LTC1142/LTC1142L/LTC1142HV
Dual High Efficiency
Synchronous Step-Down
Switching Regulators
FEATURES
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DESCRIPTIO
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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
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.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a trademark of Linear Technology Corporation.
APPLICATIO S
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Notebook and Palmtop Computers
Battery-Operated Digital Devices
Portable Instruments
DC Power Distribution Systems
TYPICAL APPLICATIO
+
C
IN3
22µF
25V
×
2
V
IN
5.2V TO 18V
0.22µF
P-CH
Si9430DY
23
24
V
IN3
PDRIVE 3
2
SHDN3
0V = NORMAL
>1.5V = SHDN
16
SHDN5
10
V
IN5
PDRIVE 5
9
0.22µF
P-CH
Si9430DY
L2
50µH
V
OUT3
3.3V/2A
R
SENSE3
0.05Ω
L1
50µH
1
1000pF
28
D1
MBRS130L
6
N-CH
Si9410DY
SENSE
+
3
SENSE
–
3
NDRIVE 3
PGND3 SGND3 C
T3
4
3
25
LTC1142HV
SENSE
+
5
SENSE
–
5
NDRIVE 5
15
1000pF
14
20
N-CH
Si9410DY
D2
MBRS130L
+
C
OUT3
220µF
10V
×
2
I
TH3
27
R
C3
1k
I
TH5
13
R
C5
1k
C
T5
11
SGND5 PGND5
17
18
R
SENSE3,
R
SENSE5
: DALE WSL-2010-.05
L1, L2: COILTRONICS CTX50-2-MP
PINS 5, 7, 8, 19, 21, 22: NC
C
T3
C
T5
C
C3
C
C5
560pF 3300pF 3300pF 390pF
1142 F01
NOTE: COMPONENTS OPTIMIZED FOR HIGHEST EFFICIENCY, NOT MINIMUM BOARD SPACE.
Figure 1. High Efficiency Dual 3.3V, 5V Supply
U
+
C
IN5
22µF
25V
×
2
R
SENSE5
0.05Ω
V
OUT5
5V/2A
U
U
+
C
OUT5
220µF
10V
×
2
1
LINER [ LINEAR TECHNOLOGY ]
