LTC1149
LTC1149-3.3/LTC1149-5
High Efficiency Synchronous
Step-Down Switching Regulators
DESCRIPTIO
FEATURES
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Operation to 48V Input Voltage The LTC 1149 series is a family of synchronous step-
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Ultrahigh Efficiency: Up to 95% down switching regulator controllers featuring automatic
TM
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Current Mode Operation for Excellent Line and Burst Mode operation to maintain high efficiencies at
Load Transient Response low output currents. These devices drive external comple-
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High Efficiency Maintained over Wide Current Range mentary power MOSFETs at switching frequencies up
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Logic-Controlled Micropower Shutdown to 250kHz using a constant off-time current-mode archi-
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Short-Circuit Protection tecture.
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Very Low Dropout Operation: 100% Duty Cycle
Special onboard regulation and level-shift circuitry allow
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Synchronous FET Switching for High Efficiency
operation at input voltages from dropout to 48V (60V
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Adaptive Nonoverlap Gate Drives
absolute max). The constant off-time architecture main-
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Available in 16-Pin Narrow SO Package
tains constant ripple current in the inductor, easing the
design of wide input range converters. Current mode
APPLICATI S
operation provides excellent line and load transient
response. The operating current level is user-program-
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Notebook and Palmtop Computers
mable via an external current sense resistor.
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Portable Instruments
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Battery-Operated Digital Devices
The LTC1149 series incorporates automatic power saving
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Industrial Power Distribution
Burst Mode operation when load currents drop below the
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Avionics Systems
level required for continuous operation. Standby power is
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Telecom Power Supplies
reduced to only about 8mW at V = 12V. In shutdown,
IN
, LTC and LT are registered trademarks of Linear Technology Corporation.
both MOSFETs are turned off.
Burst Mode is a trademark of Linear Technology Corporation.
TYPICAL APPLICATI
V
IN
LTC1149-5 Efficiency
C
+
IN
1N4148
1N4148
100F
100
V
IN
FIGURE 1 CIRCUIT
100V
CAP
P-CHANNEL
PGATE V = 12V
IN
IRFR9024
0.068F
V 0.047F
CC
+
90
PDRIVE
D1
3.3F
V L*
CC R **
SENSE
1N5819
62H
0.05
V = 24V
V
OUT IN
LTC1149-5
5V/2A
80
+
SHDN1 SENSE
0V = NORMAL
1000pF
>2V = SHUTDOWN
SHDN2
SENSE
I
70
TH
+
N-CHANNEL
C
3300F OUT
C NGATE
T
IRFR024 220F
C
T
SGND P, RGNDS
1k
470pF
60
0.02 0.2 2
*COILTRONICS CTX62-2-MP
**KRL SL-1-C1-0R050J LOAD CURRENT (A)
1149 F01
1149 TA01
Figure 1. High Efficiency Step-Down Regulator
1
EFFICIENCY (%)
UO
UO
ULTC1149
LTC1149-3.3/LTC1149-5
ABSOLUTEXAI U RATI GS
PACKAGE/ORDER I FOR ATIO
Input Supply Voltage (Pin 2)...................... 15V to 60V
TOP VIEW
ORDER PART
V Output Current (Pin 3) .................................. 50mA
CC
1
16
CAP
NUMBER
PGATE
V Input Voltage (Pin 5)........................................ 16V
CC
2
15
SHDN2
V
IN
Continuous Output Current (Pins 4, 13) .............. 50mA
3
14
RGND
V
CC
LTC1149CN
Sense Voltages (Pins 8, 9)
4
13
NGATE
PDRIVE
LTC1149CN-3.3
V 12.7V .......................................... 13V to 0.3V
IN 5
12
PGND
V
CC
LTC1149CN-5
V < 12.7V............................. (V + 0.3V) to 0.3V
6
11
SGND
IN CC C
T
LTC1149CS
V /
FB
Shutdown Voltages (Pins 10, 15) ............................. 7V 7
10
I
TH
SHDN1*
LTC1149CS-3.3
+
8
9
SENSE
Operating Temperature Range .................... 0C to 70C SENSE
LTC1149CS-5
Extended Commercial
N PACKAGE
S PACKAGE
16-LEAD PDIP 16-LEAD PLASTIC SO
Temperature Range ............................... 40C to 85C
*FIXED OUTPUT VERSIONS
Junction Temperature (Note 1)............................ 125C
T = 125C, = 70C/ W (N)
JMAX JA
Storage Temperature Range ................ 65C to 150C T = 125C, = 110C/ W (S)
JMAX JA
Lead Temperature (Soldering, 10 sec)................. 300C
Consult factory for Industrial and Military grade parts.
ELECTRICAL CHARACTERISTICS T = 25C, V = 12V, V = 0V (Note 2), unless otherwise noted.
A IN 10
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V Feedback Voltage (LTC1149 Only) V = 9V l 1.21 1.25 1.29 V
10 IN
I Feedback Current (LTC1149 Only) l 0.2 1 A
10
V Regulated Output Voltage V = 9V
OUT IN
LTC1149-3.3 I = 700mA l 3.23 3.33 3.43 V
LOAD
LTC1149-5 I = 700mA l 4.9 5.05 5.2 V
LOAD
V Output Voltage Line Regulation V = 9V to 48V, I = 50mA 40 0 40 mV
OUT IN LOAD
Output Voltage Load Regulation
LTC1149-3.3 5mA < I < 2A l 40 65 mV
LOAD
LTC1149-5 5mA < I < 2A l 60 100 mV
LOAD
Burst Mode Output Ripple I = 0A 50 mV
LOAD P-P
I Input DC Supply Current (Note 3)
2
Normal Mode V = 12V 2.0 2.8 mA
IN
V = 48V 2.2 3.0 mA
IN
Burst Mode V = 12V 0.6 0.9 mA
IN
V = 48V 0.8 1.1 mA
IN
Shutdown V = 12V, V = 2V 135 170 A
IN 15
V = 48V, V = 2V 300 390 A
IN 15
V Internal Regulator Voltage V = 12V to 48V l 9.75 10.25 11 V
CC IN
(Sets MOSFET Gate Drive Levels) I = 20mA
3
V V V Dropout Voltage V = 5V, I = 10mA 200 250 mV
2 3 CC IN 3
V V P-Gate to Source Voltage (Off) V = 12V l 0.2 0 V
IN 1 IN
V = 48V l 0.2 0 V
IN
2
U WU U W W W