Hello Pete,
    Thanks. That info might come in handy for a future design but this time
    I need a DAC ;-)

    I2C might be better but I could certainly make SPI work here. I'd just
    have to beg some more port pins for enough CS lines off the digital
    folks. Maybe a box of chocolates would help in the "convincing process".
    But then again a dozen or so devices would only need three CS bits.
     
  8. PeteS

    PeteS Guest

    LOL

    That'll teach me to read newsgroups and watch TV at the same time

    That said, there isn't much of a choice for multiple DACs. given my
    preference in suppliers and the fact you aren't looking for 'DSP
    quality' outputs, I'd take a TI device. I used the TLV5608 a little
    while ago and it was nice because of the separate digital and analog
    supplies.

    http://focus.ti.com/docs/prod/folders/print/tlv5608.html

    Just under $5 / 1k qtys

    Cheers

    PeteS
     
  9. Joerg

    Joerg Guest

    Hello Pete,
    Well, if the ball game was good then it was worth it. We are TV-deprived
    but happy with it. Only a dozen channels and half in Spanish, one 25" TV
    inside and a 13 incher on the deck, that's it.

    That looks like a great part and allows external ref which is good. It
    seems to be over $5 on the market right now but in this project that
    isn't a big issue (that's kind of nice for a change).

    I2C would be nicer because I could hang all kinds of other feedback
    stuff on it. But I feel uneasy designing one in from a EU company. Got
    burned too many times by botched delivery attempts.
     
  10. Jim Thompson

    Jim Thompson Guest

    [snip]

    We're also TV-deprived... only seven sets ;-)

    ...Jim Thompson
     

  11. Me too, and I've already given away three more. Two get turned on
    once in a while, and the others aren't even plugged in.


    Oh, yeah, I also have one of the first Motorola Quasar "Works in a
    Drawer" solid state color TVs made in the mid '60s and it still works.
    That makes eight.


    --
    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida
     
  12. Joerg

    Joerg Guest

    Hello Michael,
    Brings up a point discussed a while ago where someone said something
    about new TVs except for very small ones being required to contain a
    digital tuner. Well, a few weeks ago at Costco I looked. The label for a
    20" set explicitly said analog tuner, a 24" set did not mention a
    digital tuner (while all the really big ones did). So, is digital TV
    sliding?
     
  13. Nitro

    Nitro Guest

    Hi,

    I did not see it mentioned,
    We have had good luck with the Linear LTC2600 8-channel 16 bit SPI interface
    DAC, 2.5 to 5.5 with rail to rail drive. External ref or use VCC. (external
    ref is the max vout and must be <= VCC) They also have an 8 and 10 bit pin
    compatable version but we have been using the 16 bit version. They are on
    the pricy side.
     
  14. Perhaps the LTC1665 8x8 @3.55$, or the LTC2620 8x12 @9.00$,
    they are single source though.

    Rene
     
  15. Nico Coesel

    Nico Coesel Guest

    Most manufacturors have octal DACs, but all of them are
    pin-incompatible despite the almost identical functionality. Work to
    do be done for Jedec.
     
  16. The LTC1665 8x8 for 3.55$ and the LTC2620 8x12 for 9.00$ come to my
    mind. Both single sourced though.

    Rene
     
  17. Joerg

    Joerg Guest

    Hello Nico,
    Yes, and they are mostly SPI so maybe I2C isn't the thing anymore to
    push in cases like this. Even though it would be perfect here. I was
    taken aback by the fact that Philips doesn't offer much as the parent of
    I2C. Could only find some audio converters.

    Waiting for JEDEC to fix the turf wrestling would be like waiting for an
    EDIF standard for schematics which IMHO is never going to happen. So,
    maybe each device needs 2-3 positions with only one being occupied,
    depending on which DAC is purchased.
     
  18. Joerg

    Joerg Guest

    Hello Nitro,
    Thanks for the hint. Looks like I'll go with an 8-ch SPI version because
    they seem quite prevalent. The LTC part shows no stock at Digikey which
    raises a bit of a flag here. But the TLV5608 from TI is in stock.

    Take a look at the AD5391: A whopping 16 channels.
     
  19. Joerg

    Joerg Guest

    Hello Rene,

    Thanks. They look good. Although the numbers in stock at Digikey are
    really low which in the US is often considered the "popularity barometer".
     


  20. I hope so. I don't plan on buying one.


    --
    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida
     
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