LTC1142 Datasheet, PDF (1/20 Pages) Linear Technology – Dual High Efficiency Synchronous Step-Down Switching Regulators

FEATURES
s _{Dual Outputs: 3.3V and 5V or User Programmable}
s _{Ultra-High Efficiency: Over 95% Possible}
s _{Current Mode Operation for Excellent Line and Load}
Transient Response
s _{High Efficiency Maintained over 3 Decades of}
Output Current
s _{Low Standby Current at Light Loads: 160µA/Output}
s _{Independent Micropower Shutdown: IQ < 40µA}
s _{Wide VIN Range: 3.5V to 20V}
s _{Very Low Dropout Operation: 100% Duty Cycle}
s _{Synchronous FET Switching for High Efficiency}
s _{Available in Standard 28-Pin SSOP}
APPLICATI S
s _{Notebook and Palmtop Computers}
s _{Battery-Operated Digital Devices}
s _{Portable Instruments}
s _{DC Power Distribution Systems}
LTC1142/LTC1142L/LTC1142HV
Dual High Efficiency
Synchronous Step-Down
Switching Regulators
DESCRIPTIO
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.
*For LTC1142L-ADJ only.
TYPICAL APPLICATI
V_IN
5.2V TO 18V
V_OUT3
3.3V/2A
R_SENSE3
0.05Ω
C_IN3
22µF
25V
×2
L1
50µH
0.22µF
P-CH
Si9430DY
24
V_IN3
23
PDRIVE 3
0V = NORMAL
>1.5V = SHUTDOWN
2
16
SHUTDOWN 3
SHUTDOWN 5
0.22µF
10
V_IN5
9
PDRIVE 5
P-CH
Si9430DY
1000pF
1 _{SENSE+ 3}
LTC1142HV
SENSE⁺ 5 ¹⁵
1000pF
D1
1N5818
C_OUT3
220µF
10V
×2
N-CH
Si9410DY
SENSE^– 3
28
NDRIVE 3
6
PGND3 SGND3 C_T3
4
3 25
SENSE^– 5
14
NDRIVE 5
20
I_TH3 I_TH5 C_T5 SGND5 PGND5
27
13 11
17 18
R_C3 R_C5
1k
1k
N-CH
Si9410DY
R_SENSE3, R_SENSE5 : SL-C1-1/2-1R050J
L1, L2: COILTRONICS CTX50-2-MP
PINS 5, 7, 8, 19, 21, 22: NC
C_T3 C_C3 C_C5 C_T5
560pF 3300pF 3300pF 390pF
NOTE: COMPONENTS OPTIMIZED FOR HIGHEST EFFICIENCY, NOT MINIMUM BOARD SPACE.
Figure 1. High Efficiency Dual 3.3V, 5V
+
C_IN5
22µF
25V
×2
L2
50µH
R_SENSE5
0.05Ω
V_OUT5
5V/2A
D2
1N5818
+ ^COUT5
220µF
10V
×2
1142 F01
1