LTC1771_15 Datasheet, PDF (5/16 Pages) Linear Technology – 10A Quiescent Current High Efficiency Step-Down DC/DC Controller

LTC1771
PI FU CTIO S
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.
W
FUNCTIONAL BLOCK DIAGRA
V_IN
1µA
C_{SS RUN/SS}
1
MODE
(BURST ENABLE)
8
READY
1.23V
V_OUT
+ ^ON
SOFT-START
EA
–
10% CURRENT
*
I_TH
2
R_C
C_{C GND}
4
2V
1V
–
B
1V ⁺
SLEEP
READY
*OPTIONAL FOR FOLDBACK
CURRENT LIMITING
MODE
ON TRIGGER
1-SHOT
STRETCH
3.5µs
1.23V
REFERENCE
10% CURRENT
C
ON
V_IN
6
22k
V_IN
+
C_IN
R_SENSE
SENSE
7
250k
BLANKING
V_IN
PGATE
5
D1
L
R2
V_FB
3
R1
V_OUT
+
C_OUT
1771 BD
5