LTC3872-1_15 Datasheet, PDF (6/20 Pages) Linear Technology – No RSENSE Current Mode Boost DC/DC Controller

LTC3872-1
Pin Functions (TS8/DD8)
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.
Functional Diagram
V_IN
GND
SW
UNDERVOLTAGE ^UV
LOCKOUT
VOLTAGE
REFERENCE
1.2V
SLOPE
COMPENSATION
SHUTDOWN
COMPARATOR
0.7µA
RUN/SS
SHDN
INTERNAL
SOFT-START
RAMP
+
I_TH
BUFFER
–
–+
CURRENT
COMPARATOR
I_LIM
IPRG
RS ^{R S}
LATCH _Q
550kHz
OSCILLATOR
CURRENT LIMIT
CLAMP
ERROR
AMPLIFIER
SWITCHING
LOGIC CIRCUIT
V_IN
NGATE
V_FB
1.2V
I_TH
38721 FD
38721f
6
For more information www.linear.com/LTC3872-1