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TPS7A33: Maximum capacitance at TPS7A3301RGWR output

Amit Gade
Prodigy 80 points
Part Number: TPS7A33


Tool/software:

Hi

We are planning to use TPS7A4701RGWR and TPS7A3301RGWR to generate +2.5 and -2.5V on our board from 5V and -5V supply's.

In our daughter cards we have capacitance of around 700uF(100uF on each card X 7 boards) on same common voltage rails (+2.5 and -2.5V) and our load current requirement is around 250mA

can you please confirm above mentioned regulators can be use with higher capacitance (700uf) values?

 

  • 0
    TI__Genius 15470 points

    Hi Amit,

    Neither TPS7A4701 nor TPS7A3301 lists a maximum output capacitance requirement for stability. Inrush current during startup is a concern with so much output capacitance. This can be mitigated by using larger NR/SS capacitors for a slower startup ramp rate. 

    Best Regards,

    Alex Davis

  • 0 in reply to Alex Davis
    Prodigy 80 points

    Hi Alex,

    Thanks for the quick response, can you please let me know what is the maximum NR/SS capacitance value we can use with TPS7A4701 and TPS7A3301

  • 0 in reply to Amit Gade
    TI__Genius 15470 points

    Hi Amit,

    There's not really an upper limit to the NR/SS capacitance that can be used for either device. Larger NR/SS values will cause slower and slower startup times. A longer soft-start could possibly experience power dissipation issues if downstream loads pull significant amounts of current while the LDO is still starting up, as the voltage drop across the LDO will be larger during startup than in steady-state operation. 

    Best Regards,

    Alex Davis

  • 0 in reply to Alex Davis
    Prodigy 80 points

    Hi Alex,

    Thanks for the information.

    Also we want to review the full power supply schematic from TI which consist of TPS7A4701RGWR (Vout +2.5V), TPS7A3301RGWR (Vout -2.5V), TPSM63602RDHR (Vout -5V) and LMQ61460AFSQRJRRQ1 (Vout +5V). Can you please share the respective email contact details to review this schematic?

  • 0 in reply to Amit Gade
    TI__Genius 15470 points

    Hi Amit,

    You can contact me at a-davis6@ti.com. 

    Best Regards, 

    Alex Davis