The internal LDO has a lower EN threshold than the
output of the regulator. The internal LDO regulates the VCC voltage
at 3.3V, typically when:
- The EN
pin voltage is above 1.1V (maximum).
- The EN
pin voltage is below the precision enable threshold
for the output voltage.
The precision enable circuitry is ON after VCC is above the
UVLO. The internal power MOSFETs of the SW node remain off unless
the voltage on the EN terminal goes above the precision enable
threshold. The
LM614xxT-Q1 also employs
UVLO protection. If the VCC voltage is below the UVLO level, the
output of the regulator is turned off.