Datasheet LTC3700 (Analog Devices) - 6

LTC3700
U U U PIN FUNCTIONS VIN2 (Pin 1):
LDO Input Supply Pin. Must be closely
VIN (Pin 7):
Buck Input Supply Pin. Must be closely decoupled to GND (Pin 5). decoupled to GND (Pin 5).
LDO (Pin 2):
LDO Output Pin. Must be closely decoupled
SENSE– (Pin 8):
The Negative Input to the Current Com- to GND (Pin 5) with a low ESR ceramic capacitor ≥ 2.2µF. parator of the Buck. Monitors switch current of external P-Channel MOSFET.
VFB2 (Pin 3):
LDO Feedback Voltage. Receives the feed- back voltage from an external resistor divider between
VFB (Pin 9):
Buck Feedback Voltage. Receives the feed- LDO (Pin 2) and GND (Pin 5). back voltage from an external resistor divider between buck output and GND (Pin 5).
PGOOD (Pin 4):
Open-Drain Power Good Output. This pin will pull to ground if either voltage output of the buck or the
ITH/RUN (Pin 10):
This pin performs two functions. It LDO [sensed at VFB (Pin 9) and VFB2 (Pin 3), respectively] serves as the error amplifier compensation point for the is out of range. When both voltage outputs are valid, this buck, as well as a common run control input for both the pin will go to a high impedance state. buck and the LDO. The current comparator threshold of the buck increases with this voltage. Nominal voltage
GND (Pin 5):
Common Ground Pin for Both Buck and LDO. range for this pin is 0.7V to 1.9V. Forcing this pin below
PGATE (Pin 6):
Gate Drive for Buck’s External P-Channel 0.3V causes both the buck and the LDO to be shut down. MOSFET. This pin swings from 0V to VIN. In shutdown all functions are disabled, the PGATE pin is held high and the LDO output will go to a high impedance state. 3700f 6