Datasheet

5
LTC1474/LTC1475
FUNCTIONAL DIAGRA
UU
W
LTC1474: LBI
LTC1475: LBI/OFF
–
+
–
+
–
+
×
1µA
LBI/OFF
LBO
4.75µs
1-SHOT
1.23V
REFERENCE
GND
1474/75 FD
4
2
8
1.23V
1M
3M
(5V VERSION)
1.68M
(3.3V VERSION)
READY
STRETCH
V
CC
V
IN
V
IN
V
OUT
V
OUT
/V
FB
1×
C
ON
V
LB
ON
5Ω
SW
SENSE
R
SENSE
(OPTIONAL)
20×
100mV
WAKEUP
TRIGGER OUT
LTC1474: RUN
LTC1475: ON
1
5
6
7
+
+
×
CONNECTION NOT PRESENT IN LTC1474 SERIES
CONNECTION PRESENT IN LTC1474 SERIES ONLY
3
OUTPUT DIVIDER IS
IMPLEMENTED EXTERNALLY IN
ADJUSTABLE VERSIONS
PIN FUNCTIONS
UUU
V
OUT
/V
FB
(Pin 1): Feedback of Output Voltage. In the fixed
versions, an internal resistive divider divides the output
voltage down for comparison to the internal 1.23V refer-
ence. In the adjustable versions, this divider must be
implemented externally.
LBO (Pin 2): Open Drain Output of the Low Battery
Comparator. This pin will sink current when Pin 3 is below
1.23V.
LBI/OFF (Pin 3): Input to Low Battery Comparator. This
input is compared to the internal 1.23V reference. For the
LTC1475, a momentary ground on this pin puts regulator
in shutdown mode.
GND (Pin 4): Ground Pin.
SW (Pin 5): Drain of Internal PMOS Power Switch. Cath-
ode of Schottky diode must be closely connected to this
pin.
SENSE (Pin 6): Current Sense Input for Monitoring Switch
Current and Source of Internal PMOS Power Switch.
Maximum switch current is programmed with a resistor
between SENSE and V
IN
pins.
V
IN
(Pin 7): Main Supply Pin.
RUN/ON (Pin 8): On LTC1474, voltage level on this pin
controls shutdown/run mode (ground = shutdown, open/
high = run). On LTC1475, a momentary ground on this pin
puts regulator in run mode. A 100k series resistor must be
used between Pin 8 and the switch or control voltage.