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PDF LT1372CS8 Data sheet ( Hoja de datos )
| Número de pieza | LT1372CS8 | |
| Descripción | 500kHz and 1MHz High Efficiency 1.5A Switching Regulators | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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LT1372/LT1377
500kHz and 1MHz
High Efficiency
1.5A Switching Regulators
FEATURES
s Faster Switching with Increased Efficiency
s Uses Small Inductors: 4.7µH
s All Surface Mount Components
s Only 0.5 Square Inch of Board Space
s Low Minimum Supply Voltage: 2.7V
s Quiescent Current: 4mA Typ
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
APPLICATIONS
s Boost Regulators
s CCFL Backlight Driver
s Laptop Computer Supplies
s Multiple Output Flyback Supplies
s Inverting Supplies
DESCRIPTION
The LT®1372/LT1377 are monolithic high frequency
switching regulators. They can be operated in all standard
switching configurations including boost, buck, flyback,
forward, inverting and “Cuk.” A 1.5A high efficiency switch
is included on the die, along with all oscillator, control and
protection circuitry. All functions of the LT1372/LT1377
are integrated into 8-pin SO/PDIP packages.
The LT1372/LT1377 typically consumes only 4mA quies-
cent current and has higher efficiency than previous parts.
High frequency switching allows for very small inductors
to be used. All surface mount components consume less
than 0.5 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 APPLICATION
5V-to-12V Boost Converter
5V L1*
4.7µH
D1
MBRS120T3
OFF ON 4 S/S
5
VIN VSW 8
+ C1**
22µF
LT1372/LT1377
2
FB
GND
6, 7
VC
1
C2
0.047µF
R3
2k
R1
53.6k
1%
+
R2
6.19k
1%
C3
0.0047µF
VOUT†
12V
C4**
22µF
*COILCRAFT DO1608-472 (4.7µH) OR
COILCRAFT DT3316-103 (10µH) OR
SUMIDA CD43-4R7 (4.7µH) OR
SUMIDA CD73-100KC (10µH) OR
**AVX TPSD226M025R0200
†MAX IOUT
L1 IOUT
4.7µH 0.25A
10µH 0.35A
LT1372 • TA01
12V Output Efficiency
100
VIN = 5V
90
80
70
60
50
0.01
0.1
OUTPUT CURRENT (A)
1
LT1372 • TA02
1
1 page  
LT1372/LT1377
PIN FUNCTIONS
VC (Pin 1): The Compensation 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 per-
formed 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 250µA
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 100k 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 600kHz and 800kHz (LT1372) or 1.2MHz to 1.6MHz
(LT1377).
VIN (Pin 5): Bypass input supply pin 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 DIAGRAM
S/S
SHUTDOWN
DELAY AND RESET
VIN
LOW DROPOUT
2.3V REG
ANTI-SAT
SW
SYNC
OSC
LOGIC
DRIVER
SWITCH
100k
NFB
50k
+
NFBA
–
5:1 FREQUENCY
SHIFT
COMP
FB
1.245V
REF
GND SENSE
–
EA
+
+
IA
–
VC AV ≈ 6
0.08Ω
GND LT1372 • BD
5
5 Page 
LT1372/LT1377
TYPICAL APPLICATIONS N
Positive-to-Negative Converter with Direct Feedback
Dual Output Flyback Converter with Overvoltage Protection
+
ON
OFF
C3
0.0047µF
VIN
2.7V TO 16V
C1
22µF
4
S/S
5
VIN VSW 8
LT1372/LT1377
3
NFB
VC GND
1 6, 7
T1*
D2 2
P6KE-15A
4
•
D3
1N4148
•
1
3
D1
MBRS130LT3
+ C4
47µF
R2
2.49k
1%
R3
2.49k
1%
–VOUT†
–5V
C2
0.047µF
R1
2k
*COILTRONICS CTX10-2 (407) 241-7876
†MAX IOUT
IOUT VIN
0.3A 3V
0.5A 5V
0.75A 9V
LT1372 • TA03
R2
1.21k
1%
R1
13k
1%
+ C1
22µF
2
OFF
ON
4
FB
S/S
VIN
2.7V TO 13V
5
VIN
VSW
8
MBRS140T3
T1*
2, 3
P6KE-20A •
5
+
1N4148
6, 7
•4
8
+
LT1372/LT1377
3
NFB
•
1
VC GND
1 6, 7
MBRS140T3
C3
0.0047µF
C2
0.047µF
R3
2k
*DALE LPE-4841-100MB (605) 665-9301
VOUT
15V
C4
47µF
C5
47µF
–VOUT
R4 –15V
12.1k
1%
R5
2.49k
1%
LT1372 • TA04
90% Efficient CCFL Supply
Low Ripple 5V to – 3V “Cuk”† Converter
VIN L1*
5V 2 3
C1
22µF
10V
+
1• •4
5
VIN
VSW
4
S/S
7 LT1372/LT1377
GND NFB
6
GND S
VC
8
3
1
C2
47µF
16V
+
D1**
C5
0.0047µF
*SUMIDA CLS62-100L
**MOTOROLA MBR0520LT3
†PATENTS MAY APPLY
R4
2k
C4
0.047µF
VOUT
–3V
250mA
R1
1k
1%
C6
0.1µF
+
R2
4.99k
1%
C3
47µF
16V
LT1372 • TA05
VIN
4.5V
TO 30V +
10µF
C2
27pF
54
5mA MAX
LAMP
10
32
T1
1
C1
0.1µF
D1
1N4148
330Ω
Q1
Q2
2.7V TO
5.5V +
2.2µF
1N5818
5
L1
33µH
D2
1N4148
OFF
ON
4
S/S
VIN 8
VSW
LT1372/LT1377
GND
6, 7
2
VFB
VC
+1
2µF
562Ω*
10k
20k
DIMMING
22k
1N4148
0.1µF
OPTIONAL REMOTE
DIMMING
LT1372 • TA06
C1 = WIMA MKP-20
CCFL BACKLIGHT APPLICATION CIRCUITS
L1 = COILCRAFT DT3316-333
CONTAINED IN THIS DATA SHEET ARE
Q1, Q2 = ZETEX ZTX849 OR ROHM 2SC5001 COVERED BY U.S. PATENT NUMBER 5408162
T1 = COILTRONICS CTX 110609
AND OTHER PATENTS PENDING
* = 1% FILM RESISTOR
DO NOT SUBSTITUTE COMPONENTS
COILTRONICS (407) 241-7876
COILCRAFT (708) 639-6400
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 LT1372CS8.PDF ] | |
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