LTC3801 LINER [Linear Technology], LTC3801 Datasheet - Page 4

• Manufacturer Part Number: LTC3801
• Description: Micropower Constant Frequency Step-Down DC/DC Controllers in ThinSOT
• Manufacturer: LINER [Linear Technology]

PI FU CTIO S
LTC3801/LTC3801B
I
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
nal resistor divider across the output.
FU CTIO AL DIAGRA
4
TH
5
1
FB
(LTC3801B)
U
/RUN (Pin 1): This pin performs two functions. It
V
I
DEFEAT
TH
BURST
U
IN
(Pin 3): Receives the feedback voltage from an exter-
/RUN
U
1 A (LTC3801)
2 A (LTC3801B)
U
UNDERVOLTAGE
LOCKOUT
0.15V
U
–
+
–
+
COMPARATOR
COMPARATOR
SHUTDOWN
UV
SLEEP
SLEEP
SHDN
0.225V
W
REFERENCE
VOLTAGE
1.2V
SOFT-START
CLAMP
AMPLIFIER
ERROR
0.8V
(LTC3801B)
DEFEAT
–
+
BURST
SENSE
resistor is connected between this pin and V
V
coupled to GND (Pin 2).
PGATE (Pin 6): Gate Drive for the External P-Channel
MOSFET. This pin swings from 0V to V
+
–
IN
BUFFER
I
0.8V
TH
(Pin 5): Supply Pin. This pin must be closely de-
CLAMP
BURST
–
(Pin 4): Current Sense Pin. An external sense
0.3V
OVERVOLTAGE
COMPARATOR
LATCH
+
RS
0.88V
SWITCHING
–
LOGIC AND
BLANKING
CIRCUIT
R
I
Q
LIM
S
4
–
0V
GND
SENSE
COMPARATOR
+
2
15mV (LTC3801B)
CURRENT
–
V
COMPENSATION
IN
0.3V
OSCILLATOR
+
IN
550kHz
SLOPE
.
FREQUENCY
FOLDBACK
–
IN
SHORT-CIRCUIT
(Pin 5).
DETECT
PGATE
V
FB
3801 FD
3801f
6
3