Datasheet ADP1864 (Analog Devices) - 9

Data Sheet ADP1864 SHORT-CIRCUIT PROTECTION OVERVOLTAGE LOCKOUT PROTECTION (OVP)
If there is a short across the output load, the voltage at the The ADP1864 provides an overvoltage protection feature to feedback pin (FB) drops rapidly. When the FB voltage drops protect the system against output short circuits to a higher below 0.35 V, the ADP1864 reduces the oscil ator frequency voltage supply. If the feedback voltage increases to 0.885 V, to 190 kHz. The increase in the oscil ator period al ows the PGATE is held high, turning the external FET off. The FET inductor additional time to discharge, preventing the output continues to be held high until the voltage at FB decreases to current from running away. Once the output short is removed 0.84 V, at which time the ADP1864 resumes normal operation. and the feedback voltage increases above the 0.35 V threshold,
SOFT START
the oscil ator frequency returns to 580 kHz. The ADP1864 includes a soft start feature that limits the rate of
UNDERVOLTAGE LOCKOUT (UVLO)
increase in the inductor current once the part is enabled. Soft To prevent erratic operation when the input voltage drops start is activated when the input voltage is increased above the below the minimum acceptable voltage, the ADP1864 has an UVLO threshold or COMP is released from GND. Soft start undervoltage lockout (UVLO) feature. If the input voltage limits the inrush current at the input and limits the output drops below 2.90 V, PGATE is pul ed high and the ADP1864 voltage overshoot. The soft start control slope is set internally. continues to draw its typical quiescent current. Current consump- tion 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). Rev. C | Page 9 of 16 Document Outline Features Applications General Description Typical Applications Diagram Revision History Specifications Absolute Maximum Ratings ESD Caution Pin Configuration and Function Descriptions Typical Performance Characteristics Theory of Operation Loop Startup Short-Circuit Protection Undervoltage Lockout (UVLO) Overvoltage Lockout Protection (OVP) Soft Start Applications Information ADIsimPower Design Tool Duty Cycle Ripple Current Sense Resistor Inductor Value MOSFET Diode Input Capacitor Output Capacitor Feedback Resistors Layout Considerations Example Applications Circuits Outline Dimensions Ordering Guide