How is this DAC output design called - Page 1
Forum section: electronics / projects

author: Zom-B
author_rank: Regular Contributor
timestamp: January 08, 2017, 01:21:05 pm
content: How is this DAC output configuration called?how can I search for DACs with this specific output configuration this on E14/RS/M/etc shops?The part I found this output configuration in (apparently this part is being deprecated):https://www.maximintegrated.com/en/products/analog/data-converters/digital-to-analog-converters/MAX5152.html(background: I want to make a PSU similar to Dave's µSupply, but save on some external op-amps.)

author: timb
author_rank: Super Contributor
timestamp: January 08, 2017, 03:16:27 pm
content: That image doesn't really give enough information for us to tell you specifically what type of DAC it is, however it appears to be a dual output, buffered voltage DAC. At 16-bits it's most likely using an R2R ladder for each DAC.Take a look at Linear Tech, Analog Devices and Texas Instruments. They all make 16-bit DACs and have parametric search pages that will let you filter by Current and Buffered/Unbuffered Voltage DACs.That said, 16-bit is way overkill for a basic bench power supply, unless you need uA/uV level control of the output. (In which case you'd be better off with a current output DAC and a separate precision Op-amp!) 12-bits should do fine for you, 14-bits at the max.

author: Zom-B
author_rank: Regular Contributor
timestamp: January 10, 2017, 06:53:11 pm
content: What I'm referring to is the internal Op-amp before the output pins.When I search for regular current and buffered voltage outputs, I get parts with an output stage that does not include an op-amp, or one that has a fixed / variable amplification, but without exposed feedback pins.I checked four mfrs for 12-bit 2ch buffered voltage DACs, and finally found exactly one: MAX5156... which is also phased out.BTW, something likeMAX5154with resistors between the output and FB lines is unacceptable, because I'd need external op-amps to shift the signal, defeating the purpose of internal op-amps.

author: ajb
author_rank: Super Contributor
timestamp: January 10, 2017, 08:25:23 pm
content: That's a neat feature, but there's nothing you could do with that part that you can't do with a couple of external op-amps. In fact there's a lot more you can do with fully independent op amps, and you have lots of choices in MSOP8 and such packages that won't take up too much board space.

author: timb
author_rank: Super Contributor
timestamp: January 11, 2017, 02:39:48 am
content: All buffered output DACs essentially include an internal op-amp after the DAC; that's why they're called buffered! Most don't break out the inverting pin and instead have it connected internally at the output.Non-buffered voltage DACs essentially give you the weak output direct from the resistor ladder. A current DAC is similar, but it generally also provides access to additional parts of the R2R ladder (the Rf/Rg pins) which are used with an external op-amp hooked up as a current to voltage amplifier (most of the time current output DACs are really used to generate a voltage, it's just done outside the part for a variety of reasons, including precision).Edit: If you want the best performance, get a current DAC and hook a high quality, low drift op-amp as stated above. That will essentially give you what you want.

author: bson
author_rank: Unknown
timestamp: January 11, 2017, 09:38:04 pm
content: They're called sense pins. Sometimes they have resistors, at other times not. See e.g.http://www.ti.com/product/dac7632