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TPS62172: Grounding the PG pin and some design issues

Will
Prodigy 250 points
Part Number: TPS62172

Dear TI experts,

I want to use TPS62172 to convert 3.7V of lipo battery to 3.3V output.

Can I ask 4 design related questions?

1. Can the 100kΩ pull-up resistor in the picture above be removed if I don't use the PG pin and connect it to ground?
2. The current of my system is about 20mA. Do I need to add extra resistance on the basis of the above picture?
3. Regarding the 2.2uH inductor, can VLS252012ET-2R2M be used in addition to the recommended model on page 14 of the datasheet? Does current matter?

4. If it's always on, can I just short the Vin and EN pins in the layout?

Best regards,

Will

  • +1
    TI__Expert 7860 points

    Hi Will,

    Answers to questions below.

    1. Can the 100kΩ pull-up resistor in the picture above be removed if I don't use the PG pin and connect it to ground?

    Yes, this pull-up resistor may be removed, PG pin can be tied to ground or may be left floating.
    2. The current of my system is about 20mA. Do I need to add extra resistance on the basis of the above picture?

    No extra resistance is required, the current rating is typically given as a maximum current spec.
    3. Regarding the 2.2uH inductor, can VLS252012ET-2R2M be used in addition to the recommended model on page 14 of the datasheet? Does current matter?

    This inductor is acceptable, however I did notice that the DCR (dc resistance) of this inductor is quite large compared to newer components. Since you will be operating close to 100% duty cycle you may want to pick an inductor with a lower DCR to ensure plenty of margin incase your battery voltage drops. For your 20mA application, saturation current won't be a big issue since the current rating is around 1.5A. 

    4. If it's always on, can I just short the Vin and EN pins in the layout?

    Yes, you can tie Vin and EN pins together.

    Hope this helps.

    Thanks,

    Joseph