LTC1159/LTC1159-3.3/LTC1159-5
High Efficiency Synchronous
Step-Down Switching Regulators
FEATURES
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DESCRIPTIO
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Operation from 4V to 40V Input Voltage
Ultra-High Efficiency: Up to 95%
20
µ
A Supply Current in Shutdown
High Efficiency Maintained Over Wide Current Range
Current Mode Operation for Excellent Line and Load
Transient Response
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
The LTC
®
1159 series is a family of synchronous step-down
switching regulator controllers featuring automatic Burst
Mode
TM
operation to maintain high efficiencies at low
output currents. These devices drive external complemen-
tary power MOSFETs at switching frequencies up to 250kHz
using a constant off-time current-mode architecture.
A separate pin and on-board switch allow the MOSFET
driver power to be derived from the regulated output
voltage providing significant efficiency improvement when
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.
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.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a trademark of Linear Technology Corporation.
APPLICATI
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Step-Down and Inverting Regulators
Notebook and Palmtop Computers
Portable Instruments
Battery-Operated Digital Devices
Industrial Power Distribution
Avionics Systems
Telecom Power Supplies
TYPICAL APPLICATI
V
IN
CAP
0.15µF
V
IN
1N4148
P-GATE
0.1µF
P-DRIVE
EXTV
CC
Si9435DY
+
C
IN
100µF
100V
+
3.3µF
V
CC
V
CC
LTC1159-5
0V = NORMAL
>2V = SHUTDOWN
3300pF
1k
C
T
300pF
SHDN1
SHDN2
I
TH
C
T
S-GND
SENSE
+
SENSE
–
N-GATE
P-GND
R
SENSE
0.05Ω
EFFICIENCY (%)
D1
MBRS140T3
L*
33µH
V
OUT
5V/2A
0.01µF
+
Si9410DY
C
OUT
220µF
LTC1159 • F01
*COILTRONICS CTX33-4-MP
Figure 1. High Efficiency Step-Down Regulator
U
LTC1159-5 Efficiency
100
FIGURE 1 CIRCUIT
V
IN
= 10V
90
V
IN
= 20V
80
70
60
0.02
0.2
LOAD CURRENT (A)
2
LTC1159 • TA01
UO
UO
1
LINER [ LINEAR TECHNOLOGY ]
