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TPS74701 Enable sequence

Other Parts Discussed in Thread: TPS74701

Using the TPS74701 LDO with a the Enable controlled by a seprate signal (not Vin or Vbias). Ven = 1.8V, Vin = 1.3V, Vbias = 3.3V. Is there a concern if Ven is applied before Vin or Vbias? 

I see in the data sheet sequencing section 8.1.4 that VIn, Vbias and VEN can be sequenced in any order, but the last sentence in that paragraph indicates that VEN can be controlled by a seperate signal if it is applied after Vin and Vbias.This implies a sequencing requirement.  I assume there could be a current leakage problem if the Enable is applied before a power supply because of ESD diodes. Can a series resistor (10k?) be used to limit this current? Or are there other concerns?

  • Hi Mark,

    Vin, Vbias, and Ven can be sequenced in any order without damaging the LDO.  The remainder of the section explains that for the soft-start function to operate as designed, sequencing does matter.  Furthermore, if Vbias and Ven are present without Vin, the device will output 50uA of current.  

    Essentially, the sequencing of the rails does impact how the device startsup; however, it will not damage the device.

    Very Respectfully,