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TPS7A7100: 0.9V VOUT LDO

Premsagar Kittur
Intellectual 255 points
Part Number: TPS7A7100
Other Parts Discussed in Thread: TPS7A90, TPS7A84A

Hello,

I am looking for an LDO with Min Vout = 0.8V to Max Vout = 1.2V. Vin is adjustable (always greater than 2V). Iload expected is about 100mA. It is for an application running at ~100MHz, so PSRR should be around 20-25dB at this frequency (not a strict requirement). We don't really care about the power consumption of the LDO, capped or capless LDO. 

Is TPS7A7100 the best match for our requirement or do you suggest anything else..??

Thanks

  • 0
    TI__Guru 55940 points
    Hi Premsagar,

    TPS7A90 sounds like it may be a better fit for your application as it has high PSRR, has an adjustable output that can achieve 0.8 V to 1.2 V, and is rated to 500 mA. Please note that at 100 MHz, the LDO contribution towards PSRR will be negligible as this frequency is outside of the bandwidth of the LDO. It is the output capacitor and any other external filtering (pi filters) which will provide PSRR at the system level for 100 MHz. TPS7A90 is a better fit for this as it does not have any practical upper limit to the output capacitance size. This allows for additional capacitance and pi filtering on the output of the LDO; whereas, the TPS7A7100 has a strict upper limit to the capacitance allowed on the output rail.

    Very Respectfully,
    Ryan
  • 0 in reply to Ryan Eslinger
    Intellectual 255 points

    Hello Ryan,

    Thanks for the quick reply. I did not notice the strict output cap limit in case of  TPS7A7100. 

    Thanks for the suggestion. We will go with TPS7A90. However, I have a question regarding TPS7A90. If there is no limit on the output cap, I believe its the dominant pole. So if I place more De-cap between the output of the LDO and my target chip, LDO will become slower. Is it right? (I believe the bandwidth of the LDO is <<100MHz)

  • 0 in reply to Premsagar Kittur
    TI__Guru 55940 points
    Hi Premsagar,

    You are correct that as more capacitance is placed on the output rail, the LDO response will become slower. Yes the bandwidth of an LDO is much less than 100 MHz.

    The following application report can help explain LDO control loop theory

    www.ti.com/.../snva167a.pdf

    Very Respectfully,
    Ryan
  • 0 in reply to Ryan Eslinger
    Intellectual 255 points

    Hi Ryan,

    Thank you very much for the support. We are from UCLA and will be using these chips for research purpose. What is the min quantity to order these chips? 

    Thanks,

    Premsagar 

  • 0 in reply to Premsagar Kittur
    TI__Guru 55940 points
    Hi Premsagar,

    The Sample & Buy tab of the product folder (direct link below) provides links to various distributor options. When you click the Order Now button, you will find the link to vendors as well as a link to the TI Store. The minimum quantity on the TI Store should 1 unit.

    www.ti.com/.../samplebuy

    Very Respectfully,
    Ryan
  • 0 in reply to Premsagar Kittur
    Intellectual 255 points
    Hello,

    I am looking for the same IC (TPS7A7100), but with digitally programmable output. I mean, we want to control the output voltage using digital signal from FPGA. If the option (digitally programmable output) is not available for this IC, then can you suggest something else.



    I tried searching on your website and found TPS7A84A which can be programmed by either grounding the programming pins or making it open. We cannot control this with the help of FPGA.

    Your help will be appreciated here.

    Thank you
  • 0 in reply to Premsagar Kittur
    TI__Guru 55940 points
    Hi Premsagar,

    It appears that you posted the same question on two threads. As such, we are considering this thread closed and will continue supporting you on your thread located here:

    e2e.ti.com/.../713157

    Very Respectfully,
    Ryan