LT1521/LT1521-3
LT1521-3.3/LT1521-5
300mA Low Dropout
Regulators with Micropower
Quiescent Current and Shutdown
DESCRIPTIO
FEATURES
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Dropout Voltage: 0.5V The LT 1521/LT1521-3/LT1521-3.3/LT1521-5 are low
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Output Current: 300mA dropout regulators with micropower quiescent current
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Quiescent Current: 12m A and shutdown. These devices are capable of supplying
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No Protection Diodes Needed 300mA of output current with a dropout voltage of 0.5V.
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Adjustable Output from 3.8V to 20V Designed for use in battery-powered systems, the low
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Fixed Output Voltages: 3V, 3.3V, 5V quiescent current, 12m A operating and 6m A in
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Controlled Quiescent Current in Dropout shutdown, makes them an ideal choice. The quiescent
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Shutdown I = 6m A current is well controlled; it does not rise in dropout as it
Q
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Reverse Battery Protection does with many other low dropout PNP regulators.
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No Reverse Current
Other features of the LT1521/LT1521-3/LT1521-3.3/
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Thermal Limiting
LT1521-5 include the ability to operate with very small
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output capacitors. They are stable with only 1.5m F on the
APPLICATIO S
output while most older devices require between 10m F and
100m F for stability. Small ceramic capacitors can be used,
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Low Current Regulator
enhancing manufacturability. Also, the input may be con-
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Regulator for Battery-Powered Systems
nected to voltages lower than the output voltage, including
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Post Regulator for Switching Supplies
negative voltages, without reverse current flow from out-
put to input. This makes the LT1521 series ideal for backup
power situations where the output is held high and the
input is low or reversed. Under these conditions only 5m A
will flow from the output pin to ground.
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO
5V Battery-Powered Supply with Shutdown Dropout Voltage
0.6
5V
8 1
IN OUT
300mA
+ 0.5
6V 1F LT1521-5 1.5F
0.4
5 2
SHDN SENSE
GND
0.3
3
0.2
V (PIN 5) OUTPUT
SHDN
<0.25 OFF 0.1
>2.80 ON
LT1521 TA01
NC ON
0
0 100 150 200 250 300
50
OUTPUT CURRENT (mA)
LT1521 TA02
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DROPOUT VOLTAGE (V)
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ULT1521/LT1521-3
LT1521-3.3/LT1521-5
ABSOLUTE MAXIMUM RATINGS (Note 1)
Input Voltage ...................................................... 20V* Storage Temperature Range ................. 65 C to 150 C
Output Pin Reverse Current .................................. 10mA Operating Junction Temperature Range (Note 2)
Adjust Pin Current ................................................ 10mA Commercial ........................................... 0 C to 125 C
Shutdown Pin Input Voltage (Note 1) ..........6.5V, 0.6V Industrial ......................................... 40 C to 125 C
Shutdown Pin Input Current (Note 1) ..................... 5mA Lead Temperature (Soldering, 10 sec).................. 300 C
Output Short-Circuit Duration .......................... Indefinite
*For applications requiring input voltage ratings greater than 20V, contact
the factory.
PACKAGE/ORDER INFORMATION
TOP VIEW
FRONT VIEW
TOP VIEW
OUT 1 8 IN
3 OUT
OUT 1 8 IN
SENSE/ADJ* 2 7 GND
SENSE/ADJ* 2 7 NC
TAB IS
NC 3 6 NC
2 GND
GND 3 6 GND
GND
GND 4 5 SHDN
NC SHDN
4 5
MS8 PACKAGE 1 IN
8-LEAD PLASTIC MSOP
S8 PACKAGE
ST PACKAGE
8-LEAD PLASTIC SO
*PIN 2 = SENSE FOR LT1521-3/
3-LEAD PLASTIC SOT-223
LT1521-3.3/LT1521-5
*PIN 2 = SENSE FOR LT1521-3/LT1521-3.3/LT1521-5
PIN 2 = ADJ FOR LT1521
= ADJ FOR LT1521
T = 125 C, q = 70 C/ W
T = 125 C, q = 50 C/ W
JMAX JA JMAX JA
T = 125 C, q = 125 C/ W
JMAX JA SEE THE APPLICATIONS INFORMATION SECTION SEE THE APPLICATIONS INFORMATION SECTION
ORDER PART NUMBER
ORDER PART NUMBER ORDER PART NUMBER
LT1521CS8 LT1521CST-3
LT1521CMS8
LT1521CS8-3 LT1521CST-3.3
LT1521CMS8-3
LT1521CS8-3.3 LT1521CST-5
LT1521CMS8-3.3
LT1521CS8-5 LT1521IST-3
LT1521CMS8-5
LT1521IS8 LT1521IST-3.3
LT1521IS8-3 LT1521IST-5
LT1521IS8-3.3
LT1521IS8-5
MS8 PART MARKING
S8 PART MARKING ST PART MARKING
LTEZ
1521 1521I 15213 1521I3
LTFB 15213
1521I3 152133 1521I33
LTDU 152133
1521I33 15215 1521I5
LTFA
15215 1521I5
Consult LTC Marketing for parts specified with wider operating temperature ranges.
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