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LTC1142/LTC1142L/LTC1142HV
Dual High Efficiency
Synchronous Step-Down
Switching Regulators
, LTC and LT are registered trademarks of Linear Technology Corporation.
The LTC
®
1142/LTC1142L/LTC1142HV are dual synchro-
nous step-down switching regulator controllers featuring
automatic Burst Mode
TM
operation to maintain high efficien-
cies at low output currents. The devices are composed of two
separate regulator blocks, each driving a pair of external
complementary power MOSFETs, at switching frequencies
up to 250kHz, using a constant off-time current mode archi-
tecture providing constant ripple current in the inductor.
The operating current level for both regulators is user pro-
grammable via an external current sense resistor. Wide input
supply range allows operation from 3.5V* to 18V (20V
maximum). Constant off-time architecture provides low drop-
out regulation limited only by the R
DS(ON)
of the external
MOSFET and resistance of the inductor and current sense
resistor.
The LTC1142 series is ideal for applications requiring dual
output voltages with high conversion efficiencies over a wide
load current range in a small amount of board space.
■
Dual Outputs: 3.3V and 5V or User Programmable
■
Ultrahigh Efficiency: Over 95% Possible
■
Current Mode Operation for Excellent Line and Load
Transient Response
■
High Efficiency Maintained over 3 Decades of
Output Current
■
Low Standby Current at Light Loads: 160µA/Output
■
Independent Micropower Shutdown: I
Q
< 40µA
■
Wide V
IN
Range: 3.5V to 20V
■
Very Low Dropout Operation: 100% Duty Cycle
■
Synchronous FET Switching for High Efficiency
■
Available in Standard 28-Pin SSOP
■
Notebook and Palmtop Computers
■
Battery-Operated Digital Devices
■
Portable Instruments
■
DC Power Distribution Systems
Figure 1. High Efficiency Dual 3.3V, 5V Supply
1000pF
+
+
+
1000pF
PDRIVE 3
SENSE
+
3
SENSE
–
3
NDRIVE 3
PGND3 SGND3 C
T3
I
TH3
I
TH5
C
T5
SGND5
PGND5
NDRIVE 5
SENSE
–
5
SENSE
+
5
PDRIVE 5
V
IN3
SHDN3
SHDN5
V
IN5
LTC1142HV
C
T5
390pF
4 3 25 27 13 11 17 18
R
C5
1k
C
C3
3300pF
C
C5
3300pF
C
T3
560pF
R
C3
1k
0.22µF
2
24 16 10
9
15
14
20
23
1
28
6
V
OUT5
5V/2A
C
OUT5
220µF
10V
× 2
R
SENSE5
0.05Ω
P-CH
Si9430DY
L2
50µH
D2
MBRS130L
N-CH
Si9410DY
0V = NORMAL
>1.5V = SHDN
0.22µF
C
IN5
22µF
25V
× 2
C
IN3
22µF
25V
× 2
P-CH
Si9430DY
N-CH
Si9410DY
D1
MBRS130L
C
OUT3
220µF
10V
× 2
L1
50µH
R
SENSE3
0.05Ω
V
OUT3
3.3V/2A
V
IN
5.2V TO 18V
R
SENSE3,
R
SENSE5
: DALE WSL-2010-.05
L1, L2: COILTRONICS CTX50-2-MP
PINS 5, 7, 8, 19, 21, 22: NC
1142 F01
NOTE: COMPONENTS OPTIMIZED FOR HIGHEST EFFICIENCY, NOT MINIMUM BOARD SPACE.
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APPLICATIO S
U
FEATURES
TYPICAL APPLICATIO
U
DESCRIPTIO
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Burst Mode is a trademark of Linear Technology Corporation.