ANALOG DEVICES LT 1761 ES5-5 Datasheet

LT1761 Series

100mA, Low Noise,

LDO Micropower

Regulators in TSOT-23

FEATURES

n

Low Noise: 20μV

n

Low Quiescent Current: 20μA

n

Wide Input Voltage Range: 1.8V to 20V

n

Output Current: 100mA

n

Very Low Shutdown Current: <0.1μA

n

Low Dropout Voltage: 300mV at 100mA

n

Fixed Output Voltages: 1.2V, 1.5V, 1.8V, 2V, 2.5V,

(10Hz to 100kHz)

RMS

2.8V, 3V, 3.3V, 5V

n

Adjustable Output from 1.22V to 20V

n

Stable with 1μF Output Capacitor

n

Stable with Aluminum, Tantalum or

Ceramic Capacitors

n

Reverse-Battery Protected

n

No Reverse Current

n

No Protection Diodes Needed

n

Overcurrent and Overtemperature Protected

n

Available in Tiny 5-Lead TSOT-23 Package

APPLICATIONS

n

Cellular Phones

n

Pagers

n

Battery-Powered Systems

n

Frequency Synthesizers

n

Wireless Modems

DESCRIPTION

The LT®1761 series are micropower, low noise, low
dropout regulators. With an external 0.01μF bypass
capacitor, output noise drops to 20μV
100kHz bandwidth. Designed for use in battery-powered
systems, the low 20μA quiescent current makes them an
ideal choice. In shutdown, quiescent current drops to less
than 0.1μA. The devices are capable of operating over an
input voltage from 1.8V to 20V, and can supply 100mA of
output current with a dropout voltage of 300mV. Quiescent
current is well controlled, not rising in dropout as it does
with many other regulators.

The LT1761 regulators are stable with output capacitors as
low as 1μF. Small ceramic capacitors can be used without
the series resistance required by other regulators.

Internal protection circuitry includes reverse battery
protection, current limiting, thermal limiting and reverse
current protection. The device is available in fi xed output
voltages of 1.2V, 1.5V, 1.8V, 2V, 2.5V, 2.8V, 3V, 3.3V and
5V, and as an adjustable device with a 1.22V reference
voltage. The LT1761 regulators are available in the 5-lead
TSOT-23 package.

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

over a 10Hz to

RMS

TYPICAL APPLICATION

5V Low Noise Regulator

V

5.4V TO
20V

IN

1μF

IN

SHDN

OUT

LT1761-5

BYP

GND

0.01μF

+

5V AT100mA
20μV

10μF

1761 TA01

RMS

NOISE

V

OUT

100μV/DIV

10Hz to 100kHz Output Noise

1761 TA01b

20μV

RMS

1761sfe

1

LT1761 Series

ABSOLUTE MAXIMUM RATINGS

IN Pin Voltage .........................................................±20V

OUT Pin Voltage ......................................................±20V

Input to Output Differential Voltage .........................±20V

ADJ Pin Voltage ...................................................... ±7V

BYP Pin Voltage .....................................................±0.6V

SHDN Pin Voltage ................................................. ±20V

(Note 1)

