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LTC1474CS8 Datasheet Download

Part No.:
LTC1474CS8
Download:
Download Datasheet
Description:
[Low Quiescent Current High Efficiency Step-Down Converters]
File Size:
353 K
Page:
20 Pages
Logo:
Manufacturer:
LINER [ LINEAR TECHNOLOGY ]
PCB Prototype
 LTC1474CS8 Datasheet Page:2LTC1474CS8 Datasheet Page:3LTC1474CS8 Datasheet Page:4LTC1474CS8 Datasheet Page:5LTC1474CS8 Datasheet Page:6LTC1474CS8 Datasheet Page:7LTC1474CS8 Datasheet Page:8LTC1474CS8 Datasheet Page:9 
LTC1474/LTC1475
Low Quiescent Current
High Efficiency Step-Down
Converters
DESCRIPTION
The LT C
®
1474/LTC1475 series are high efficiency step-
down converters with internal P-channel MOSFET power
switches that draw only 10µA typical DC supply current at
no load while maintaining output voltage. The LTC1474
uses logic-controlled shutdown while the LTC1475 fea-
tures pushbutton on/off.
The low supply current coupled with Burst Mode
TM
opera-
tion enables the LTC1474/LTC1475 to maintain high effi-
ciency over a wide range of loads. These features, along
with their capability of 100% duty cycle for low dropout
and wide input supply range, make the LTC1474/LTC1475
ideal for moderate current (up to 300mA) battery-powered
applications.
The peak switch current is user-programmable with an
optional sense resistor (defaults to 325mA minimum if not
used) providing a simple means for optimizing the design
for lower current applications. The peak current control
also provides short-circuit protection and excellent start-
up behavior. A low-battery detector that remains functional
in shutdown is provided .
The LTC1474/LTC1475 series availability in 8-lead MSOP
and SO packages and need for few additional components
provide for a minimum area solution.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a trademark of Linear Technology Corporation.
FEATURES
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High Efficiency: Over 92% Possible
Very Low Standby Current: 10
µ
A Typ
Available in Space Saving 8-Lead MSOP Package
Internal 1.4Ω Power Switch (V
IN
= 10V)
Wide V
IN
Range: 3V to 18V Operation
Very Low Dropout Operation: 100% Duty Cycle
Low-Battery Detector Functional During Shutdown
Programmable Current Limit with Optional
Current Sense Resistor (10mA to 400mA Typ)
Short-Circuit Protection
Few External Components Required
Active Low Micropower Shutdown: I
Q
= 6µA Typ
Pushbutton On/Off (LTC1475 Only)
3.3V, 5V and Adjustable Output Versions
APPLICATIONS
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Cellular Telephones and Wireless Modems
4mA to 20mA Current Loop Step-Down Converter
Portable Instruments
Battery-Operated Digital Devices
Battery Chargers
Inverting Converters
Intrinsic Safety Applications
TYPICAL APPLICATION
100
V
IN
4V TO 18V
LOW BATTERY OUT
+
10µF
25V
0.1µF
6
7
V
IN
1
SENSE
V
FB
LTC1474-3.3
3
2
LBI
LBO
8
RUN
SW
5
D1
MBR0530
1474/75 F01
V
OUT
3.3V AT 250mA
L1
100µH
EFFICIENCY (%)
LOW BATTERY IN
RUN SHDN
100k
+
100µF
6.3V
GND
4
L1 = SUMIDA CDRH74-101
Figure 1. High Efficiency Step-Down Converter
U
U
U
LTC1474 Efficiency
90
V
IN
= 5V
V
IN
= 10V
80
V
IN
= 15V
70
60
L = 100µH
V
OUT
= 3.3V
R
SENSE
= 0Ω
0.03
0.3
30
3
LOAD CURRENT (mA)
300
1474/75 TA01
50
1