LINEAR TECHNOLOGY LT1121, LT1121-3.3, LT1121-5 User Manual

FEATURES

LT1121/LT1121-3.3/LT1121-5

Micropower Low Dropout

Regulators with Shutdown

U

DESCRIPTIO

■

0.4V Dropout Voltage

■

150mA Output Current

■

30µA Quiescent Current

■

No Protection Diodes Needed

■

Adjustable Output from 3.8V to 30V

■

3.3V and 5V Fixed Output Voltages

■

Controlled Quiescent Current in Dropout

■

Shutdown

■

16µA Quiescent Current in Shutdown

■

Stable with 0.33µF Output Capacitor

■

Reverse Battery Protection

■

No Reverse Current with Input Low

■

Thermal Limiting

■

Available in the 8-Lead SO, 8-Lead PDIP, 3-Lead
SOT-23 and 3-Lead TO-92 Packages

U

APPLICATIO S

■

Low Current Regulator

■

Regulator for Battery-Powered Systems

■

Post Regulator for Switching Supplies

The LT®1121/LT1121-3.3/LT1121-5 are micropower low
dropout regulators with shutdown. These devices are
capable of supplying

150mA of output current with a
dropout voltage of 0.4V. Designed for use in battery­powered systems, the low quiescent current, 30µA oper-
ating and 16µA in shutdown, makes them an ideal choice.
The quiescent current is well-controlled; it does not rise in
dropout as it does with many other low dropout PNP
regulators.

Other features of the LT1121/LT1121-3.3/LT1121-5 in­clude the ability to operate with very small output capaci­tors. They are stable with only 0.33µF on the output while
most older devices require between 1µF and 100µF for
stability. Small ceramic capacitors can be used, enhancing
manufacturability. Also the input may be connected to
ground 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 the input is at ground or reversed. Under these
conditions only 16µA will flow from the output pin to
ground.

, LTC and LT are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.

TYPICAL APPLICATIO

5V Battery-Powered Supply with Shutdown

3

OUTPUT

OUT

OFF

ON
ON

1

8

IN

5

V

SHDN

LT1121-3.3

SHDN

GND

(PIN 5)

<0.25

>2.8

NC

5V

U

+

LT1121 • TA01

3.3V

OUT

150mA

1µF
SOLID TANTALUM

Dropout Voltage

0.5

0.4

0.3

0.2

DROPOUT VOLTAGE (V)

0.1

0

0

20 40

OUTPUT CURRENT (mA)

80

60 100 160

120 140

LT1121 • TA02

1121fc

1

LT1121/LT1121-3.3/LT1121-5

WWWU

ABSOLUTE AXI U RATI GS

(Note 1)

Input Voltage

LT1121 ............................................................. ± 30V

LT1121HV ............................................. +36V, – 30V

Output Pin Reverse Current ................................. 10mA

Adjust Pin Current ............................................... 10mA

Shutdown Pin Input Voltage (Note 2) ........ 6.5V, – 0.6V

Shutdown Pin Input Current (Note 2) .................. 20mA

PACKAGE

TOP VIEW

OUT

1

NC/ADJ*

2

GND

3

NC

4

N8 PACKAGE
8-LEAD PDIP

S8 PACKAGE

8-LEAD PLASTIC SO

T

= 150°C, θJA ≈ 120°C/W (N8, S8)

JMAX

= 150°C, θJA ≈ 70°C/W (AS8)

T

JMAX

/

O

RDER I FOR ATIO

PIN 2 = NC FOR LT1121-3.3/LT1121-5

*

IN

8

NC**

7

NC**

6

SHDN

5

= ADJ FOR LT1121
PINS 6 AND 7 ARE FLOATING (NO

**

INTERNAL CONNECTION) ON THE
STANDARD S8 PACKAGE.
PINS 6 AND 7 CONNECTED TO GROUND
ON THE A VERSION OF THE LT1121 (S8 ONLY).
CONNECTING PINS 6 AND 7 TO THE
GROUND PLANE WILL REDUCE THERMAL
RESISTANCE. SEE THERMAL RESISTANCE
TABLES IN THE APPLICATIONS INFORMATION
SECTION.

