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TPS61094: Output Noise at low output current (10uA to 200uA)

Mahmoud Gshash
Prodigy 40 points
Part Number: TPS61094
Other Parts Discussed in Thread: TLV7031, LM334, BQ25504, , TPS61299, TPS7A02, TPS7A03

Hi there,

I am working on design that uses TPS61094 to regulate the output of BQ25504 to 4.5V to remove the effect of MPPT. The TPS61094 is loaded with LM334 and the current is set to 10uA. The output of the TPS61094 is also used to as a supply to TLV7031 comparator. The noise on the comparator's supply is causing timing errors in my system. I would like to reduce the ouput noise from 50 mV P-P to less than 10 mV P-P and I have considered the following: 

- Adding an LDO (this will affect the overall effeciency of my system and increase my BOM cost)
- Adding a second stage output filter (Not sure how to go about this option)
- Adding a ferrite bead to reduce the high frequency noise

The System is powered by an RF-DC converter and maintaining high efficiency is important

Looking forward to hearing from you soon

Thanks,

Mahmoud

  • 0
    TI__Genius 12245 points

    Hi Mahmoud,

    You can try with our new device TPS61299, ultra low iq and low ripple Boost device. The ripple in light load is much smaller than TPS61094.

    Regards,

    Nathan

  • 0 in reply to Nathan Ding
    Prodigy 40 points

    Hi Nathan,
    Thanks for getting back to me in a timely manner. Although the TPS61299 does have a lower ripple it is about 5 to 8% less efficient at light load. Also, it does not seem to be in stock in any of the normal vendors. I looked at placing the TPS7A02 at the output, but it does not have a 4.5V option. I can do away with an extra 1uA of current for the the TPS7A02. If I set the output of the TPS61094 to 5V, would I be able to get 4.5V out the TPS7A02?

    Thanks,

    Mahmoud

  • 0 in reply to Mahmoud Gshash
    TI__Genius 12245 points

    Hi Mahmoun,

    According to the TPS7A02 d/s,  there is 4.5V option, but I am not very sure because I am not the expert for LDO devices. I loop LDO team to help with your questions.

    Regards,

    Nathan

  • 0 in reply to Nathan Ding
    TI__Mastermind 37005 points

    Hi Mahmoun,

    The challenge you have is that 4.5V is not a common output voltage for a regulator, which means you need an adjustable regulator in many cases.  We can create a 4.5V version of this LDO if the business case is strong enough, as it takes resources to create the updated die, qualify it, and release it.  Can you use an LDO that generates 5V output?  If so then the TPS7A03 is a good choice.  If you absolutely must have 4.5V then you'll need to accept a compromise in noise or quiescent current draw, or both. 

    Thanks,

    Stephen