LTC3801B_15 Datasheet, PDF (4/12 Pages) Linear Technology – Micropower Constant Frequency Step-Down DC/DC Controllers in ThinSOT

LTC3801/LTC3801B
PI FU CTIO S
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. Nominal voltage range for this pin is
0.7V to 1.9V. Forcing this pin below 0.6V 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 resistor divider across the output.
SENSE^– (Pin 4): Current Sense Pin. An external sense
resistor is connected between this pin and V_IN (Pin 5).
V_IN (Pin 5): Supply Pin. This pin must be closely de-
coupled to GND (Pin 2).
PGATE (Pin 6): Gate Drive for the External P-Channel
MOSFET. This pin swings from 0V to V_IN.
W
FU CTIO AL DIAGRA
5 ^VIN
UNDERVOLTAGE ^UV
LOCKOUT
VOLTAGE
REFERENCE
BURST
0.8V
DEFEAT BURST
(LTC3801B) CLAMP
4
SENSE^–
15mV (LTC3801B)
+–
SLOPE
COMPENSATION
1 ^ITH/RUN
1µA (LTC3801)
2µA (LTC3801B)
–
SHUTDOWN
COMPARATOR
+
SHDN
+
I_TH
BUFFER
–
BURST
DEFEAT
(LTC3801B)
SLEEP
– ^COMPARATOR
SLEEP
+
0.15V
0.225V
SOFT-START
CLAMP
ERROR
AMPLIFIER
CURRENT
COMPARATOR
0.3V
I_LIM
RS ^{R S}
LATCH Q
SWITCHING
LOGIC AND
BLANKING
CIRCUIT
0V
OVERVOLTAGE
COMPARATOR
0.88V
550kHz
OSCILLATOR
V_IN
FREQUENCY
FOLDBACK
PGATE
6
SHORT-CIRCUIT
DETECT
+–
0.3V
V_FB
3
1.2V
0.8V
GND
2
3801 FD
4
sn3801 3801fs