Datasheet

LTC1772B
5
1772bfa
PIN FUNCTIONS
FUNCTIONAL DIAGRAM
I
TH
/RUN (Pin 1): This pin performs two functions. It
serves as the error amplifi er compensation point as well
as the run control input. Nominal voltage range for this
pin is 0.85V to 1.9V. Forcing this pin below 0.35V causes
the device to be shut down. In shutdown all functions are
disabled and the PGATE pin is held high.
GND (Pin 2): Ground Pin.
V
FB
(Pin 3): Receives the feedback voltage from an external
resistive divider across the output.
SENSE
–
(Pin 4): The Negative Input to the Current Com-
parator.
V
IN
(Pin 5): Supply Pin. Must be closely decoupled to
GND Pin 2.
PGATE (Pin 6): Gate Drive for the External P-channel
MOSFET. This pin swings from 0V to V
IN
.
SWITCHING
LOGIC AND
BLANKING
CIRCUIT
–
+
–
+
0.5μA
0.3V
OVP
SHORT-CIRCUIT
DETECT
SHDN
1.2V
UV
1772FD
V
REF
+
60mV
V
REF
0.8V
V
IN
RS1
VOLTAGE
REFERENCE
SLOPE
COMP
ICMP
R
S
Q
FREQ
FOLDBACK
OSC
SENSE
–
V
IN
5
2
4
–
+
4
EAMP
V
FB
–
+
3
PGATE
V
IN
6
I
TH
/RUN
V
IN
0.35V
V
REF
0.8V
1
–
+
SHDN
CMP
GND
–
+
UNDERVOLTAGE
LOCKOUT
15mV