DAC - Page 1
Forum section: electronics / beginners

author: arivel
author_rank: Regular Contributor
timestamp: August 23, 2020, 09:18:24 am
content: Hello .is there an integrated DAC with the following characteristics? :high output current. minimum 30 mA.parallel inputs.without clock.minimum 8 bits

author: tggzzz
author_rank: Super Contributor
timestamp: August 23, 2020, 09:42:09 am
content: Use DigiKey's search facility.Decide whether you want a naked DAC or an evaluation board.You may need to add your own buffer to obtain a higher current output.Apart from that, knowing yourproblem/goalrather than yoursolutioncan help people give you better answers; seethisfor an example why!

author: Doctorandus_P
author_rank: Super Contributor
timestamp: August 24, 2020, 12:01:11 am
content: A 30mA output current is likely to influence the output voltage accuracy.It may also add deviations due to (slow) heating of the IC.So even if you stay within "absolute maximum ratings" it's still probably not the best solution.What's wrong with adding an opamp or 2?

author: MarkF
author_rank: Super Contributor
timestamp: August 24, 2020, 01:45:11 am
content: There is the DAC08 with 8-bit parallel inputs but the output current is only 2mA.https://www.mouser.com/ProductDetail/Texas-Instruments/DAC0800LCM-NOPB?qs=7X5t%252BdzoRHB3UMLDAB6Vww%3D%3DA 10-bit parallel.https://www.mouser.com/ProductDetail/Maxim-Integrated/MX7530JN%2b?qs=wTZ%2FFzl837Z60rCeI015bQ%3D%3DNot all in one packages. You will probably need to have an op-amp to get your current level.

author: arivel
author_rank: Regular Contributor
timestamp: August 24, 2020, 03:08:42 pm
content: R-2R ?

author: MarkF
author_rank: Super Contributor
timestamp: August 24, 2020, 03:16:50 pm
content: Quote from: arivel on August 24, 2020, 03:08:42 pmYes. That is basically what is internal to the parts I linked.The advantage is that the parallel inputs are buffered so that each receives the same digital voltage.If you're not very particular of the step voltage, you could just use one of the R2R resistor ladder SIPs.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: August 24, 2020, 04:31:35 pm
content: R-2R won't work with high output current.Any loading of the output wil decrease lineairity.Building discrete R-2R networks is also not so straight forward.The best resistors you can buy for a reasonable price are 0.1% which would limit the DAC to about 10 bits.With standard 5% tolerance resistors you only get to 6 bits.

author: MarkF
author_rank: Super Contributor
timestamp: August 24, 2020, 05:13:56 pm
content: Quote from: Doctorandus_P on August 24, 2020, 04:31:35 pmA 2% tolerance R2R network in a SOIC package is not so bad...https://www.mouser.com/ProductDetail/Bourns/4816P-R2R-103LF?qs=ywolDd32d7%2FY0wPpCpCeWQ%3D%3DThey are about the same price as a parallel DAC. So why spin one yourself?Like you said though, the output needs buffering either way.

author: arivel
author_rank: Regular Contributor
timestamp: August 24, 2020, 07:16:06 pm
content: what if I use an operational amplifier with weighted resistances?I don't need very precise voltage steps.I went to see among the power amplifiers of TI and there are many, I don't know which one to choose, I focused on 2544

author: tooki
author_rank: Super Contributor
timestamp: August 24, 2020, 07:21:38 pm
content: As tggzzz already asked:What problem are you trying to solve?Answering that will save us and you time and frustration.

author: arivel
author_rank: Regular Contributor
timestamp: August 25, 2020, 03:50:15 pm
content: I try to understand if I can command the following attenuator:https://diyaudioprojects.com/Solid/DIY-Lightspeed-Passive-Attenuator/using the circuit I posted here:https://www.eevblog.com/forum/beginners/supply/msg3133082/#msg3133082at number six.the idea is to bring the outputs of the 40193s to the DAC and then the output ofthe latter pilots the LDRs.in my case the 100K potentiometer is eliminated

author: ledtester
author_rank: Super Contributor
timestamp: August 26, 2020, 03:58:25 am
content: You should build the circuit with a pot and measure what kind of current you really need for the various audio levels you want to achieve. There's a lot of tuning involved in that design, and it seems a lot of that depends on the parts you actually have given the variation that the author mentions.It is very likely you don't need the DAC to source 30 mA... on the last page of the datasheet for the NSL-32R2 it is clear that practically all of the resistance range is achieved by 0 to 5 mA of current through the LED.https://lunainc.com/wp-content/uploads/2016/06/NSL-32SR2.pdf(As an aside... I would suggest you learn to use a microcontroller such as the Arduino. It will greatly simplify your design by replacing all of your digital logic ICs.)