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DAC11001A: DAC11001A internal resistor matching, REFP, REFN capacitors, reference buffer op amp selection

user4972853
Prodigy 30 points
Part Number: DAC11001A
Other Parts Discussed in Thread: OPA189, TINA-TI, OPA192, OPA827

Hey everyone,

For an SMU-like device that requires good DC precision and fast settling, I'm evaluating the DAC11001A from TI. I have a few questions after going through the datasheet:

1. For my application, I would like to use the built-in resistors (available through pins ROFS, RCM and RFB) to generate the negative reference voltage. What is the matching ratio of these internal resistors (typical, maximal)? Along the same lines, how well matched are they in terms of temperature drift?

2. The datasheet states for the capacitors in the feedback loop of the reference buffers, that "the values of C1 and C2 depend on the stability criteria of the reference buffers when driving the reference inputs of DACx1001. The values are obtained through simulation." How should I simulate this, e.g., using TINA-TI for the OPA192 and OPA189 op amps? Or can you perhaps recommend values for C1, C2 for these two op amps?

2. As they are already used elsewhere in the design and have excellent DC specifications, the OPA189 or OPA192 would be preferred candidates to use for the reference buffers. I noticed the OPA189 is mentioned explicitly in the datasheet. Would the OPA192 also work in this position, or would it adversely affect the performance of the DAC (apart from the slightly higher output voltage offset)?

Best regards,

Jacques

  • 0
    TI__Mastermind 18546 points

    Hi,

    First of all, thanks for choosing DAC11001A . Its well suited for your application

    For your questions, 

    1. Absolute tolerance of the resistors can vary, but their matching is very tight, I will get the exact numbers from my design team

    2. Since OPA189 and OPA192 have comparable bandwidth and open loop output impedance, the recommendation for OPA189 should still hold good for OPA192.Neverthless I will simulate the same and get back to you ASAP

    3. We characterize our device with OPA827 as the output buffer and reference buffers. Choice of this really depends on the application. For your application I believe OPA189 is good choice

    Regards,

    AK

  • 0 in reply to Akhilesh K
    Prodigy 30 points

    Dear Akhilesh,

    Thanks for your answers so far. I look forward to the rest of the information.

    Best regards,

    Jacques

  • +1 in reply to user4972853
    TI__Mastermind 18546 points

    Hi,

    Sorry for late reply.

    You can assume that the resistor matching will be about 12.5bit (1-sigma) which is about 0.017%.  The actual mismatch could be lower.

    The temperature drift of the resistors is typically about 3ppm/C and worst case +/-25ppm/C.

    The temperature drift of the resistor mismatch is 0.1ppm/C (typ) and 0.5ppm/C (max)

    Regards,

    AK