DAC7811: About DAC7811 circuit

tsuyoshi tokumoto

Part Number: DAC7811
Other Parts Discussed in Thread: DAC8811

Hi team,

I am considering replacing another maker's multiplying DAC with DAC7811
at my customer.
Please see the attached file.

DAC_circuit.xlsx
I think that DAC7811 is usable and the Cf can be used not only for phase
compensation but also for LPF by increasing Cf value.

Is my understanding correct?

If you have any concerns about that please let me know.

Sincerely,
Tsuyoshi Tokumoto

over 5 years ago

0 Uttam Sahu over 5 years ago

TI__Genius 14220 points

Hi Tsuyoshi-san,

Thank you for your query. I don't see any problem in using Cf for creating a first-order LPF. However, if you need a proper BW limit, I would recommend using another LPF stage after the transimpedance amplifier.

There is a previous E2E post that talks about the multiplying bandwidth and a simplified model of the MDAC. You can use that to replicate the filter behavior by changing Cf.

e2e.ti.com/.../671207

Hope that answers your question.

Regards,
Uttam Sahu
Applications Engineer, Precision DACs

0 tsuyoshi tokumoto over 5 years ago in reply to Uttam Sahu

Expert 2630 points

Hi Uttam-san,

Thank you very much for your prompt reply.
I will use your advice as a reference from now on.

Thank you and best regards,
Tsuyoshi Tokumoto

0 tsuyoshi tokumoto over 5 years ago in reply to Uttam Sahu

Expert 2630 points

Hi Uttam-san,

　Please let me ask you an additional question.

　My customer is considering using the DAC7811 now.
　In his current design situation, the DAC 7811 needs to be controlled by a serial
　interface with 24-bit width.
　I believe that the DAC7811 will be controlled correctly by placing valid data
　in the lower 16bits.
　　*Please see the attached file.

Dac7811_input.xlsx
Is my understanding correct?

Thank you and best regards,
Tsuyoshi Tokumoto

0 Uttam Sahu over 5 years ago in reply to tsuyoshi tokumoto

TI__Genius 14220 points

Hi Tsuyoshi-san,

I think this scheme should work but I need to test it on the EVM before I can confirm. I will get back by next week.

Regards,
Uttam

0 tsuyoshi tokumoto over 5 years ago in reply to Uttam Sahu

Expert 2630 points

Hi Uttam-san,

Thank you very much for your prompt reply.
I really appreciate your cooperation!

I look forward to your answer.

Thank you and best regards,
Tsuyoshi Tokumoto

0 tsuyoshi tokumoto over 5 years ago in reply to Uttam Sahu

Expert 2630 points

Hi Uttam-san,

　I would appreciate it if you could share the test result on the EVM with me.
　I apologize for rushing you, but I would like to reply to my customer
　about this question by the end of the week.

Thank you and best regards,
Tsuyoshi Tokumoto

0 Uttam Sahu over 5 years ago in reply to tsuyoshi tokumoto

TI__Genius 14220 points

Tsuyoshi-san,

I will upload my findings tomorrow.

Regards,
Uttam

0 tsuyoshi tokumoto over 5 years ago in reply to Uttam Sahu

Expert 2630 points

Hi Uttam-san,

I appreciate your understanding and cooperation.
I look forward to your findings.

Thank you and best regards,
Tsuyoshi Tokumoto

0 Uttam Sahu over 5 years ago in reply to tsuyoshi tokumoto

TI__Genius 14220 points

Hi Tsuyoshi-san,

I tested it on the EVM. It works. In a 24-bit SPI frame, the DAC8811 takes the last 16 bits.

Hope that answers your question.

Regards,
Uttam

0 tsuyoshi tokumoto over 5 years ago in reply to Uttam Sahu

Expert 2630 points

Hi Uttam-san,

Thank you for the good news!
I shared your answer with my customer.
I appreciate your cooperation

Thank you and best regards,
Tsuyoshi Tokumoto

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DAC7811: About DAC7811 circuit