Datasheet

ADP1612/ADP1613 Data Sheet
Rev. D | Page 12 of 28
THERMAL SHUTDOWN (TSD)
The ADP1612/ADP1613 include TSD protection. If the die
temperature exceeds 150°C (typical), TSD turns off the NMOS
power device, significantly reducing power dissipation in the
device and preventing output voltage regulation. The NMOS
power device remains off until the die temperature reduces to
130°C (typical). The soft start capacitor is discharged during
TSD to ensure low output voltage overshoot and inrush
currents when regulation resumes.
UNDERVOLTAGE LOCKOUT (UVLO)
If the input voltage is below the UVLO threshold, the ADP1612/
ADP1613 automatically turn off the power switch and place
the part into a low power consumption mode. This prevents
potentially erratic operation at low input voltages and prevents
the power device from turning on when the control circuitry
cannot operate it. The UVLO levels have ~100 mV of hysteresis
to ensure glitch free startup.
ENABLE/SHUTDOWN CONTROL
The EN input turns the ADP1612/ADP1613 regulator on or
off. Drive EN low to turn off the regulator and reduce the
input current to 0.01 µA, typical. Drive EN high to turn on
the regulator.
When the step-up dc-to-dc switching converter is in shutdown
mode (EN ≤ 0.3 V), there is a dc path from the input to the output
through the inductor and output rectifier. This causes the output
voltage to remain slightly below the input voltage by the forward
voltage of the rectifier, preventing the output voltage from dropping
to ground when the regulator is shutdown. Figure 37 provides a
circuit modification to disconnect the output voltage from the
input voltage at shutdown.
Regardless of the state of the EN pin, when a voltage is applied to
VIN of the ADP1612/ADP1613, a large current spike occurs due
to the nonisolated path through the inductor and diode between
V
IN
and V
OUT
. The high current is a result of the output capacitor
charging. The peak value is dependent on the inductor, output
capacitor, and any load active on the output of the regulator.