Lowest Vref for DAC 8564

One addtional Information

it is +/-150 mV

Thanks & Regards

Aravind

Aravind,

There is no lower limit on the smallest reference input voltage the device can use. It's worth pointing out, though, that some of the device specifications may no longer hold true with exceptionally small reference voltages, though. This behavior is not characterized so I cannot predict exactly how performance will degrade.

I would recommend using a larger reference voltage that is coherent with the electrical characteristics table and then use an external solution to attenuate the voltage to the range you are interested in.

Hi Kevin,

Thanks for the information.

One question.Won't I be loosing out on the step size resolution If I go for a higher reference.

What about going for a higher resolution DAC. But I am not finding a quad channel higher resolution DAC.Is there a possibility of sending all the channel data sequentially and demuxing the analog out put.

For example If I go for  9881(18 bit),I could give 1.2V reference for getting the needed step size,but how can I support 4 channels.Each of my channel is 32 KSPS and I want the output to be updated as simultaneous as possible.Also I couldn't find the maximum update rate for 9881 from the data sheet.

Thanks & Regards

Aravind

Aravind Ravikumar said:

One question.Won't I be loosing out on the step size resolution If I go for a higher reference.

If you apply attenuation externally then both the full-scale output and the LSB weight will be attenuated. Like I mentioned previously, using an exceptionally small reference voltage is potentially going to impact performance of the DAC. Additionally, though, very low voltage reference solutions are not very common. You're much more likely to find a 2.5V, 4.098V, or 5V reference. 

LSB weight for a 16-bit DAC with 2.5V reference is ~38.15uV. If you were to apply ~1/8.5 attenuation you'd get the step size you were hoping for.

Aravind Ravikumar said:

What about going for a higher resolution DAC. But I am not finding a quad channel higher resolution DAC.Is there a possibility of sending all the channel data sequentially and demuxing the analog out put.

I'm not exactly sure what you mean.

There are a few devices in our portfolio that have a variety of "software LDAC" commands that can latch channels individually, in pairs, or all of them simultaneously. DAC8564 is an example.

Aravind Ravikumar said:

Also I couldn't find the maximum update rate for 9881 from the data sheet.

Maximum update rate is usually limited by settling time since a fully settled output is usually desired. If you do not require fully settled outputs for each update or if you're moving across a smaller code transition than the settling time specification was characterized with, you can push the device to it's digital bus limits.

Hi Kevin,

Thanks for clarifying.As you suggested I will go for higher Vref and scale down ate the output.

Few  questions on the performance of DAC 8564:

What is the ENOB for DAC 8564 and at what bandwidth

What is the TUE

What I meant by higher resolution in previous post is: Was looking Quad channel 18,20, or 24 bit resolution DAC.I could see such higher resolution DACs,but all are single channel.(1280,9881 and two more) hence the question of giving all channels sequentially to DAC and separating it out on the analog side with a demuliplexer

Thanks & Regards

Aravind

Aravind Ravikumar said:

What is the ENOB for DAC 8564 and at what bandwidth

Precision DACs are designed for dc operation. While they may be successful in low to mid frequency ac applications, we do not provide specifications such as ENOB.

Aravind Ravikumar said:

What is the TUE

I wrote a blog post on Analog Wire about this. Check it out here.

Aravind Ravikumar said:

What I meant by higher resolution in previous post is: Was looking Quad channel 18,20, or 24 bit resolution DAC.I could see such higher resolution DACs,but all are single channel.(1280,9881 and two more) hence the question of giving all channels sequentially to DAC and separating it out on the analog side with a demuliplexer

I understand your query for a multichannel high-resolution DAC - these products do not exist in our portfolio. Usually applications that are interested in very high resolution DACs do not use multiple channels. What is your application that requires several high resolution channels?

My confusion lies in what you mean by "giving all channels sequentially to DAC and separating it out on the analog side with a demultixplexer." Maybe a diagram would help...

Thanks Kevin,

My application is something very similar to a high precision physiological signal simulator.Cost is also one constraint.hence looking for a quad channel DAC instead of four separate ones.

I was having a plan to use a  analog demux in the output of DAC to separate into four channel.Now I realize that it is difficult to get near simultaneous output with such an arrangement due to the update rate limit

Regards

Aravind 

Hi Kevin,

I have got a DAC 8564 evaluation board.I am trying to connect it to MMB0 board and use the DXP software to test the DAC.

1. Is it possible to do that.
2. What jumper settings need to be taken care in the DAC board and the evaluation board.

The DXP software is giving an error  "The VI is not executable. The full development version of Labview is required to fix the errors" 

But I am able to use  the Labview software provide along with ADS1298 in the same PC(Windows 8) and the same MMB0 board.Any suggestions on how to resolve this error?

Thanks & Regards

Aravind

Aravind,

Sorry for the delayed response - this slipped through during the US Holidays.

If you're still troubleshooting this issue, the best place to start would be a screen capture of the PC's Device Manager when the device is plugged in and before DXP has been loaded. Then, an additional screenshot of the PC's Device Manager after DXP has been loaded.

I haven't seen this particular error before, and Windows 8 isn't a platform that we officially support for either the ADS1298 or DXP. That said, I have had success installing DXP on a touchscreen Windows 8 PC but not without some massaging.

If you have access to a Windows XP or Windows 7 PC that may be the easiest way to get your evaluation up and running quickly.

Thanks Kevin,

Infact I have moved to Windows7 and DXP is working fine.There was an issue in the automatic downloading of XML file.So I manually downloaded from the link below and copied to device's folder

ftp://ftp.ti.com/pub/data_acquisition/DXP/Devices/DAC8564.xml

Regards

Aravind