WU

U

Output Short-Circuit Duration ......................... Indefinite

Operating Junction Temperature Range (Note 3)

LT1121C-X ........................................... 0°C to 125°C

LT1121I-X ....................................... –40°C to 125°C

Storage Temperature Range ................. – 65°C to 150°C

Lead Temperature (Soldering, 10 sec).................. 300°C

FRONT VIEW

TAB IS

GND

ST PACKAGE

3-LEAD PLASTIC SOT-223

= 150°C, θJA ≈ 50°C/W

T

JMAX

3

2

1

OUTPUT

GND

V

IN

BOTTOM VIEW

IN GND OUT

Z PACKAGE

3-LEAD PLASTIC TO-92

T

= 150°C, θJA ≈ 150°C/ W

JMAX

ORDER PART NUMBER

LT1121CN8
LT1121CN8-3.3
LT1121CN8-5
LT1121IN8
LT1121IN8-3.3
LT1121IN8-5
LT1121CS8
LT1121CS8-3.3
LT1121CS8-5
LT1121HVCS8
LT1121IS8

Consult LTC Marketing for parts specified with wider opearating temperature ranges.

LT1121IS8-3.3
LT1121IS8-5
LT1121HVIS8
LT1121ACS8
LT1121ACS8-3.3
LT1121ACS8-5
LT1121AHVCS8
LT1121AIS8
LT1121AIS8-3.3
LT1121AIS8-5
LT1121AHVIS8

S8 PART

MARKING

1121
11213
11215
1121H
1121I
121I3
121I5
121IH

1121A
121A3
121A5
121AH
121AI
121AI3
121AI5
121AIH

ORDER PART

NUMBER

LT1121CST-3.3
LT1121IST-3.3
LT1121CST-5
LT1121IST-5

ORDER PART

NUMBER

LT1121CZ-3.3
LT1121IZ-3.3
LT1121CZ-5
LT1121IZ-5

2

1121fc

LT1121/LT1121-3.3/LT1121-5

ELECTRICAL CHARACTERISTICS

range, otherwise specifications are at T

= 25°C.

