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TPS610985: Adding uPWR enable logic

Jack Gratteau25
Prodigy 40 points
Part Number: TPS610985
Other Parts Discussed in Thread: TPS61097A-33

I am currenly using the high efficiency converter in a uPwr application operating from a 1.5V battery. I need to be able to shut down the input power, or enable the input power when needed. My application is now moving from 10K-100K volumes to 100K-1M unit volumes. Similar circuits that exist for OMAP and related PMIC controllers, it would be useful if a version that implemented a high-side switch and enable logic combined with the TPS61 series converters existed. It takes a fair bit of discrete transistor logic to run in 0.7V-2V domain (a PMOS high side sw to start, a NMOS source follower in parallel and glue, draws 0.1uA in shutdown, 5uA during operation). Love to hear from a PMIC product manager to discuss.

Thanks

Jack Gratteau

Principal Engineer

Perceptimed Inc

  • 0
    TI__Mastermind 46905 points

    Hi Jack,

    the TPS610985 does have a switcher, are you asking to reduce the power loss the switcher?

    could you  have the block diagram and power sequence diagram to show to the idea? I will see if we can meet the request with current solution, or it is possible to build a new device.

  • 0 in reply to Jasper Li
    Prodigy 40 points

    ScripClipPower.docx

    Hello Jasper

    Attached is how I am using the TPS610985.

    The source of power is a 1.5V alkaline battery.

    That means my input voltage will vary between 0.9 and 1.6V. I also use a 1.8V supply for Mfg Test.

    A 3-input-NOR in discrete transistors controls the gate of of a P-channel MOSFET that starts the DC/DC converter.

    Power turn-on is initiated by either a user push-button, or application of the 1.5V power.

    The system processor then asserts the BOOT input and holds the power enable until it is ready to kill power.

    If a the ICE programmer is present, it will assert the PROG input and hold the power enabled until the programmer is disconnected.

    Once the DC/DC converter is active, its 3V output drives a N-channel source follower in parallel with the P-channel device.

    This is needed because low threshold P-channel MOSFETs have lousy On-Resistance.

    As long as any input to the 3-input NOR is true, the DC/DC converter is connected to the 1.5V supply.

    As soon as the P-channel path is disabled, the drive to the N-channel path is overridden, and the DC output is clamped by a 1K ohm load (speeds up the shutdown).

    If a 74AUP1G device existed for the 3-input NOR (74AUP1G27), I would use that, but have not found one.

    Assuming TI developed a version of the TPS610985 with a positive logic enable, then I could use a regular OR gate (74AUP1G332).

    Either way that would greatly reduce the glue that is currently employed.

    Cheers, Jack Gratteau

  • 0 in reply to Jack Gratteau25
    TI__Mastermind 46905 points

    Hi Jack,

    look like TPS610993 is Ok for this application if the WCSP package is acceptable.

    or maybe TPS61097A-33, which has very small shutdown current.

    let me if my understanding about the circuit is correct.

    1. S1 is off, Q4A off, Q2 is off, the TPS610985 is off.

    2. S1 is on, Q4A is on, Q2 is on, TPS610985 is on, then Q1 is on.

    3. the TPS610985 can be also turned on by BOOT and PROG to high logic.

    may i know the what is the voltage level of the BOOT and PROG? how to generate this signal if the battery is only 1.2V.

  • 0 in reply to Jasper Li
    TI__Mastermind 46905 points

    Hi Jack,

    one more question. what happen if the boost converter is always on? did you calculate the lifetime of the system?