Post Go back to editing

LT8607 behavior during reversed input

I have a system where the output of my regulator may be held high when the system input voltage is absent - basically, exactly the situation mentioned in the LT8607 datasheet (page 15).  While I understand that this may cause the LT8607 to draw its quiescent current from the output (and this is OK for my system), my concern is whether this situation can cause the regulator to actually begin switching.  The scenario would be when an external voltage is applied that is higher than the target voltage (5V), causing more than 5V to be present on VIN.  I have run into this situation with another regulator, it would begin switching the low-side switch, essentially turning the regulator into a backwards boost converter, generating a very high voltage (>60!) on VIN.  I want to be sure that the LT8607 won't do this.

  •  If EN/UV pin is low, or Vout is higher than regulated point, LT8607 won't switch.

    LT8607 has burst mode and pulse skipping mode. Neither one will cause boosted Vin problem.

  • Thanks for this.  I finally got around to purchasing the LT8607 eval board and testing this condition (power applied to the output when no input voltage is present).  While I do NOT see any boosted VIN, I DO see some switching activity when the externally applied output voltage is between about 3V - 5V.  This is actually very similar to the regulator I am hoping to replace, although that other device boosts VIN, while the LT8607 does not, at least not by any significant amount.

    But still - could you help me understand why the LT8607 is switching at all in this case, and to give me some confidence that this will not lead to a boosted VIN in some other situation?  Perhaps an explanation of why the LT8607 switches with the externally applied voltage, and why this is not leading to a boosted VIN.