DAC like MCP4726, but with more bits of resolution? - Page 1
Forum section: electronics / projects

author: TERRA Operative
author_rank: Super Contributor
timestamp: July 29, 2023, 06:25:43 am
content: I'm looking for a DAC like the MCP4726 but with more bits of resolution.I need to create an adjustable DC voltage from 15.800V down to 458.69uV and the 12 bits of the MCP4276 isn't quite enough.Is there any DAC that I can control with an Arduino/etc that accepts an external vref with more than 12 bits of resolution?

author: Kleinstein
author_rank: Super Contributor
timestamp: July 29, 2023, 06:39:31 am
content: There are a few 14 and 16 bit string DACs from Ti and likely others. The DAC8531 would be such an example - not sure if currently available and if there is a more afordable alternative.

author: dobsonr741
author_rank: Frequent Contributor
timestamp: July 29, 2023, 07:38:47 am
content: You’ll find hundreds of DACs with >12bit resolution if you use the distributors or the manufacturers parametric search.

author: Kanbus
author_rank: Contributor
timestamp: July 30, 2023, 12:53:13 am
content: AD5662Easy to use. A bit pricey though.https://github.com/avandalen/avdweb_DAC16

author: TERRA Operative
author_rank: Super Contributor
timestamp: July 30, 2023, 01:33:57 am
content: Cool thanks!Is there a 20-bit DAC that is common to use with Arduino etc? (As in I don't have to start from scratch with libraries etc)?So far I'm looking at the MAX5719.

author: PCB.Wiz
author_rank: Super Contributor
timestamp: July 30, 2023, 02:25:30 am
content: There is also parts like DAC1220How fast does this DAC need to be ? 'adjustable DC voltage' suggest trimming / set points ?For slow DACs, another popular method is merged PWMs, where you create multiple PWM outputs of 8~12 bits and use 2^N weighted resistors to merge them.

author: TERRA Operative
author_rank: Super Contributor
timestamp: July 30, 2023, 04:45:15 pm
content: It will be used for setting precise DC voltages, from a few hundred nV to 15.8V

author: voltsandjolts
author_rank: Unknown
timestamp: July 30, 2023, 05:00:26 pm
content: Quote from: PCB.Wiz on July 30, 2023, 02:25:30 amhttps://www.edn.com/combine-two-8-bit-outputs-to-make-one-16-bit-dac/

author: PCB.Wiz
author_rank: Super Contributor
timestamp: July 31, 2023, 01:16:37 am
content: Quote from: voltsandjolts on July 30, 2023, 05:00:26 pmThat's a good reference, I also found this update, around improved step response, tho here they target an 8-bit settle / ripple as the benchmark.https://www.ednasia.com/cancel-pwm-dac-ripple-with-analog-subtraction-revisited/

author: Kleinstein
author_rank: Super Contributor
timestamp: July 31, 2023, 07:01:53 am
content: The PWM ripple compensation makes the filter a 2nd order filter. It can still be worth it as it is a relatively simple way to build a 2nd order filter, but no magic.For combining 2 PWM channels for extra high resolution it helps if the fine part is really only a small fraction, as the resistor (and switch resistance) accuracy limits the useful resolution for the fine part to some 5-8 bits. So for 16 bit total one would not use 8 + 8 bits with a 1:258 resistor ratio, but more like 12+4 bits.

author: PCB.Wiz
author_rank: Super Contributor
timestamp: July 31, 2023, 07:38:35 am
content: Quote from: Kleinstein on July 31, 2023, 07:01:53 amI checked that on Spice, and you are correct in one part of the curve : the ultimate ripple attenuation is very similar - a few % different at ~30uV in my spice run.However, the rise time is quite different, as the plot shows (red trace is second order filter, brown trace is ripple cancel from 2023 edn )951us improved to 260us