Datasheet

5
LT1303/LT1303-5
PIN FUNCTIONS
UUU
GND (Pin 1): Signal Ground. Tie to PGND under the
package.
LBO (Pin 2): Open-Collector Output of Low-Battery Com-
parator. Can sink 100µA. Disabled when device is in
shutdown.
SHDN (Pin 3): Shutdown. Pull high to shut down the
device. Ground for normal operation.
FB/Sense (Pin 4): On 1303 (adjustable) this pin connects
to the main comparator C1 input. On LT1303-5 this pin
connects to the resistor string that sets output voltage
at 5V.
LBI (Pin 5): Low-Battery Comparator Input. When voltage
on this pin below 1.24V, LBO is low.
V
IN
(Pin 6): Supply Pin. Must be bypassed with a large
value electrolytic to ground. Keep bypass within 0.2" of the
device.
SW (Pin 7): Switch Pin. Connect inductor and diode here.
Keep layout short and direct to minimize radio frequency
interference.
PGND (Pin 8): Power ground. Tie to signal ground (pin1)
under the package. Bypass capacitor from V
IN
should be
tied directly to PGND within 0.2" of the device.
W
IDAGRA
B
L
O
C
K
S
Figure 2. LT1303 Block Digram
–
+
–
+
–
+
6 7
8
3
25
1
4
++
C1 C2
L1
D1
V
IN
V
IN
R1
3Ω
Q2
1×
Q1
160×
SHUTDOWN
LBOLBIGND
PGND
SW
R1
R2
C3
C2
C1
FB
OFF
OSCILLATOR
A3
DRIVER
CURRENT 
COMPARATOR
HYSTERETIC
COMPARATOR
REFERENCE
1.24V
18mV
LT1303 BD01