LTC3872-1
6
38721f
For more information www.linear.com/LTC3872-1
IPRG (Pin 1/Pin 4): Current Sense Limit Select Pin.
I
TH
(Pin 2/Pin 3): Error Amplifier Compensation Point.
Nominal voltage range for this pin is 0.7V to 1.9V.
V
FB
(Pin 3/Pin 2): Receives the feedback voltage from an
external resistor divider across the output.
GND (Pin 4/Pin 1, Exposed Pad Pin 9): Ground. The ex
-
posed pad must be soldered to PCB ground for electrical
contact and rated thermal performance.
NGATE (Pin 5/Pin 8): Gate Drive for the External N-Channel
MOSFET. This pin swings from 0V to V
IN
.
V
IN
(Pin 6/Pin 7): Supply Pin. This pin must be closely
decoupled to GND.
RUN/SS (Pin 7/Pin 6): Shutdown and external soft-start
pin. In shutdown, all functions are disabled and the NGATE
pin is held low.
SW (Pin 8/Pin 5): Switch node connection to inductor and
current sense input pin through external slope compensa
-
tion resistor. Normally, the external N-channel MOSFET’s
drain is connected to this pin.
RUN/SS
V
IN
SWGND
I
TH
V
FB
NGATE
IPRG
SLOPE
COMPENSATION
550kHz
OSCILLATOR
CURRENT
COMPARATOR
SR
Q
V
IN
VOLTAGE
REFERENCE
UNDERVOLTAGE
LOCKOUT
–
+
I
TH
BUFFER
SWITCHING
LOGIC CIRCUIT
CURRENT LIMIT
CLAMP
INTERNAL
SOFT-START
RAMP
– +
I
LIM
RS
LATCH
1.2V
1.2V
UV
SHUTDOWN
COMPARATOR
SHDN
ERROR
AMPLIFIER
0.7µA
–
+
pin FuncTions
(TS8/DD8)
FuncTional DiagraM