LTC1771
10µA Quiescent Current
High Efficiency Step-Down
DC/DC Controller
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FEATURES
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DESCRIPTIO
The LTC®1771 is a high efficiency current mode stepdown DC/DC controller that draws as little as 10µA DC
supply current to regulate the output at no load while
maintaining high efficiency for loads up to several amps.
Very Low Standby Current: 10µA
Available in Space-Saving 8-Lead MSOP Package
Output Currents: Up to 5A
Wide VIN Range: 2.8V to 20V Operation
VOUT Range: 1.23V to 18V
High Efficiency: Over 93% Possible
±2% Output Accuracy
Very Low Dropout Operation: 100% Duty Cycle
Current Mode Operation for Excellent Line and
Load Transient Response
Defeatable Burst ModeTM Operation
Short-Circuit Protected
Optional Programmable Soft-Start
Micropower Shutdown: IQ = 2µA
The LTC1771 drives an external P-channel power MOSFET
using a current mode, constant off-time architecture. An
external sense resistor is used to program the operating
current level. Current mode control provides short-circuit
protection, excellent transient response and controlled
start-up behavior. Burst Mode operation enables the
LTC1771 to maintain high efficiency down to extremely
low currents. Shutdown mode further reduces the supply
current to a mere 2µA. For low noise applications, Burst
Mode operation can be easily disabled with the MODE pin.
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Wide input supply range of 2.8V to 18V (20V maximum)
and 100% duty cycle operation for low dropout make the
LTC1771 ideal for a wide variety of battery-powered applications where maximizing battery life is important.
APPLICATIO S
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Cellular Telephones and Wireless Modems
1- to 4-Cell Lithium-Ion-Powered Applications
Portable Instruments
Battery-Powered Equipment
Battery Chargers
Scanners
The LTC1771’s availability in both 8-lead MSOP and SO
packages provides for a minimum area solution.
, 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
VIN
4.5V TO 18V
RSENSE
0.05Ω
LTC1771 Efficiency
+
100
22µF
25V
VIN = 5V
VIN
RUN/SS
CSS
0.01µF
SENSE
PGATE
M1
Si6447DQ
ITH LTC1771
RC
10k
CC
22OpF
VFB
MODE
GND
VIN
L1
15µH
UPS5817
R2
1.64M
1%
+
COUT
150µF
6.3V
VOUT
3.3V
2A
EFFICIENCY (%)
90
80
VIN = 10V
VIN = 15V
70
60
50
R1
1M
1%
CFF
5pF
Figure 1. High Efficiency Step-Down Converter
1771 F01
VOUT = 3.3V
RSENSE = 0.05Ω
40
10
0.1
1
100
1000
LOAD CURRENT (mA)
10000
1771 F01b
1