ADP1612ARMZ-R7 datasheet(12/28 Pages) AD

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ADP1612/ADP1613

Rev. A | 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

VIN and VOUT. 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.

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