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PDF LT1373CS8 Data sheet ( Hoja de datos )
| Número de pieza | LT1373CS8 | |
| Descripción | 250kHz Low Supply Current High Efficiency 1.5A Switching Regulator | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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FEATURES
s 1mA IQ at 250kHz
s Uses Small Inductors: 15µH
s All Surface Mount Components
s Only 0.6 Square Inch of Board Space
s Low Minimum Supply Voltage: 2.7V
s Constant Frequency Current Mode
s Current Limited Power Switch: 1.5A
s Regulates Positive or Negative Outputs
s Shutdown Supply Current: 12µA Typ
s Easy External Synchronization
s 8-Pin SO or PDIP Packages
U
APPLICATIO S
s Boost Regulators
s CCFL Backlight Driver
s Laptop Computer Supplies
s Multiple Output Flyback Supplies
s Inverting Supplies
LT1373
250kHz Low Supply Current
High Efficiency
1.5A Switching Regulator
DESCRIPTIO
The LT®1373 is a low supply current high frequency
current mode switching regulator. It can be operated in all
standard switching configurations including boost, buck,
flyback, forward, inverting and “Cuk.” A 1.5A high effi-
ciency switch is included on the die, along with all oscilla-
tor, control and protection circuitry. All functions of the
LT1373 are integrated into 8-pin SO/PDIP packages.
Compared to the 500kHz LT1372, which draws 4mA of
quiescent current, the LT1373 switches at 250kHz, typi-
cally consumes only 1mA and has higher efficiency. High
frequency switching allows for small inductors to be used.
All surface mount components consume less than 0.6
square inch of board space.
New design techniques increase flexibility and maintain
ease of use. Switching is easily synchronized to an exter-
nal logic level source. A logic low on the shutdown pin
reduces supply current to 12µA. Unique error amplifier
circuitry can regulate positive or negative output voltage
while maintaining simple frequency compensation tech-
niques. Nonlinear error amplifier transconductance re-
duces output overshoot on start-up or overload recovery.
Oscillator frequency shifting protects external compo-
nents during overload conditions.
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO
5V-to-12V Boost Converter
5V L1*
22µH
D1
MBRS120T3
OFF ON 4 S/S
5
VIN VSW 8
+ C1**
22µF
LT1373
2
FB
GND
6, 7
VC
1
C2
0.01µF
R3
5k
R1
215k
1%
+
R2
24.9k
1%
VOUT†
12V
C4**
22µF
†MAX IOUT
L1 IOUT
15µH 0.3A
22µH 0.35A
*SUMIDA CD75-220KC (22µH) OR
COILCRAFT D03316-153 (15µH)
**AVX TPSD226M025R0200
LT1373 • TA01
12V Output Efficiency
100
VIN = 5V
f = 250kHz
90
80
70
60
50
1
10 100 1000
OUTPUT CURRENT (mA)
LT1373 • TA02
1
1 page  
LT1373
PI FU CTIO S
VC (Pin 1): Compensation Pin. The VC pin is used for
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 VC pin
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 100µA
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 VIN or leave it
floating. To synchronize switching, drive the S/S pin be-
tween 300kHz and 340kHz.
VIN (Pin 5): Input Supply Pin. Bypass VIN with 10µF or
more. The part goes into undervoltage lockout when VIN
drops below 2.5V. Undervoltage lockout stops switching
and pulls the VC pin low.
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 VC compensation network
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.
VSW (Pin 8): The switch pin is the collector of the power
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.
BLOCK DIAGRA
S/S
400k
NFB
200k
SHUTDOWN
DELAY AND RESET
VIN
LOW DROPOUT
2.3V REG
SYNC
250kHz
OSC
LOGIC
+
NEGATIVE
FEEDBACK
– AMP
5:1 FREQUENCY
SHIFT
COMP
ANTI-SAT
SW
DRIVER
SWITCH
FB
1.245V
REF
GND SENSE
–
ERROR
+ AMP
+
CURRENT
AMP
–
VC AV ≈ 6
0.08Ω
GND LT1373 • BD
5
5 Page 
TYPICAL APPLICATIO S
Low Ripple 5V to – 3V “Cuk”† Converter
VIN L1*
5V 2 3
VOUT
–3V
250mA
C1 +
22µF
10V
1• •4
5
VIN
VSW
4
S/S
7 LT1373
GND NFB
6
GND S
VC
8
3
1
C2
47µF
16V
+
D1**
*SUMIDA CLS62-100L
**MOTOROLA MBR0520LT3
†PATENTS MAY APPLY
R4
5k
C4
0.01µF
R1
1k
1%
C6
0.1µF
+
R2
5.49k
1%
C3
47µF
16V
LT1373 • TA05
LT1373
PACKAGE DESCRIPTION Dimensions in inches (millimeters) unless otherwise noted.
0.300 – 0.325
(7.620 – 8.255)
N8 Package
8-Lead PDIP (Narrow 0.300)
(LTC DWG # 05-08-1510)
0.045 – 0.065
(1.143 – 1.651)
0.130 ± 0.005
(3.302 ± 0.127)
0.400*
(10.160)
MAX
87 65
0.009 – 0.015
(0.229 – 0.381)
0.065
(1.651)
TYP
+0.035
0.325 –0.015
( )8.255
+0.889
–0.381
0.100
(2.54)
BSC
*THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.
MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.010 INCH (0.254mm)
0.125
(3.175)
MIN
0.018 ± 0.003
(0.457 ± 0.076)
0.020
(0.508)
MIN
0.255 ± 0.015*
(6.477 ± 0.381)
12
34
N8 1098
S8 Package
8-Lead Plastic Small Outline (Narrow 0.150)
(LTC DWG # 05-08-1610)
0.010
(0.254
–
–
0.020
0.508)
×
45°
0.008 – 0.010
(0.203 – 0.254)
0.053 – 0.069
(1.346 – 1.752)
0°– 8° TYP
0.016 – 0.050
(0.406 – 1.270)
0.014 – 0.019
(0.355 – 0.483)
TYP
*DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
**DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD
FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
0.004 – 0.010
(0.101 – 0.254)
0.050
(1.270)
BSC
0.228 – 0.244
(5.791 – 6.197)
0.189 – 0.197*
(4.801 – 5.004)
8 765
1 2 34
0.150 – 0.157**
(3.810 – 3.988)
SO8 1298
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tation that the interconnection of circuits as described herein will not infringe on existing patent rights.
11
11 Page | ||
| Páginas | Total 12 Páginas | |
| PDF Descargar | [ Datasheet LT1373CS8.PDF ] | |
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