LT1121/LT1121-3.3/LT1121-5
Micropower Low Dropout
Regulators with Shutdown
FEATURES DESCRIPTION
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0.4V Dropout Voltage
The LT 1121/LT1121-3.3/LT1121-5 are micropower low
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150mA Output Current
dropout regulators with shutdown. These devices are ca-
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30A Quiescent Current
pable of supplying 150mA of output current with a dropout
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No Protection Diodes Needed
voltage of 0.4V. Designed for use in battery-powered sys-
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Adjustable Output from 3.75V to 30V
tems, the low quiescent current, 30A operating and 16A
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3.3V and 5V Fixed Output Voltages
in shutdown, makes them an ideal choice. The quiescent
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Controlled Quiescent Current in Dropout
current is well-controlled; it does not rise in dropout as it
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Shutdown
does with many other low dropout PNP regulators.
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16A Quiescent Current in Shutdown
Other features of the LT1121/LT1121-3.3/LT1121-5 include
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Stable with 0.33F Output Capacitor
the ability to operate with very small output capacitors.
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Reverse Battery Protection
They are stable with only 0.33F on the output while most
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No Reverse Current with Input Low
older devices require between 1F and 100F for stability.
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Thermal Limiting
Small ceramic capacitors can be used, enhancing manu-
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Available in the 8-Lead SO, 8-Lead PDIP, 3-Lead
facturability. Also the input may be connected to ground
SOT-23 and 3-Lead TO-92 Packages
or a reverse voltage without reverse current flow from
output to input. This makes the LT1121 series ideal for
backup power situations where the output is held high and
APPLICATIONS
the input is at ground or reversed. Under these conditions
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Low Current Regulator
only 16A will flow from the output pin to ground.
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Regulator for Battery-Powered Systems
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
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Post Regulator for Switching Supplies
Technology Corporation. All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
5V Battery-Powered Supply with Shutdown Dropout Voltage
0.5
8 1
3.3V
OUT
IN
OUT
150mA
0.4
+
LT1121-3.3 1F
5V
SOLID TANTALUM
0.3
5
SHDN
GND
0.2
3
0.1
V (PIN 5)
OUTPUT
SHDN
<0.25 OFF
>2.8 ON
0
NC ON
LT1121 TA01
80
0 20 40 60 100 120 140 160
OUTPUT CURRENT (mA)
LT1121 TA02
1121fg
1
DROPOUT VOLTAGE (V)LT1121/LT1121-3.3/LT1121-5
ABSOLUTE MAXIMUM RATINGS
(Note 1)
Input Voltage Output Short-Circuit Duration ....................... Indefinite
LT1121 .............................................................. 30V Operating Junction Temperature Range (Note 3)
LT1121HV ............................................... +36V, 30V LT1121C-X ............................................ 0C to 125C
Output Pin Reverse Current ................................. 10mA LT1121I-X ........................................ 40C to 125C
Adjust Pin Current ................................................ 10mA Storage Temperature Range .................. 65C to 150C
Shutdown Pin Input Voltage (Note 2) .......... 6.5V, 0.6V Lead Temperature (Soldering, 10 sec) ...................300C
Shutdown Pin Input Current (Note 2) .................. 20mA
PIN CONFIGURATION
TOP VIEW
PIN 2 = NC FOR LT1121-3.3/LT1121-5
*
OUT IN FRONT VIEW BOTTOM VIEW
1 8
= ADJ FOR LT1121
PINS 6 AND 7 ARE FLOATING (NO
**
NC/ADJ* 2 7 NC**
3
OUTPUT
INTERNAL CONNECTION) ON THE
GND 3 6 NC** IN GND OUT
STANDARD S8 PACKAGE.
TAB IS
2
GND
PINS 6 AND 7 CONNECTED TO GROUND GND
NC 4 SHDN
5
ON THE A VERSION OF THE LT1121 (S8 ONLY).
CONNECTING PINS 6 AND 7 TO THE
1
V
IN
N8 PACKAGE
GROUND PLANE WILL REDUCE THERMAL
8-LEAD PDIP
RESISTANCE. SEE THERMAL RESISTANCE Z PACKAGE
ST PACKAGE
S8 PACKAGE
TABLES IN THE APPLICATIONS INFORMATION 3-LEAD PLASTIC SOT-223 3-LEAD PLASTIC TO-92
8-LEAD PLASTIC SO
SECTION.
T = 150C, = 50C/W T = 150C, = 150C/W
JMAX JA JMAX JA
T = 150C, = 120C/W (N8, S8)
JMAX JA
T = 150C, = 70C/W (AS8)
JMAX JA
ORDER INFORMATION
LEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE
LT1121CN8#PBF LT1121CN8#TRPBF LT1121CN8 8-Lead Plastic PDIP 0C to 125C
LT1121CN8-3.3#PBF LT1121CN8-3.3#TRPBF LT1121CN8-3.3 8-Lead Plastic PDIP 0C to 125C
LT1121CN8-5#PBF LT1121CN8-5#TRPBF LT1121CN8-5 8-Lead Plastic PDIP 0C to 125C
LT1121IN8#PBF LT1121IN8#TRPBF LT1121IN8 8-Lead Plastic PDIP 40C to 125C
LT1121IN8-3.3#PBF LT1121IN8-3.3#TRPBF LT1121IN8-3.3 8-Lead Plastic PDIP 40C to 125C
LT1121IN8-5#PBF LT1121IN8-5#TRPBF LT1121IN8-5 8-Lead Plastic PDIP 40C to 125C
LT1121CS8#PBF LT1121CS8#TRPBF 1121 8-Lead Plastic S0 0C to 125C
LT1121CS8-3.3#PBF LT1121CS8-3.3#TRPBF 11213 8-Lead Plastic S0 0C to 125C
LT1121CS8-5#PBF LT1121CS8-5#TRPBF 11215 8-Lead Plastic S0 0C to 125C
LT1121HVCS8#PBF LT1121HVCS8#TRPBF 1121HV 8-Lead Plastic S0 40C to 125C
LT1121IS8#PBF LT1121IS8#TRPBF 1121I 8-Lead Plastic S0 40C to 125C
LT1121IS8-3.3#PBF LT1121IS8-3.3#TRPBF 121I3 8-Lead Plastic S0 40C to 125C
LT1121IS8-5#PBF LT1121IS8-5#TRPBF 121I5 8-Lead Plastic S0 40C to 125C
LT1121HVIS8#PBF LT1121HVIS8#TRPBF 121HVI 8-Lead Plastic S0 40C to 125C
LT1121ACS8#PBF LT1121ACS8#TRPBF 1121A 8-Lead Plastic S0 0C to 125C
LT1121ACS8-3.3#PBF LT1121ACS8-3.3#TRPBF 1121A3 8-Lead Plastic S0 0C to 125C
LT1121ACS8-5#PBF LT1121ACS8-5#TRPBF 1121A5 8-Lead Plastic S0 0C to 125C
1121fg
2