lt1373hv Linear Technology Corporation, lt1373hv Datasheet - Page 5

• Manufacturer Part Number: lt1373hv
• Description: 250khz Low Supply Current High Efficiency 1.5a Switching Regulator
• Manufacturer: Linear Technology Corporation

BLOCK DIAGRA
PI FU CTIO S
V
frequency compensation, current limiting and soft start. It
is the output of the error amplifier and the input of the
current comparator. Loop frequency compensation can be
performed with an RC network connected from the V
to ground.
FB (Pin 2): The feedback pin is used for positive output
voltage sensing and oscillator frequency shifting. It is the
inverting input to the error amplifier. The noninverting
input of this amplifier is internally tied to a 1.245V
reference. Load on the FB pin should not exceed 100 A
when the NFB pin is used. See Applications Information.
NFB (Pin 3): The negative feedback pin is used for negative
output voltage sensing. It is connected to the inverting
input of the negative feedback amplifier through a 400k
source resistor.
S/S (Pin 4): Shutdown and Synchronization Pin. The S/S
pin is logic level compatible. Shutdown is active low and
the shutdown threshold is typically 1.3V. For normal
operation, pull the S/S pin high, tie it to V
C
U
(Pin 1): Compensation Pin. The V
U
NFB
FB
GND SENSE
1.245V
400k
REF
U
200k
S/S
W
FEEDBACK
NEGATIVE
–
–
+
+
ERROR
DELAY AND RESET
SYNC
AMP
AMP
SHUTDOWN
250kHz
OSC
C
pin is used for
5:1 FREQUENCY
IN
SHIFT
or leave it
C
LOW DROPOUT
pin
V
2.3V REG
C
COMP
LOGIC
V
IN
floating. To synchronize switching, drive the S/S pin be-
tween 300kHz and 340kHz.
V
more. The part goes into undervoltage lockout when V
drops below 2.5V. Undervoltage lockout stops switching
and pulls the V
GND S (Pin 6): The ground sense pin is a “clean” ground.
The internal reference, error amplifier and negative feed-
back amplifier are referred to the ground sense pin. Con-
nect it to ground. Keep the ground path connection to the
output resistor divider and the V
free of large ground currents.
GND (Pin 7): The ground pin is the emitter connection of
the power switch and has large currents flowing through it.
It should be connected directly to a good quality ground
plane.
V
switch and has large currents flowing through it. Keep the
traces to the switching components as short as possible to
minimize radiation and voltage spikes.
IN
SW
(Pin 5): Input Supply Pin. Bypass V
(Pin 8): The switch pin is the collector of the power
A
V
CURRENT
6
AMP
+
–
C
pin low.
DRIVER
ANTI-SAT
C
compensation network
GND
SW
SWITCH
0.08
LT1373 • BD
IN
with 10 F or
LT1373
5
IN