Datasheet

5
LTC1771
–
+
EA
–
+
C
ON
ON
+
C
SS
RUN/SS
V
IN
V
OUT
V
IN
1
MODE
MODE
READY
SLEEP
READY
250k
22k R
SENSE
1.23V
1V
1V
2V
1µA
(BURST ENABLE)
10% CURRENT
10% CURRENT
SOFT-START
8
V
IN
V
IN
V
OUT
L
C
IN
+
C
OUT
R2
D1
R1
6
SENSE
7
PGATE
3.5µs
1771 BD
5
V
FB
3
I
TH
R
C
C
C
*
* OPTIONAL FOR FOLDBACK
CURRENT LIMITING
2
GND
4
+
–
B
ON TRIGGER
1.23V
REFERENCE
BLANKING
1-SHOT
STRETCH
FUNCTIONAL BLOCK DIAGRA
UU
W
RUN/SS (Pin 1): The voltage level on this pin controls
shutdown/run mode (ground = shutdown, open/high =
run). Connecting an external capacitor to this pin provides
soft-start.
I
TH
(Pin 2): Error Amplifier Compensation Point. The
current comparator threshold increases with this control
voltage. Nominal voltage range for this pin is 0V to 3V.
V
FB
(Pin 3): Feedback of Output Voltage for Comparison
to Internal 1.23V Reference. An external resistive divider
across the output is returned to this pin.
GND (Pin 4): Ground Pin.
PGATE (Pin 5): High Current Gate Driver for External
P-Channel MOSFET Switch. Voltage swing is from ground
to V
IN
.
V
IN
(Pin 6): Main Input Voltage Supply Pin.
SENSE (Pin 7): Current Sense Input for Monitoring Switch
Current. Maximum switch current and Burst Mode
threshold is programmed with an external resistor be-
tween SENSE and V
IN
.
MODE (Pin 8): Burst Mode Enable/Disable Pin. Connect-
ing this pin to V
IN
(or above 2V) enables Burst Mode
operation, while connecting this pin to ground disables
Burst Mode operation. Do not leave floating.
UU
U
PI FU CTIO S