DAC60004: Clarification of device operation regarding maximum update across all four DACs.

Chris Woodyatt

Part Number: DAC60004
Other Parts Discussed in Thread: DAC8830, DAC8871, DAC81001

Could you clarify the overall update rate across all four DACs? Section 7.2 of the datasheet suggests successive DAC updates of 2.4 us, but it isn't clear what this means. I'd like to know how fast I can write new data to all four channels and then synchronously update them.
A quick calculation indicates that a single write would take 640 ns at 50 MHz, with a minimum of 25 ns SYNC high before the next write. Let's be a little conservative, so assume 680 ns times four writes, which would be 2.72 us. An asynchronous LDAC could occur 10 ns later at 2.73 us, giving an update rate of about 354 kHz. Is this the way the device works?

over 4 years ago

0 Akhilesh K over 4 years ago

TI__Mastermind 19086 points

Hi,

Your calculation is right in the sense that all timing related parameters. A single DAC update takes approximately 2.73uS (being conservative here also with max clock of 50MHz). But you forgot to add one key parameter to account for update rate. Thats the settling time.

For DAC6004, settling time typical is 5.8uS, you need to add this to your 2.73uS to arrive at the update rate of the DAC.

For more information, I am attaching a link where we talk about settling time and update rate in the Precision DAC Series.

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

Let me know if you have more questions regarding this

Regards,

0 Chris Woodyatt over 4 years ago in reply to Akhilesh K

Prodigy 130 points

AK,

thanks for the response. I've studied figures 44 and 45 in the datasheet which show the settiling time. Maybe next time the datasheet is updated you could include a cross-reference to those two figures from the timing section.

Are there any similar Texas products with settling times of around 2.5 us? Is there a single DAC with a 16 bit register and an external pin to allow synchronisation across multiple devices?

Cheers,

Chris

0 Akhilesh K over 4 years ago in reply to Chris Woodyatt

TI__Mastermind 19086 points

Hi Chris,

Point noted, will definitely add cross reference to settling time.

For now, if you are looking for 16bit DAC with less than 2.5uS, you can have a look at DAC81001, DAC8871 or DAC8830, these are unbuffered voltage output DAC's.

All DAC's have LDAC functionality which you can use to update the DAC's synchronously

Regards,

0 Chris Woodyatt over 4 years ago in reply to Akhilesh K

Prodigy 130 points

AK,

thanks for your responses. I will go and have a look at the devices that you've suggested.

Cheers,

Chris

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DAC60004: Clarification of device operation regarding maximum update across all four DACs.