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TPS723-Q1: TPS72301 FB pin

York Lee
Prodigy 10 points
Part Number: TPS723-Q1
Other Parts Discussed in Thread: TPS723, PMP30473

Hello, 

We are planning to -5V output voltage in our product. There are few questions about TPS723 series. 

  1. Since TPS723 typical output is -2.5V, in order to generate -5V, it is necessary to use TPS72301 only, but TPS72325. Is it correct?
  2. According to the datasheet, Pin4 is NR. But TPS72301 is not NR, it is FB pin for the resistor devider. Is it still recommand that connect the bypass capacitor on FB pin for noise reduction?

    Best Regards, 

    York
  • +1
    TI__Genius 14320 points

    Hi York,

    TPS72325-Q1 has a fixed -2.5V output. For that device, pin 4 is the NR pin and should be connected to a capacitor to reduce output noise.

    To generate -5V, you will need to use the TPS72301-Q1 with an external resistor divider connected from OUT to pin 4 (FB) to set the output voltage. Instructions on calculating the divider values can be found in section 7.3.7 of the datasheet. Do not place a capacitor from pin 4 of the adjustable TPS72301-Q1 to GND - doing so will cause the LDO to become unstable. 

    Best Regards,

    Alex Davis

  • 0 in reply to Alex Davis
    Prodigy 10 points

    Hi Alex, 

    Thanks for the reply. 1 question i forgot to ask. 

    In the reference design PMP30473, there is a 1000pF capacitor on pin4 FB and pin5 OUT. What is the purpose to put this capacitor here?

  • 0 in reply to York Lee
    TI__Genius 14320 points

    Hi York,

    Adding a feedforward capacitor between Vout and Vfb can help improve noise and transient performance of the LDO. This Application Note describes the pros and cons of a feedforward capacitor in more detail. 

    Best Regards,

    Alex Davis