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PDF LT1572CS Data sheet ( Hoja de datos )
| Número de pieza | LT1572CS | |
| Descripción | 100kHz/ 1.25A Switching Regulator with Catch Diode | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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FEATURES
s Catch Diode Included in Package
s Wide Input Voltage Range: 3V to 30V
s Low Quiescent Current: 6mA
s Internal 1.25A Switch
s Very Few External Parts Required
s Self-Protected Against Overloads
s Operates in Nearly All Switching Topologies
s Shutdown Mode Draws Only 50µA Typical Current
s Can Be Externally Synchronized
APPLICATI S
s 3.3V-to-5V and 5V-to-12V Boost Converters
s Negative-to-Positive Converter
s SEPIC Converter (Input Can Be Greater or
Less Than Output)
s Battery Charger
LT1572
100kHz, 1.25A Switching
Regulator with Catch Diode
DESCRIPTIO
The LT®1572 is a 1.25A 100kHz monolithic switching
regulator with on-board switch and catch diode included
in one package. It combines an LT1172 with a 1A Schottky
catch diode. The LT1572 can be operated in all standard
switching configurations, including boost, buck, SEPIC,
flyback, forward, inverting and “Cuk”. All necessary con-
trol, oscillator and protection circuitry is included on the
die with the high efficiency switch. This makes the part
extremely easy to use and provides “bustproof” operation
similar to that obtained with 3-pin linear regulators.
The LT1572 operates with supply voltages from 3V to 30V
and draws only 6mA quiescent current. It can deliver load
power up to 15W with no external power devices. By
utilizing a current mode switching technique, the LT1572
achieves excellent response to load and line transients.
The LT1572 has many unique features not found on the
more difficult to use control chips presently available. It
uses adaptive anti-sat switch drive to allow very wide
ranging load currents with no loss in efficiency. An exter-
nally activated shutdown mode reduces total supply cur-
rent to 50µA typical for standby operation. External syn-
chronizing of switching frequency is possible, with a range
of 120kHz to 160kHz.
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATI
VIN
4.5V
TO 10V
5V-to-12V Boost Converter
+ C3
100µF
10V
L1*
50µH
*COILTRONICS CTX50-2
**AVX TPS OR SPRAGUE 593D
9
11 2 15
†ALWAYS CONNECT BOTH ANODE (2, 15)
VIN VSW ANODE† 3 AND CATHODE (3, 14) PINS
CATHODE† 14
LT1572
FB
E1 E2 GND VC
10 12 4, 13 5
R3
1k
C1
1µF
R1
10.7k
1%
R2
1.24k
1%
12V
0.25A
+ C2**
100µF
16V
LT1572 • TA01
Boost Converter Efficiency
100
BOOST CONVERTER
VIN = 5V
90 VOUT = 12V
80
70
60
50
0
50 100 150 200
L0AD CURRENT (mA)
250
LT1572 • TA01
1
1 page  
TYPICAL PERFOR A CE CHARACTERISTICS
LT1572
Supply Current vs Supply Voltage
(Shutdown Mode)
160
TJ = 25°C
140
120
100
80 VC = 50mV
60
40
20
0
0
VC = 0V
10 20 30
SUPPLY VOLTAGE (V)
40
1572 G07
Driver Current* vs Switch Current
40
35
30
25
TJ = – 55°C
20
15
TJ = ≥ 25°C
10
5
0
0 0.25 0.50 0.75 1.00 1.25
SWITCH CURRENT (A)
1572 G08
* AVERAGE POWER SUPPLY CURRENT IS
FOUND BY MULTIPLYING DRIVER CURRENT BY
DUTY CYCLE, THEN ADDING QUIESCENT CURRENT.
Supply Current vs Input Voltage*
15
14 TJ = 25°C
13 NOTE THAT THIS CURRENT DOES NOT
INCLUDE DRIVER CURRENT, WHICH IS
12 A FUNCTION OF LOAD CURRENT AND
DUTY CYCLE.
11
10 90% DUTY CYCLE
9 50% DUTY CYCLE
8
7 10% DUTY CYCLE
6 0% DUTY CYCLE
5
0 10 20 30 40 50 60
INPUT VOLTAGE (V)
1572 G09
* UNDER VERY LOW OUTPUT CURRENT CONDITIONS,
DUTY CYCLE FOR MOST CIRCUITS WILL APPROACH
10% OR LESS.
Shutdown Mode Supply Current
200
180
160
140
120 TJ = 150°C
100
80
60
–55°C ≤ TJ ≤ 125°C
40
20
0
0 10 20 30 40 50 60 70 80 90 100
VC PIN VOLTAGE (mV)
1572 G10
Idle Supply Current
vs Temperature
11
10 VC = 0.6V
9
8
7 VSUPPLY = 60V
6 VSUPPLY = 3V
5
4
3
2
1
–75 –50 –25 0 25 50 75 100 125 150
TEMPERATURE (°C)
1572 G13
Error Amplifier Transconductance
5000
4500
4000
gm
=
∆I
∆V
(VC
(FB
PIN)
PIN)
3500
3000
2500
2000
1500
1000
500
0
–75 –50 –25 0 25 50 75 100 125 150
TEMPERATURE (°C)
1572 G11
Feedback Pin Clamp Voltage
500
450
400
350 –55°C
300 25°C
250
150°C
200
150
100
50
0
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
FEEDBACK CURRENT (mA)
1572 G14
VC Pin Characteristics
300
200 VFB = 1.5V (CURRENT INTO VC PIN)
100
0
–100
TJ = 25°C
–200
–300
VFB = 0.8V (CURRENT OUT OF VC PIN)
–400
0
0.5 1.0 1.5 2.0 2.5
VC PIN VOLTAGE (V)
1572 G12
Switch “Off” Characteristics
1000
900
800
700
600
500 VSUPPLY
= 3V
400
300 VSUPPLY VSUPPLY
= 15V = 40V
200
100
0
0 10 20 30 40 50 60 70 80 90 100
SWITCH VOLTAGE (V)
1572 G15
5
5 Page 
TYPICAL APPLICATI S
Negative Buck Converter
LT1572
* REQUIRED IF INPUT LEADS ≥ 2"
** PULSE ENGINEERING 92114
COILTRONICS 50-2-52
+
C3*
100µF
VIN
–7V TO –20V
CATHODE
VIN
VSW
E1 LT1572 ANODE
E2
GND
FB
VC
C1
R3
L1**
50µH
R2
1.24k
C2
200µF
R1
4.64k
Q1
2N3906
R4
12k
LOAD
–5.2V
0.75A
1572 TA03
INPUT VOLTAGE†
4.5V TO 20V
10µF +
TANT
Backlight CCFL Supply (see AN55 for details)
1k
CATHODE
E2
VIN
VSW
LT1572 ANODE
E1
GND
FB
VC
+
2µF
L2***
L1**
300µH
A
Q1*
33pF
3kV LAMP
0.02µF
Q2*
B
D1
1N914
R3
10k
D2
1N914
R1
560Ω
50k
INTENSITY
ADJUST
C6 * Q1,Q2 = BCP56 OR MPS650/561
1µF ** COILTRONICS CTX300-4
*** SUMIDA 6345-020 OR COILTRONICS 110092-1
† A MODIFICATION WILL ALLOW OPERATION DOWN TO 4.5V. CONSULT FACTORY.
1572 TA04
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 its circuits as described herein will not infringe on existing patent rights.
11
11 Page | ||
| Páginas | Total 12 Páginas | |
| PDF Descargar | [ Datasheet LT1572CS.PDF ] | |
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