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TPS65320D-Q1: Max Vin for LDO when buck is disabled

Lenio Cacula
Genius 16700 points
Part Number: TPS65320D-Q1

With regards to the following information from the datasheet:

With the buck disabled or the buck output voltage out of regulation (VFB1 less than 91% of Vref),
the buck regulator switches the LDO input automatically to the input voltage.

For this customer application, the battery can potentially reach 30V, which is well within the range of the buck, but it is above the 20V max for the LDO. Is that a problem? Can you explain exactly what the parameter VIN-VIN_LDO means in the absolute maximum ratings table of the datasheet? (section 6.1)

Thank you!

  • 0
    TI__Mastermind 20590 points
    Hi Lenio,

    Today is a public holiday in the US. This thread has been assigned and will be addressed next week after the holiday.
  • 0
    TI__Genius 9380 points

    Lenio,
    The normal operations for this part is designed so that when the vehicle is starting or running that the buck is turned on. In this case the LDO never sees the high voltages.
    example: When the vehicle is turned off the controller goes to sleep or enters low power mode, then the buck turns off and the LDO is supplied from the input (Battery) and the LDO continues to supply the controller at a lower current. The moment the key is turned, the buck is turned on changing the LDO input to the buck output. Then the load transient pulses or load dump is seen by the buck and not the LDO.
    _
    Yes, if the LDO were to see 30V, that would be a problem. The LDO has a max input of 20V.
    The idea behind the VIN-VIN_LDO statement is that this is the maximum input voltage as long as the LDO is not powered by the input.
    VIN max 40V
    LDO max 20V
    (VIN-VIN_LDO)VIN if the LDO is powered off of the buck max 40V

    Let me know if you have anymore questions.