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LM43600 The relation of Vin-min-st and Vin

masahiko shimizu
Guru 11235 points
Other Parts Discussed in Thread: LM43600

Hi,

My customer is using LM43600.
He has a question about the relation of Vin-min-st and Vin.

Vin-min-st value is showed as max 3.8V in datasheet.
But this device can operate from Vin=3.5V (min).

Could you let me know the relation of Vin-min-st and Vin, please?
-> If customer uses internal LDO as Figure 45 in datasheet, does you recommend that Vin is over 3.8V for LDO good operation?
and If customer uses external bias as Figure 44, does you recommend that Vin is over 3.8V until that Vout is over 3.3V(It shows no problem that Vin is 3.5V after that Vout is over 3.3V)?

Best regards,
Shimizu

  • 0
    TI__Genius 16025 points
    Masahiko-san,

    The startup VIN is 3.8V and the running minimum VIN is 3.5V. There is the possibility of part to part variation, hence some parts can push these limits higher or lower.

    In your application, If the customer uses internal LDO (BIAS tied to GND), VIN has to be at 3.8V during startup and 3.5V during running.
    If the customer uses BIAS tied to Vout, the same rule applies, VIN only has to be at 3.8V during startup and 3.5V during running.

    This is to ensure clean operation. However the part c

    The internal LDO will switch between external supply (if connected) or internal depending on which is the more reliable source.

    Thanks,
    Anston
  • 0 in reply to Anston Lobo
    Guru 11235 points
    Hi Anston,

    Thank you for your support.
    I add a question.

    Is there the rule of time period from startup 3.8V to 3.5V?
    -> This is a question about time to have to maintain 3.8V at start up.

    Best regards,
    Shimizu
  • 0 in reply to masahiko shimizu
    TI__Genius 16025 points
    Shimizu,

    As soon as the part has soft start has ended or as soon as Vout is regulating, it is then capable of handling 3.5V on Vin.

    Thanks,
    Anston