A

The ● denotes specifications which apply over the operating temperature

PARAMETER CONDITIONS MIN TYP MAX UNITS

Regulated Output Voltage LT1121-3.3 VIN = 3.8V, I
(Note 4) 4.3V < V

LT1121-5 VIN = 5.5V, I

6V < V

IN

LT1121 (Note 5) VIN = 4.3V, I

4.8V < V

Line Regulation LT1121-3.3 ∆VIN = 4.8V to 20V, I

LT1121-5 ∆VIN = 5.5V to 20V, I
LT1121 (Note 5) ∆VIN = 4.3V to 20V, I

Load Regulation LT1121-3.3 ∆I

LT1121-5 ∆I

LT1121 (Note 5) ∆I

Dropout Voltage I
(Note 6) I

Ground Pin Current I

(Note 7) I

= 1mA, TJ = 25°C 0.13 0.16 V

LOAD

= 1mA ● 0.25 V

LOAD

I

= 50mA, TJ = 25°C 0.30 0.35 V

LOAD

= 50mA ● 0.50 V

LOAD

I

= 100mA, TJ = 25°C 0.37 0.45 V

LOAD

I

= 100mA ● 0.60 V

LOAD

I

= 150mA, TJ = 25°C 0.42 0.55 V

LOAD

= 150mA ● 0.70 V

I

LOAD

= 0mA ● 30 50 µA

LOAD

= 1mA ● 90 120 µA

LOAD

I

= 10mA ● 350 500 µA

LOAD

I

= 50mA ● 1.5 2.5 mA

LOAD

I

= 100mA ● 4.0 7.0 mA

LOAD

I

= 150mA ● 7.0 14.0 mA

LOAD

= 1mA to 150mA, TJ = 25°C–12–25mV

LOAD

= 1mA to 150mA ● –20 –40 mV

∆I

LOAD

= 1mA to 150mA, TJ = 25°C–17–35mV

LOAD

∆I

= 1mA to 150mA ● –28 –50 mV

LOAD

= 1mA to 150mA, TJ = 25°C–12–25mV

LOAD

= 1mA to 150mA ● –18 –40 mV

∆I

LOAD

= 1mA, TJ = 25°C 3.250 3.300 3.350 V

OUT

< 20V, 1mA < I

IN

= 1mA, TJ = 25°C 4.925 5.000 5.075 V

OUT

< 20V, 1mA < I

= 1mA, TJ = 25°C 3.695 3.750 3.805 V

OUT

< 20V, 1mA < I

IN

< 150mA ● 3.200 3.300 3.400 V

OUT

< 150mA ● 4.850 5.000 5.150 V

OUT

< 150mA ● 3.640 3.750 3.860 V

OUT

= 1mA ● 1.5 10 mV

OUT

= 1mA ● 1.5 10 mV

OUT

= 1mA ● 1.5 10 mV

OUT

Adjust Pin Bias Current (Notes 5, 8) TJ = 25°C 150 300 nA

Shutdown Threshold V

Shutdown Pin Current (Note 9) V

Quiescent Current in Shutdown (Note 10) VIN = 6V, V

Ripple Rejection VIN – V

Current Limit VIN – V

Input Reverse Leakage Current VIN = –20V, V

Reverse Output Current (Note 11) LT1121-3.3 V

= Off to On ● 1.2 2.8 V

OUT

V

= On to Off ● 0.25 0.75 V

OUT

= 0V ● 610 µA

SHDN

= 0V ● 15 22 µA

SHDN

= 1V (Avg), V

OUT

f

= 120Hz, I

RIPPLE

OUT

LOAD

= 7V, TJ = 25°C 200 500 mA

= 0V ● 1.0 mA

OUT

LT1121-5 V
LT1121 (Note 5) V

RIPPLE

= 0.5V

,5058dB

P-P

= 0.1A

= 3.3V, VIN = 0V 16 25 µA

OUT

= 5V, VIN = 0V 16 25 µA

OUT

= 3.8V, VIN = 0V 16 25 µA

OUT

Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.

Note 2: The shutdown pin input voltage rating is required for a low
impedance source. Internal protection devices connected to the shutdown
pin will turn on and clamp the pin to approximately 7V or – 0.6V. This
range allows the use of 5V logic devices to drive the pin directly. For high

1121fc

3

LT1121/LT1121-3.3/LT1121-5

ELECTRICAL CHARACTERISTICS

impedance sources or logic running on supply voltages greater than 5.5V,
the maximum current driven into the shutdown pin must be limited to less
than 20mA.

Note 3: For junction temperatures greater than 110°C, a minimum load of
1mA is recommended. For T

> 110°C and I

J

< 1mA, output voltage

OUT

may increase by 1%.
Note 4: Operating conditions are limited by maximum junction

temperature. The regulated output voltage specification will not apply for
all possible combinations of input voltage and output current. When
operating at maximum input voltage, the output current range must be
limited. When operating at maximum output current the input voltage
range must be limited.

Note 5: The LT1121 (adjustable version) is tested and specified with the
adjust pin connected to the output pin.

Note 6: Dropout voltage is the minimum input/output voltage required to
maintain regulation at the specified output current. In dropout the output
voltage will be equal to: (V

Note 7: Ground pin current is tested with VIN = V
current source load. This means that the device is tested while operating
in its dropout region. This is the worst case ground pin current. The
ground pin current will decrease slightly at higher input voltages.

Note 8: Adjust pin bias current flows into the adjust pin.
Note 9: Shutdown pin current at V
Note 10: Quiescent current in shutdown is equal to the sum total of the

shutdown pin current (6µA) and the ground pin current (9µA).
Note 11: Reverse output current is tested with the input pin grounded and

the output pin forced to the rated output voltage. This current flows into
the output pin and out of the ground pin.

UW

TYPICAL PERFOR A CE CHARACTERISTICS

Guaranteed Dropout Voltage

0.7

0.6

0.5

0.4

0.3

0.2

DROPOUT VOLTAGE (V)

0.1
= TEST POINTS

0

0

TJ ≤ 125°C

TJ ≤ 25°C

60

40

20

OUTPUT CURRENT (mA)

80

100

120

140

160

1121 G27

Dropout Voltage

0.7

0.6

I

0.5

0.4

0.3

0.2

DROPOUT VOLTAGE (V)

0.1

0

–50

LLOAD

–25

= 100mA

0

TEMPERATURE (°C)

I

= 150mA

LOAD

I

= 50mA

LOAD

I

= 1mA

LOAD

50

25

75

100

1121 G14

125

– V

IN

DROPOUT

= 0V flows out of the shutdown pin.

SHDN

Quiescent Current

10

VIN = 6V

=

∞

R

LOAD

40

30

20

QUIESCENT CURRENT (µA)

10

0

–50

–25

).

OUT

V

= OPEN

SHDN

V

=0V

SHDN

25

0

TEMPERATURE (°C)

(nominal) and a

50

75

100

1121 G11

125

LT1121-3.3
Quiescent Current

120

100

80

60

40

QUIESCENT CURRENT (µA)

20

0

13579

0

4

V

= OPEN

SHDN

2

4

INPUT VOLTAGE (V)

V

SHDN

6

= 0V

TJ = 25°C

=

R

LOAD

8

1121 G04

LT1121-5
Quiescent Current

120

∞

100

80

V

SHDN

60

40

QUIESCENT CURRENT (µA)

20

10

0

2

13579

0

4

INPUT VOLTAGE (V)

