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TPS54525 5Vin and Vreg5 Behaviour

Mike Ulrich
Expert 3110 points
Other Parts Discussed in Thread: TPS54525

Hi,

What happens to VREG5 when the input is only 5V?

The datasheet sates VREG5 must be above the UVLO threshold for the device to function, and in order to get VREG5 to output a voltage the input must be greater than 5.6V. This confuses me since this device can handle an input voltage down to 4.5V. Please help clarify.

Thank You,

Mike Ulrich

  • 0
    TI__Guru**** 191445 points
    VREG5 is derived from VIN with an internal LDO. When VIN is lower that the nominal LDO output voltage, VREG5 will decrease to VIN minus the drop out voltage (not specified but probably around 200 mV) The TPS54525 will operate with VREG 5 much lower than 5 V. Look in the EC table page 4, in the UVLO section. UVLO is derived from VREG5 not VIN. TPS54525 becomes active when VREG5 is above 3.91 V max and turns off again when VREG5 falls below 3.42 V max.