LTC1142/LTC1142L/LTC1142HV
Dual High Efficiency
Synchronous Step-Down
Switching Regulators
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DESCRIPTIO
EATURE
S
F
The LTC®1142/LTC1142L/LTC1142HV are dual synchro-
nous step-down switching regulator controllers featuring
automatic Burst ModeTM 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.
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Dual Outputs: 3.3V and 5V or User Programmable
Ultra-High 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: IQ < 40µA
Wide VIN Range: 3.5V to 20V
Very Low Dropout Operation: 100% Duty Cycle
Synchronous FET Switching for High Efficiency
Available in Standard 28-Pin SSOP
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The operating current level for both regulators is user pro-
grammableviaanexternalcurrentsenseresistor. Wideinput
supply range allows operation from 3.5V* to 18V (20V
maximum).Constantoff-timearchitectureprovideslowdrop-
out regulation limited only by the RDS(ON) of the external
MOSFET and resistance of the inductor and current sense
resistor.
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PPLICATI
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S
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Notebook and Palmtop Computers
Battery-Operated Digital Devices
Portable Instruments
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.
DC Power Distribution Systems
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Modeis a trademark of Linear Technology Corporation.
*For LTC1142L-ADJ only.
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O
TYPICAL APPLICATI
V
IN
5.2V TO 18V
C
IN5
C
+
+
IN3
22µF
25V
× 2
22µF
25V
× 2
0.22µF
0.22µF
0V = NORMAL
>1.5V = SHUTDOWN
2
24
16
10
P-CH
P-CH
Si9430DY
Si9430DY
V
SHUTDOWN 3
V
IN5
SHUTDOWN 5
IN3
23
1
9
L2
L1
50µH
R
R
SENSE5
0.05Ω
SENSE3
PDRIVE 3
PDRIVE 5
50µH
V
0.05Ω
OUT3
3.3V/2A
V
OUT5
5V/2A
15
+
+
SENSE
SENSE
3
SENSE
SENSE
5
5
LTC1142HV
1000pF
1000pF
–
–
3
14
20
28
6
D1
1N5818
D2
NDRIVE 3
PGND3 SGND3
NDRIVE 5
1N5818
N-CH
N-CH
C
C
I
I
SGND5
17
PGND5
18
T5
11
T3
25
TH3
27
TH5
13
C
OUT5
C
+
+
OUT3
Si9410DY
Si9410DY
220µF
4
3
220µF
10V
× 2
10V
× 2
R
C5
1k
R
C3
1k
R
R
: SL-C1-1/2-1R050J
SENSE3, SENSE5
L1, L2: COILTRONICS CTX50-2-MP
PINS 5, 7, 8, 19, 21, 22: NC
C
C
C
C
T5
T3
C3
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
1