LTC1159
LTC1159-3.3/LTC1159-5
High Efficiency Synchronous
Step-Down Switching Regulators
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FEATURES
DESCRIPTIO
TheLTC®1159seriesisafamilyofsynchronousstep-down
switching regulator controllers featuring automatic Burst
ModeTM operation to maintain high efficiencies at low
output currents. These devices drive external complemen-
tarypowerMOSFETsatswitchingfrequenciesupto250kHz
using a constant off-time current-mode architecture.
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Operation from 4V to 40V Input Voltage
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Ultrahigh Efficiency: Up to 95%
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20µA Supply Current in Shutdown
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High Efficiency Maintained Over Wide Current Range
Current Mode Operation for Excellent Line and Load
Transient Response
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■
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Very Low Dropout Operation: 100% Duty Cycle
Short-Circuit Protection
Synchronous FET Switching for High Efficiency
Adaptive Non-Overlap Gate Drives
Available in SSOP and SO Packages
A separate pin and on-board switch allow the MOSFET
driver power to be derived from the regulated output
voltageprovidingsignificantefficiencyimprovementwhen
operating at high input voltages. The constant off-time
current-mode architecture maintains constant ripple cur-
rent in the inductor and provides excellent line and load
transient response. The output current level is user pro-
grammable via an external current sense resistor.
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APPLICATIO S
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Step-Down and Inverting Regulators
The LTC1159 automatically switches to power saving
Burst Mode operation when load current drops below
approximately 15% of maximum current. Standby current
is only 300µA while still regulating the output and shut-
down current is a low 20µA.
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Notebook and Palmtop Computers
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Portable Instruments
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Battery-Operated Digital Devices
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Industrial Power Distribution
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Avionics Systems
Telecom Power Supplies
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a trademark of Linear Technology Corporation.
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TYPICAL APPLICATIO
V
IN
+
C
IN
1N4148
100µF
LTC1159-5 Efficiency
V
IN
100V
CAP
P-GATE
Si9435DY
100
90
80
70
60
0.15µF
FIGURE 1 CIRCUIT
V
0.1µF
V
= 10V
+
CC
IN
P-DRIVE
3.3µF
V
CC
EXTV
CC
D1
L*
33µH
R
SENSE
MBRS140T3
V
= 20V
0.05Ω
IN
LTC1159-5
1
2
4
V
OUT
5V/2A
3
+
SHDN1
SHDN2
SENSE
0V = NORMAL
>2V = SHUTDOWN
0.01µF
–
SENSE
I
TH
+
C
OUT
3300pF
1k
C
N-GATE
P-GND
Si9410DY
T
220µF
C
T
S-GND
300pF
*COILTRONICS CTX33-4-MP
0.02
0.2
LOAD CURRENT (A)
2
LTC1159 • F01
LTC1159 • TA01
Figure 1. High Efficiency Step-Down Regulator
1