= OPEN

V

SHDN

6

TJ = 25°C

=

R

LOAD

= 0V

8

1121 G02

∞

10

LT1121
Quiescent Current

120

100

80

60

40

QUIESCENT CURRENT (µA)

20

0

2

13579

0

V

= OPEN

SHDN

V

SHDN

6

4

INPUT VOLTAGE (V)

TJ = 25°C
R

LOAD

V

OUT

= 0V

=

∞

= V

ADJ

8

10

1121 G03

1121fc

LT1121/LT1121-3.3/LT1121-5

UW

TYPICAL PERFOR A CE CHARACTERISTICS

LT1121-3.3
Output Voltage

3.38
I

= 1mA

OUT

3.36

3.34

3.32

3.30

3.28

OUTPUT VOLTAGE (V)

3.26

3.24

3.22

–50

–25

LT1121-3.3
Ground Pin Current

800

TJ = 25°C

700

600

500

400

300

200

GROUND PIN CURRENT (µA)

100

0

0

*FOR V

2

13579

50

25

0

TEMPERATURE (°C)

R
I

= 3.3V

OUT

6

4

INPUT VOLTAGE (V)

LOAD

LOAD

R

LOAD

I

LOAD

R
I

LOAD

75

LOAD

100

1121 G22

= 130Ω

= 25mA*

= 330Ω

= 10mA*

= 3.3k

= 1mA*

8

1121 G10

125

10

LT1121-5
Output Voltage

5.08
I

= 1mA

OUT

5.06

5.04

5.02

5.00

4.98

OUTPUT VOLTAGE (V)

4.96

4.94

4.92

–50

–25

LT1121-5
Ground Pin Current

800

TJ = 25°C

700

600

500

400

300

200

GROUND PIN CURRENT (µA)

100

0

2

13579

0

50

25

0

TEMPERATURE (°C)

R

LOAD

I

LOAD

R

LOAD

I

LOAD

*FOR V

INPUT VOLTAGE (V)

= 5V

OUT

R
I

LOAD

6

4

75

LOAD

100

= 200Ω

= 25mA*

= 500Ω

= 10mA*

= 5k

= 1mA*

8

1121 G23

1121 G06

125

LT1121
Adjust Pin Voltage

3.83
I

= 1mA

OUT

3.81

3.79

3.77

3.75

3.73

OUTPUT VOLTAGE (V)

3.71

3.69

3.67

–50

–25

50

25

0

TEMPERATURE (°C)

75

100

125

1121 G24

LT1121
Ground Pin Current

800

TJ = 25°C

= V

V

OUT

700

600

500

400

300

200

GROUND PIN CURRENT (µA)

100

10

0

ADJ

*FOR V

2

13579

0

4

INPUT VOLTAGE (V)

OUT

R
I

R
I

= 3.75V

6

LOAD

LOAD

LOAD

LOAD

R

LOAD

I

LOAD

= 150Ω

= 25mA*

= 380Ω

= 10mA*

= 3.8k

= 1mA*

8

1121 G08

10

LT1121-3.3
Ground Pin Current

10

TJ = 25°C

9

8

7

6

5

4

3

GROUND PIN CURRENT (mA)

2

1

0

2

0

13579

R
I

*FOR V

4

INPUT VOLTAGE (V)

LOAD

LOAD

OUT

= 22Ω

= 150mA*

R

LOAD

I

LOAD

R
I

LOAD

= 3.3V

6

= 33Ω

= 100mA*

= 66Ω

LOAD

= 50mA*

8

1121 G09

LT1121-5
Ground Pin Current

10

TJ = 25°C

9

8

7

6

5

4

3

GROUND PIN CURRENT (mA)

2

1

10

0

2

0

13579

INPUT VOLTAGE (V)

*FOR V

4

OUT

R
I

6

LOAD

LOAD

R
I

LOAD

R
I

LOAD

= 5V

LOAD

LOAD

= 33Ω

= 150mA*

= 50Ω

= 100mA*

= 100Ω

= 50mA*

8

1121 G05

10

LT1121
Ground Pin Current

10

TJ = 25°C

= V

V

9

OUT

ADJ

8

7

6

5

4

3

GROUND PIN CURRENT (mA)

2

1

0

0

13579

*FOR V

2

4

INPUT VOLTAGE (V)

OUT

R

LOAD

I

LOAD

R

LOAD

I

LOAD

R
I

LOAD

= 3.75V

6

= 25Ω

= 150mA*

= 38Ω

= 100mA*

= 75Ω

LOAD

= 50mA*

8

10

1121 G07

1121fc

5