Output Short-Circuit Duration ........................ Indefi nite

Operating Junction Temperature Range

E, I Grade (Note 2) ............................. –40°C to 125°C

MP Grade (Note 2) ............................. –55°C to 125°C

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

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

PIN CONFIGURATION

LT1761-BYP LT1761-SD LT1761-X

GND 2

BYP 3

SEE APPLICATIONS INFORMATION SECTION

TOP VIEW

IN 1

S5 PACKAGE

5-LEAD PLASTIC TSOT-23

T

= 150°C, θJA = 250°C/W

JMAX

5 OUT

4 ADJ

TOP VIEW

IN 1

GND 2

SHDN 3

S5 PACKAGE

5-LEAD PLASTIC TSOT-23

T

= 150°C, θJA = 250°C/W

JMAX

SEE APPLICATIONS INFORMATION SECTION

5 OUT

4 ADJ

TOP VIEW

IN 1

GND 2

SHDN 3

S5 PACKAGE

5-LEAD PLASTIC TSOT-23

T

= 150°C, θJA = 250°C/W

JMAX

SEE APPLICATIONS INFORMATION SECTION

5 OUT

4 BYP

2

1761sfe

LT1761 Series

ORDER INFORMATION

LEAD FREE FINISH TAPE AND REEL PART MARKING * PACKAGE DESCRIPTION TEMPERATURE RANGE

LT1761ES5-BYP#PBF LT1761ES5-BYP#TRPBF LTGC 5-Lead Plastic TSOT-23 –40°C to 125°C
LT1761IS5-BYP#PBF LT1761IS5-BYP#TRPBF LTGC 5-Lead Plastic TSOT-23 –40°C to 125°C
LT1761ES5-SD#PBF LT1761ES5-SD#TRPBF LTGH 5-Lead Plastic TSOT-23 –40°C to 125°C
LT1761IS5-SD#PBF LT1761IS5-SD#TRPBF LTGH 5-Lead Plastic TSOT-23 –40°C to 125°C
LT1761ES5-1.2#PBF LT1761ES5-1.2#TRPBF LTCDS 5-Lead Plastic TSOT-23 –40°C to 125°C
LT1761IS5-1.2#PBF LT1761IS5-1.2#TRPBF LTCDS 5-Lead Plastic TSOT-23 –40°C to 125°C
LT1761ES5-1.5#PBF LT1761ES5-1.5#TRPBF LTMT 5-Lead Plastic TSOT-23 –40°C to 125°C
LT1761IS5-1.5#PBF LT1761IS5-1.5#TRPBF LTMT 5-Lead Plastic TSOT-23 –40°C to 125°C
LT1761ES5-1.8#PBF LT1761ES5-1.8#TRPBF LTJM 5-Lead Plastic TSOT-23 –40°C to 125°C
LT1761IS5-1.8#PBF LT1761IS5-1.8#TRPBF LTJM 5-Lead Plastic TSOT-23 –40°C to 125°C
LT1761MPS5-1.8#PBF LT1761MPS5-1.8#TRPBF LTDCH 5-Lead Plastic TSOT-23 –55°C to 125°C
LT1761ES5-2#PBF LT1761ES5-2#TRPBF LTJE 5-Lead Plastic TSOT-23 –40°C to 125°C
LT1761IS5-2#PBF LT1761IS5-2#TRPBF LTJE 5-Lead Plastic TSOT-23 –40°C to 125°C
LT1761ES5-2.5#PBF LT1761ES5-2.5#TRPBF LTGD 5-Lead Plastic TSOT-23 –40°C to 125°C
LT1761IS5-2.5#PBF LT1761IS5-2.5#TRPBF LTGD 5-Lead Plastic TSOT-23 –40°C to 125°C
LT1761ES5-2.8#PBF LT1761ES5-2.8#TRPBF LTLB 5-Lead Plastic TSOT-23 –40°C to 125°C
LT1761IS5-2.8#PBF LT1761IS5-2.8#TRPBF LTLB 5-Lead Plastic TSOT-23 –40°C to 125°C
LT1761ES5-3#PBF LT1761ES5-3#TRPBF LTGE 5-Lead Plastic TSOT-23 –40°C to 125°C
LT1761IS5-3#PBF LT1761IS5-3#TRPBF LTGE 5-Lead Plastic TSOT-23 –40°C to 125°C
LT1761ES5-3.3#PBF LT1761ES5-3.3#TRPBF LTGF 5-Lead Plastic TSOT-23 –40°C to 125°C
LT1761IS5-3.3#PBF LT1761IS5-3.3#TRPBF LTGF 5-Lead Plastic TSOT-23 –40°C to 125°C
LT1761ES5-5#PBF LT1761ES5-5#TRPBF LTGG 5-Lead Plastic TSOT-23 –40°C to 125°C
LT1761IS5-5#PBF LT1761IS5-5#TRPBF LTGG 5-Lead Plastic TSOT-23 –40°C to 125°C

