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TPS63021: Vout setting and range

Part Number: TPS63021
Other Parts Discussed in Thread: TPS63020

Dear Sirs,

We want to use TPS63021 chip in our design. As I understand from datasheet TPS63021 contains internal divider on FB pin. The electrical characteristics show that TPS63021_FB input impedance (apparently, sum internals R1 + R2) is equal 1MOhm. 

I have some questions about TPS63021:

  1. Can I add an additional resistor Rext between FB and Vout pins to change the output voltage level (Vout)?
  2. What is the range of Vout can I set with the help Rext between FB and Vout pins?
  3. Can I set Vout = 3V3? What is Rext value I should set between FB and Vout pins for Vout = 3V3?
  4. What are the values ​​of the Rup and Rdown resistors at the FB input (pin) inside TPS63021 chip (figure 4. Functional Block Diagram (TPS63021) of datasheet)?
  5. Can I set Vout voltage with the help  Vout = Vref * (1+ (Rext + Rpu) / Rdown)) equation? Where Vref = 0.5V, Rext - resistor between FB and Vout, Rup and Rdown resistors at FB input inside TPS63021 chip. Is it correctly?
  • Hi Slava,

    I don't suggest to do that as the integrated resistor has large variation over process and temperature. the VOUT would has large variation if you uses external resistor to change the VOUT. Why not use TPS63020

  • Hi Jusper,

    thanks for your reply.

    Customer has some problems with posting messages on this forum, so I provide the reply from him just AS IS below.

    Dear Mr. Jasper Li,

     Thank you very much for your answer! This question was for our company. But unfortunately, I have not received complete answers to our questions.

     Our design contains TPS63020 chip. We have a problem with its buy and delivery of TPS63020 chip. TPS63020 and TPS63021 is pin-to-pin chips. I want set TPS63021 instead TPS63020 to our boards temporarily.

     TPS63020 have Vin=2V2-5V2 / Vout = 3V3 / Iout max = 1A in our design.

     Can I have answers on my last post questions for a complete understanding of the operation of TPS63021 chip?

    1. Can I use TPS63021 instead TPS63020 in our design temporarily?
    2. What is Rext value I should set between FB and Vout pins for Vout = 3V3?

     Best regards,


    Developer engineer, Fort-Telecom, Perm, Russia.

  • Slava,

    the TPS63021 is a fixed 3.3V device of the TPS63020. it can be used instead of TPS63020. FB pin should be connected to VOUT for fixed version device, so the Rext is zero. refer to the PIN function description in page 4.