DAC with low settling time

Ahamed Faize

Other Parts Discussed in Thread: DAC7760, DAC8760, DAC80502, DAC8832, DAC60502, DAC7750

We are searching for the DAC with below specifications,

Settling time : <=10 uS
Update Rate : >= 100 KHz
Resolution : >=12 Bit
No. of Channels : 2 (1 for current output & 1 for Voltage output)
Current Output : 4 to 20mA
Voltage Output : 0 to 10V
Digital Interface : SPI or I2C (SPI is preferred)

But we couldn't find any parts with these specifications in TI site. We want to know whether any of your ICs supports above specs.

over 5 years ago

0 Paul_Frost over 5 years ago

TI__Guru 56883 points

Hi Ahamed,

The closest we have to that is the DAC8760/DAC7760. Though you might struggle to achieve that sample rate as the settling time is a bit longer than 10µs. Otherwise, this device satisfies your requirements.

If settling and update rate are more critical, then you might have to look using a voltage output DAC and then implement your own voltage-to-current conversion discretely.

You could consider our unbuffered devices, like the DAC8832, or the buffered devices like the DAC80502.

Thanks,

Paul

0 Ahamed Faize over 5 years ago in reply to Paul_Frost

Intellectual 270 points

Hi Paul,

Thanks for the quick response. I will check these and come back soon.

Regards,

Faize

0 Ahamed Faize over 5 years ago in reply to Ahamed Faize

Intellectual 270 points

Hi Paul,

We have analysed your suggestions. But the parts DAC8760/DAC7760 are having only one channel. But our system needs 2 channel. One is dedicated for Voltage output & other one is dedicated for current output.

Awaiting for your further suggestions.

Stay safe!!

Regards

Ahamed Faize

0 Paul_Frost over 5 years ago in reply to Ahamed Faize

TI__Guru 56883 points

Hi Ahamed,

You will need to implement a two-chip solution either:

1. 2 channel DAC (DAC60502) + V/I output stage op-amp

2. a DAC7760 and DAC7750

0 Ahamed Faize over 5 years ago in reply to Paul_Frost

Intellectual 270 points

Hi Paul,

Thanks for your suggestions. Now we are interested to go with the 2nd option as mentioned by you.

But we couldn't find the update rate in datasheets. If you have any info on update rate, it will be really helpful for us to go with this option.

Thanks,

Faize

0 Akhilesh K over 5 years ago in reply to Ahamed Faize

TI__Mastermind 19136 points

Hi Faize,

As per suggestion I believe you are going to use DAC7760 for voltage output and DAC7750 for current right?

For DAC7760, your update rate will be predominantly determined by output voltage settling time, if you are looking for full step say from 0V to 5V or 0 to 10V its 13us and 22us respectively. Add to this your SPI timings, say 24SCLKs per transaction, you are looking at approx. 22us + 24*60ns (assuming max SPI, 16MHz)

In a similar way you can calculate for DAC7750 as well. Most of the time your settling time will be biggest factor with which you can update your DAC.

If you are looking at small step change, SPI transactions will be biggest contributor. We have precision DAC series video, which explains these bit more. Have a look at these in the below link

https://training.ti.com/lessons-precision-dacs-settling-time-vs-update-rate#:~:text=Settling%20time%20in%20a%20DAC,to%20enter%20the%20slew%20region.

Regards,

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DAC with low settling time