LTC1474/LTC1475
Low Quiescent Current
High Efficiency Step-Down
Converters
FEATURES DESCRIPTION
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High Efficiency: Over 92% Possible
The LTC 1474/LTC1475 series are high efficiency step-
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Very Low Standby Current: 10m A Typ
down converters with internal P-channel MOSFET power
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Available in Space Saving 8-Lead MSOP Package
switches that draw only 10m A typical DC supply current at
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Internal 1.4W Power Switch (V = 10V)
no load while maintaining output voltage. The LTC1474
IN
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Wide V Range: 3V to 18V Operation
uses logic-controlled shutdown while the LTC1475 fea-
IN
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Very Low Dropout Operation: 100% Duty Cycle
tures pushbutton on/off.
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Low-Battery Detector Functional During Shutdown
TM
The low supply current coupled with Burst Mode opera-
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Programmable Current Limit with Optional
tion enables the LTC1474/LTC1475 to maintain high effi-
Current Sense Resistor (10mA to 400mA Typ)
ciency over a wide range of loads. These features, along
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Short-Circuit Protection
with their capability of 100% duty cycle for low dropout
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Few External Components Required
and wide input supply range, make the LTC1474/LTC1475
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Active Low Micropower Shutdown: I = 6m A Typ
Q
ideal for moderate current (up to 300mA) battery-powered
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Pushbutton On/Off (LTC1475 Only)
applications.
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3.3V, 5V and Adjustable Output Versions
The peak switch current is user-programmable with an
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optional sense resistor (defaults to 325mA minimum if not
APPLICATIONS
used) providing a simple means for optimizing the design
for lower current applications. The peak current control
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Cellular Telephones and Wireless Modems
also provides short-circuit protection and excellent start-
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4mA to 20mA Current Loop Step-Down Converter
up behavior. A low-battery detector that remains functional
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Portable Instruments
in shutdown is provided .
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Battery-Operated Digital Devices
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Battery Chargers
The LTC1474/LTC1475 series availability in 8-lead MSOP
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Inverting Converters
and SO packages and need for few additional components
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Intrinsic Safety Applications
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.
TYPICAL APPLICATION
LTC1474 Efficiency
100
V
IN
LOW BATTERY OUT
4V TO 18V
V = 5V
IN
+ 90
10F
0.1F V = 10V
IN
7
25V
V
IN
6 1
V
80
OUT
SENSE V V = 15V
FB IN
3.3V AT 250mA
LTC1474-3.3
3 2
L1 +
LOW BATTERY IN LBI LBO
100F
100H
70
6.3V
100k
8 5
RUN SHDN RUN SW
GND
D1
60
L = 100H
4
MBR0530
V = 3.3V
OUT
1474/75 F01
R = 0
L1 = SUMIDA CDRH74-101 SENSE
50
0.03 0.3 3 30 300
Figure 1. High Efficiency Step-Down Converter
LOAD CURRENT (mA)
1474/75 TA01
1
EFFICIENCY (%)
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ULTC1474/LTC1475
ABSOLUTE MAXIMUM RATINGS
Input Supply Voltage (V ).........................0.3V to 20V Operating Ambient Temperature Range
IN
Switch Current (SW, SENSE).............................. 750mA Commercial ............................................ 0 C to 70 C
Switch Voltage (SW) ............. (V 20V) to (V + 0.3V) Industrial ............................................ 40 C to 85 C
IN IN
V (Adjustable Versions) ..........................0.3V to 12V Junction Temperature (Note 1)............................ 125 C
FB
V (Fixed Versions) ................................ 0.3V to 20V Storage Temperature Range ................. 65 C to 150 C
OUT
LBI, LBO ....................................................0.3V to 20V Lead Temperature (Soldering, 10 sec).................. 300 C
RUN, SENSE .................................. 0.3V to (V + 0.3V)
IN
PACKAGE/ORDER INFORMATION
TOP VIEW TOP VIEW
TOP VIEW
TOP VIEW
V /V 1 8 RUN V /V 1 8 ON
OUT FB
OUT FB
V /V 1 8 RUN
OUT FB V /V 1 8 ON
OUT FB
LBO 2 7 V
LBO 2 7 V
LBO 2 7 V IN IN
IN LBO 2 7 V
IN
LBI 3 6 SENSE
LBI/OFF 3 6 SENSE
LBI 3 6 SENSE LBI/OFF 3 6 SENSE
GND 4 5 SW
GND 4 5 SW
GND 4 5 SW GND 4 5 SW
MS8 PACKAGE
MS8 PACKAGE
8-LEAD PLASTIC MSOP 8-LEAD PLASTIC MSOP
S8 PACKAGE S8 PACKAGE
8-LEAD PLASTIC SO 8-LEAD PLASTIC SO
T = 125 C, q = 150 C/ W T = 125 C, q = 150 C/ W T = 125 C, q = 110 C/ W T = 125 C, q = 110 C/ W
JMAX JA JMAX JA JMAX JA JMAX JA
ORDER PART NUMBER ORDER PART NUMBER ORDER PART NUMBER ORDER PART NUMBER
LTC1474CMS8 LTC1475CMS8 LTC1474CS8 LTC1475CS8
LTC1474CMS8-3.3 LTC1475CMS8-3.3 LTC1474IS8 LTC1475IS8
LTC1474CMS8-5 LTC1475CMS8-5 LTC1474CS8-3.3 LTC1475CS8-3.3
LTC1474CS8-5 LTC1475CS8-5
LTC1474IS8-3.3
LTC1474IS8-5
MS8 PART MARKING MS8 PART MARKING S8 PART MARKING S8 PART MARKING
LTBW LTBK 1474 1475
LTCR LTCP 1474I 1475I
LTCS LTCQ 147433 147533
14745 14755
474I33
1474I5
Consult factory for Military grade parts.
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