Datasheet

4
LTC1772
1772fb
FUNCTIONAL DIAGRA
UU
W
SWITCHING
LOGIC AND
BLANKING
CIRCUIT
–
+
–
+
0.5µA
0.3V
0.3V
OVP
SHORT-CIRCUIT
DETECT
SHDN
1.2V
UV
1772 FD
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
V
IN
0.15V
–
+
BURST
CMP
SLEEP
PIN FUNCTIONS
UUU
I
TH
/RUN (Pin 1): This pin performs two functions. It
serves as the error amplifier compensation point as well as
the run control input. The current comparator threshold
increases with this control voltage. Nominal voltage range
for this pin is 0.7V 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 exter-
nal 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
.