• State Resolved
  • Locked Locked
  • Replies 2 replies
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 203 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TPS7A91: Eliminate dropout by bridging IN/OUT: allowed?

GGA
Genius 3985 points
Part Number: TPS7A91
Other Parts Discussed in Thread: TPS7A52

Hi,

we need to vary PA output of a certain FEM.
This chip is currently (its a given design, in production) sourced by 3.3V - which is neccessary for max PA output. To achieve lower output I need to reduce VCC_TX, e.g. in 4 steps between 1.5 - 3.3 V. My plan is to to vary R2 between certain values, using e.g. solder bridged parallel resistors:

But: VIN is 3.3V and VOUT needs to be 3.3V in case of max PA. Am I allowed to bridge VIN with VOUT in that case without damaging something?

Same question on

thx

GGA

  • 0
    TI__Mastermind 43720 points

    Hi CGA,

    While it is OK to dynamically adjust VOUT as proposed. Bridging VIN to VOUT, bypasses the LDO altogether so it would not be able to regulate or limit the current. 

    Another Option might be to use the TPS7A52. This has a maximum VDO of 65mV at 2A so if you set VOUT to 3.3V, and VIN is 3.3V, at 1A VOUT would only be 32.5mV below VIN. So in effect, this would behave like a well-regulated switch. 

    Let me know what you think.

  • 0 in reply to JCHK
    Genius 3985 points

    JCK,

    thanks for suggestion.

    TPS7A52 looks nice but exceeds the budget by far.

    So I guess that bridging would do the job, it's done once when customers deploy that module into their product and it's not needed to change during product lifetime.