ADP1864

Rev. 0 | Page 9 of 16

SHORT-CIRCUIT PROTECTION

If there is a short across the output load, the voltage at the

feedback pin (FB) drops rapidly. When the FB voltage drops

below 0.35 V, the ADP1864 reduces the oscillator frequency

to 190 kHz. The increase in the oscillator period allows the

inductor additional time to discharge, preventing the output

current from running away. Once the output short is removed

and the feedback voltage increases above the 0.35 V threshold,

the oscillator frequency returns to 580 kHz.

UNDERVOLTAGE LOCKOUT (UVLO)

To prevent erratic operation when the input voltage drops

below the minimum acceptable voltage, the ADP1864 has an

undervoltage lockout (UVLO) feature. If the input voltage drops

below 2.90 V, PGATE is pulled high. The ADP1864 will

continue to draw its typical quiescent current. Current

consumption continues to drop toward the shutdown current as

input voltage is reduced. The ADP1864 is re-enabled and begins

switching once the IN voltage is increased above the UVLO

rising threshold (3.0 V).

OVERVOLTAGE LOCKOUT PROTECTION (OVP)

The ADP1864 provides an overvoltage protection feature to

protect the system against output short circuits to a higher

voltage supply. If the feedback voltage increases to 0.885 V,

PGATE is held high, turning the external FET off. The FET

continues to be held high until the voltage at FB decreases to

0.84 V, at which time the ADP1864 resumes normal operation.

SOFT START

The ADP1864 includes a soft start feature that limits the rate of

increase in inductor current once the part is enabled. Soft start

is activated when the input voltage is increased above the

UVLO threshold or COMP is released from GND. Soft start

limits the inrush current at the input and also limits the output

voltage overshoot. The soft start control slope is set internally.