Author Topic: Digital input on DAC? (datasheet confusion MP7531JN)  (Read 1430 times)

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Offline SArepairman

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Digital input on DAC? (datasheet confusion MP7531JN)
« on: July 15, 2013, 08:01:55 pm »
http://www.datasheetarchive.com/MP7531JN-datasheet.html

I am testing this DAC and It says on the first page that Logical 1 at digital input steers current to Iout1.

I set the dac up with a IV converter op-amp using Rref and the Iout1 works fine, but I have no idea how to activate Iout2.
What do they mean by digital input? When I leave it as it is and measure Iout2 it goes from 12-14 volts.... did they forget to add a pin?   :wtf:

I thought it might have meant that Floating-Ground = output 2 and vdd-ground = output one but I tried it and it does not work.

I also tried grounding and vdding Iout1 and it does not change Iout2, where the steps change it from 12 to 14
« Last Edit: July 15, 2013, 08:07:11 pm by SArepairman »
 

Online PA0PBZ

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Re: Digital input on DAC? (datasheet confusion MP7531JN)
« Reply #1 on: July 15, 2013, 10:58:59 pm »
Another multiplying DAC: http://www.ti.com/lit/ds/slas061d/slas061d.pdf

Strat reading from page 5 how these things work, you are supposed to use both outputs.

About the "Logical 1 at digital input steers current to Iout1" see the diagram on the first page of the document you linked, the inputs control the switches.

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Offline SArepairman

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Re: Digital input on DAC? (datasheet confusion MP7531JN)
« Reply #2 on: July 16, 2013, 03:25:09 am »
I realized that in the schematic the second output is grounded so I don't think I will even bother to test it, I can't imagine they need to use an abnormal dac for generating a sweep wave form.

There is just a buffered voltage reference for vref and a IV converter+Pi RC filter for Iout1 and Iout2 is grounded, I don't think its doing anything odd.

I guess the multiplication feature is kind of odd ball... I don't believe its used here.
Maybe the company bought 50,000 of them and they decided to use it instead of a traditional dac?
« Last Edit: July 16, 2013, 03:42:28 am by SArepairman »
 

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Re: Digital input on DAC? (datasheet confusion MP7531JN)
« Reply #3 on: July 16, 2013, 04:19:49 am »
I had a broken MP7528 in my Marconi 2022 signal generator, which was there to tune the output notch filter. I suddenly noticed a lot of spurious in the signal and it turned out to be this DAC.
That one is a dual multiplying 8 bit dac, where the second half is used for jitter control. I never found out if they are using the multiplying function in there, but after replacing the DAC everything was fine again.
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