Datasheet LTC3801, LTC3801B (Analog Devices) - 4

LTC3801/LTC3801B
U U U PI FU CTIO S ITH/RUN (Pin 1):
This pin performs two functions. It
SENSE– (Pin 4):
Current Sense Pin. An external sense serves as the error amplifier compensation point as well as resistor is connected between this pin and VIN (Pin 5). the run control input. Nominal voltage range for this pin is
V
0.7V to 1.9V. Forcing this pin below 0.6V causes the
IN (Pin 5):
Supply Pin. This pin must be closely de- coupled to GND (Pin 2). device to be shut down. In shutdown, all functions are disabled and the PGATE pin is held high.
PGATE (Pin 6):
Gate Drive for the External P-Channel MOSFET. This pin swings from 0V to V
GND (Pin 2):
Ground Pin. IN.
VFB (Pin 3):
Receives the feedback voltage from an exter- nal resistor divider across the output.
U U W FU CTIO AL DIAGRA
4 SENSE– 15mV (LTC3801B) VIN 5 BURST UNDERVOLTAGE UV SLOPE VOLTAGE DEFEAT BURST 0.8V COMPENSATION LOCKOUT REFERENCE (LTC3801B) CLAMP + – 1µA (LTC3801) CURRENT SHUTDOWN 2µA (LTC3801B) COMPARATOR ITH/RUN – COMPARATOR 0.3V 1 + ILIM ITH + SHDN BUFFER – R S 550kHz RS OSCILLATOR LATCH Q VIN FREQUENCY SLEEP SWITCHING FOLDBACK – COMPARATOR LOGIC AND PGATE 6 SLEEP BLANKING BURST CIRCUIT DEFEAT + (LTC3801B) 0V SOFT-START CLAMP OVERVOLTAGE SHORT-CIRCUIT 0.15V COMPARATOR DETECT ERROR – + + – AMPLIFIER 0.225V – 0.88V 0.3V VFB 3 + 1.2V 0.8V GND 2 3801 FD sn3801 3801fs 4