LT1308A/LT1308B
PIN FUNCTIONS
V
C
(Pin 1/Pin 1):
Compensation Pin for Error Amplifier.
Connect a series RC from this pin to ground. Typical
values are 47kΩ and 100pF. Minimize trace area at V
C
.
FB (Pin 2/Pin 2):
Feedback Pin. Reference voltage is
1.22V. Connect resistive divider tap here. Minimize trace
area at FB. Set V
OUT
according to:
V
OUT
= 1.22V(1 + R1/R2).
SHDN (Pin 3/Pin 3):
Shutdown. Ground this pin to turn
off switcher. To enable, tie to 1V or more. SHDN does not
need to be at V
IN
to enable the device.
GND (Pin 4/Pins 4, 5, 6, 7):
Ground. Connect directly to
local ground plane. Ground plane should enclose all
components associated with the LT1308. PCB copper
connected to these pins also functions as a heat sink. For
the TSSOP package, connect all pins to ground copper to
get the best heat transfer. This keeps chip heating to a
minimum.
6
U
U
U
(SO/TSSOP)
SW (Pin 5/Pins 8, 9, 10):
Switch Pins. Connect inductor/
diode here. Minimize trace area at these pins to keep EMI
down. For the TSSOP package, connect all SW pins
together at the package.
V
IN
(Pin 6/Pins 11, 12):
Supply Pins. Must have local
bypass capacitor right at the pins, connected directly to
ground. For the TSSOP package, connect both V
IN
pins
together at the package.
LBI (Pin 7/Pin 13):
Low-Battery Detector Input. 200mV
reference. Voltage on LBI must stay between –100mV
and 1V. Low-battery detector does not function with
SHDN pin grounded. Float LBI pin if not used.
LBO (Pin 8/Pin 14):
Low-Battery Detector Output. Open
collector, can sink 50μA. A 220kΩ pull-up is recom-
mended. LBO is high impedance when SHDN is grounded.
1308abfa
LINER [ LINEAR TECHNOLOGY ]
