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3.3V LDO regulator with adjustable UVLO

Alex Blah
Prodigy 40 points
Other Parts Discussed in Thread: TPS61200, TPS709, TPS3808

I am looking for a 3.3V LDO regulator to use with my lithium ion battery, and I want it to have an adjustable UVLO that disables the regulator when the battery voltage is low.  So far I can only find a 3.3V buck/boost regulator like TPS61200 that has this feature.  Is there an inherent reason for this? Or does such a part exist?

  • 0
    TI__Expert 6965 points
    Hi Alex,
    What you will want to do is to get a 3V3 LDO that has an enable pin and then monitor the battery voltage with a supervisor. The supervisor will tell you when the voltage is low and can either enable or disable the LDO.
    Best Regards,Mark
  • 0 in reply to Mark Sellers
    Prodigy 40 points
    Is a "supervisor" the same thing as a low voltage comparator? ...I wonder why there are no LDOs with this built-in feature...
  • 0 in reply to Alex Blah
    Prodigy 40 points
    I just found this TI part (TPS76633): www.ti.com/.../tps76601.pdf that says it has a power good output that indicates if the output voltage is a small percentage below its regulated value. Is there a problem with tying the power good output to enable in order to eliminate the need for an external supervisor?
  • 0 in reply to Mark Sellers
    Prodigy 40 points
    I just found this TI part (TPS76633): www.ti.com/.../tps76601.pdf that says it has a power good output that indicates if the output voltage is a small percentage below its regulated value. Is there a problem with tying the power good output to enable in order to eliminate the need for an external supervisor?
  • 0 in reply to Alex Blah
    TI__Expert 6965 points

    Hi Alex,

     

    What you have described will not work due to the fact that the power good indicator is going to take the signal low when the battery droops. Thus, if you directly hook the power good signal to the enable, when the power is good the LDO will never turn on. I would recommend using a supervisor, such as, the TPS3808 for monitoring the battery voltage. Then connect the reset pin of the supervisor to the enable pin of an LDO such as the TPS709, where the enable pin low shuts down the device, while the enable pin high turns it on.

     

    Regards,

    Mark