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PDF LT3668 Data sheet ( Hoja de datos )
| Número de pieza | LT3668 | |
| Descripción | 40V 400mA Step-Down Switching Regulator | |
| Fabricantes | Linear Technology Corporation | |
| Logotipo |  |
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LT3668
Features
40V 400mA Step-Down
Switching Regulator with Dual
Fault Protected Tracking LDOs
Description
n Dual Low Dropout Linear Tracking Regulators
200mA Outputs with Programmable Current Limits
1.6V to 45V Input Range
Fault Protected to ±45V
n Triple Output Supply from a Single Input Requires
Only One Inductor
n IQ = 50μA at 12VIN to 6V and 5V with No Load
n Buck Regulator:
Low Ripple (<15mVP-P) Burst Mode Operation®
400mA Output with Internal Power Switch
4.3V to 40V Input Operation Range (60V Max)
n Adjustable 250kHz to 2.2MHz Switching Frequency
n Power Good Indicator
n Available in a Thermally-Enhanced 16-Lead MSOP
Package
Applications
n Fault-Protected Sensor Supply
n Automotive and Industrial Supplies
n Power for Portable Instrumentation
L, LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks
of Linear Technology Corporation. All other trademarks are the property of their respective
owners.
The LT®3668 is a monolithic triple power supply composed
of a 400mA buck switching regulator and two 200mA low
dropout linear tracking regulators (LDOs).This provides a
complete and robust power solution for applications that
require the power supply of a sensor to tightly track the
power supply of a measurement ASIC.
Each tracking LDO supplies 200mA of output current with
a typical dropout voltage of 340mV, and each LDO has an
accurate resistor programmable current limit.
Internal protection circuitry includes reverse-battery
protection, current limiting, thermal limiting and reverse
current protection.
The buck regulator includes a high efficiency switch, a
boost diode, and the necessary oscillator, control and
logic circuitry. Current mode topology is used for fast
transient response and good loop stability. Low ripple
Burst Mode operation maintains high efficiency at low
output currents while keeping output ripple below 15mV
in a typical application.
The LT3668 is available in a thermally-enhanced 16-lead
MSOP package with exposed pad for low thermal resis-
tance.
Typical Application
VIN
7V TO 40V
TRANSIENT
TO 60V
4.7µF IN1
BOOST
SW
ON OFF
f = 600kHz 174k
EN
PG
RT
LT3668
DA
IN3/BD
IN2
FB1
5V
150mA
(FOLLOWS
OUT3)
10µF
ADJ2
OUT2
ADJ3
OUT3
EN2/ILIM2 GND EN3/ILIM3
0.22µF 27µH
22pF
232k
931k
294k
10µF
5V
150mA
6V
100mA
22µF
3668 TA01a
For more information www.linear.com/LT3668
100
90
80
70
60
50
40
30
20
10
0
5
No-Load Supply Current
10 15 20 25 30
INPUT VOLTAGE (V)
35
3668 TA01b
3668f
1
1 page  
LT3668
Typical Performance Characteristics TA = 25°C, unless otherwise noted.
Efficiency, VOUT1 = 3.3V
90
80
70 VIN1 = 24V
60
50
VIN1 = 12V
VIN1 = 36V
40
30
20
10
0
0.01
FRONT PAGE APPLICATION
BUCK REGULATOR ONLY
VOUT1 = 3.3V
L: MSS7341-223MLB
0.1 1
10
LOAD CURRENT (mA)
100
3668 G01
No-Load Supply Current
100
FRONT PAGE APPLICATION
90
80
70
60
50
40
30
20
10
0
5 10 15 20 25 30
INPUT VOLTAGE (V)
35 40
3668 G04
Maximum Load Current
700
FRONT PAGE APPLICATION
650
600
TYPICAL
550
500
450 MINIMUM
400
5 10 15 20 25 30 35 40
INPUT VOLTAGE (V)
3668 G07
Efficiency, VOUT1 = 6V
100
90
80
VIN1 = 24V
VIN1 = 12V
70
60 VIN1 = 36V
50
40
30
20
10
0
0.01
FRONT PAGE APPLICATION
BUCK REGULATOR ONLY
VOUT1 = 6V
L: MSS7341-273MLB
0.1 1 10
LOAD CURRENT (mA)
100
3668 G02
No-Load Supply Current
FRONT PAGE APPLICATION
CATCH DIODE: CMMSH1-60
1m
INCREASED SUPPLY CURRENT
DUE TO CATCH DIODE LEAKAGE
AT HIGH TEMPERATURE
100µ
10µ
–50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
3668 G05
Switching Regulator
Load Regulation
0.10
0.08
FRONT PAGE APPLICATION
REFERENCED FROM VOUT1 AT 200mA LOAD
0.06
0.04
0.02
0
–0.02
–0.04
–0.06
–0.08
–0.10
0
50 100 150 200 250 300 350 400
LOAD CURRENT (mA)
3668 G08
VFB1 vs Temperature
1.30
1.25
1.20
1.15
1.10
–50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
3668 G03
Maximum Load Current
700
FRONT PAGE APPLICATION
650 VOUT1 = 3.3V
600 TYPICAL
550
500 MINIMUM
450
400
5 10 15 20 25 30 35 40
INPUT VOLTAGE (V)
3668 G06
Switch Current Limit
800
SWITCH PEAK
CURRENT LIMIT
700
600
CATCH DIODE VALLEY CURRENT LIMIT
500
400
0
20 40 60 80 100
DUTY CYCLE (%)
3668 G09
For more information www.linear.com/LT3668
3668f
5
5 Page 
Block Diagram
LT3668
VOUT2
C4
11
IN2
9
ADJ2
10 OUT2
LDO
DRIVER
ERROR
AMPLIFIER
EN2/
12 ILIM2
14 PG
80Ω +
0.4V – CURRENT LIMIT
AMPLIFIER
+ LDO
1V –
DISABLE
7
ADJ3
ERROR
A+MPLIFIER
–
LDO
DRIVER
CURRENT LIMIT
AMPLIFIER
LDO
DISABLE
+
–
5
IN3/
BD
80Ω
0.4V
+
– 1V
OUT3 6
EN3/
ILIM3
13
VOUT3
C5
VIN1 15 IN1
C1
3 EN
INTERNAL REF
1.2V
ERROR
AMPLIFIER
+–
1.08V
1.32V
+
–
VC
–
+
SLOPE COMP
OSCILLATOR
250kHz TO 2.2MHz
Burst Mode
DETECT
GND FB1
17 8
R2 R1
RT
4
RT
BOOST
DIODE
R
Q
S
–
+
CATCH DIODE
CURRENT LIMIT
B00ST 2
SW 1
DA 16
C2
L1
D1 C3
VOUT1
3668 BD
For more information www.linear.com/LT3668
3668f
11
11 Page | ||
| Páginas | Total 28 Páginas | |
| PDF Descargar | [ Datasheet LT3668.PDF ] | |
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