LEAD BASED FINISH TAPE AND REEL PART MARKING * PACKAGE DESCRIPTION TEMPERATURE RANGE

LT1761ES5-BYP LT1761ES5-BYP#TR LTGC 5-Lead Plastic TSOT-23 –40°C to 125°C
LT1761IS5-BYP LT1761IS5-BYP#TR LTGC 5-Lead Plastic TSOT-23 –40°C to 125°C
LT1761ES5-SD LT1761ES5-SD#TR LTGH 5-Lead Plastic TSOT-23 –40°C to 125°C
LT1761IS5-SD LT1761IS5-SD#TR LTGH 5-Lead Plastic TSOT-23 –40°C to 125°C
LT1761ES5-1.2 LT1761ES5-1.2#TR LTCDS 5-Lead Plastic TSOT-23 –40°C to 125°C
LT1761IS5-1.2 LT1761IS5-1.2#TR LTCDS 5-Lead Plastic TSOT-23 –40°C to 125°C
LT1761ES5-1.5 LT1761ES5-1.5#TR LTMT 5-Lead Plastic TSOT-23 –40°C to 125°C
LT1761IS5-1.5 LT1761IS5-1.5#TR LTMT 5-Lead Plastic TSOT-23 –40°C to 125°C
LT1761ES5-1.8 LT1761ES5-1.8#TR LTJM 5-Lead Plastic TSOT-23 –40°C to 125°C
LT1761IS5-1.8 LT1761IS5-1.8#TR LTJM 5-Lead Plastic TSOT-23 –40°C to 125°C
LT1761MPS5-1.8 LT1761MPS5-1.8#TR LTDCH 5-Lead Plastic TSOT-23 –55°C to 125°C
LT1761ES5-2 LT1761ES5-2#TR LTJE 5-Lead Plastic TSOT-23 –40°C to 125°C
LT1761IS5-2 LT1761IS5-2#TR LTJE 5-Lead Plastic TSOT-23 –40°C to 125°C
LT1761ES5-2.5 LT1761ES5-2.5#TR LTGD 5-Lead Plastic TSOT-23 –40°C to 125°C
LT1761IS5-2.5 LT1761IS5-2.5#TR LTGD 5-Lead Plastic TSOT-23 –40°C to 125°C
LT1761ES5-2.8 LT1761ES5-2.8#TR LTLB 5-Lead Plastic TSOT-23 –40°C to 125°C
LT1761IS5-2.8 LT1761IS5-2.8#TR LTLB 5-Lead Plastic TSOT-23 –40°C to 125°C
LT1761ES5-3 LT1761ES5-3#TR LTGE 5-Lead Plastic TSOT-23 –40°C to 125°C
LT1761IS5-3 LT1761IS5-3#TR LTGE 5-Lead Plastic TSOT-23 –40°C to 125°C
LT1761ES5-3.3 LT1761ES5-3.3#TR LTGF 5-Lead Plastic TSOT-23 –40°C to 125°C
LT1761IS5-3.3 LT1761IS5-3.3#TR LTGF 5-Lead Plastic TSOT-23 –40°C to 125°C
LT1761ES5-5 LT1761ES5-5#TR LTGG 5-Lead Plastic TSOT-23 –40°C to 125°C
LT1761IS5-5 LT1761IS5-5#TR LTGG 5-Lead Plastic TSOT-23 –40°C to 125°C
Consult LTC Marketing for parts specifi ed with wider operating temperature ranges. *The temperature grade is identifi ed by a label on the shipping container.

For more information on lead free part marking, go to:
For more information on tape and reel specifi cations, go to:

http://www.linear.com/leadfree/

http://www.linear.com/tapeandreel/

1761sfe

3

LT1761 Series

ELECTRICAL CHARACTERISTICS

The l denotes the specifi cations which apply over the full operating
temperature range, otherwise specifi cations are at T

PARAMETER CONDITIONS MIN TYP MAX UNITS

Minimum Input Voltage (Notes 3, 11) I
Regulated Output Voltage (Note 4) LT1761-1.2 V

ADJ Pin Voltage (Note 3, 4) LT1761 V

Line Regulation LT1761-1.2

= 100mA

LOAD

LT1761-1.5 V

LT1761-1.8 VIN = 2.3V, I

LT1761-2 V

LT1761-2.5 V

LT1761-2.8 V

LT1761-3 V

LT1761-3.3 V

LT1761-5 V

LT1761-1.5
LT1761-1.8
LT1761-2
LT1761-2.5
LT1761-2.8
LT1761-3
LT1761-3.3
LT1761-5
LT1761 (Note 3)

= 25°C. (Note 2)

A

= 2V, I

IN

2.3V < V

2.3V < V
= 2V, I

IN

2.5V < V

2.5V < V

2.8V < V

2.8V < V
= 2.5V, I

IN

3V < V
3V < V

= 3V, I

IN

3.5V < V

3.5V < V
= 3.3V, I

IN

3.8V < V

3.8V < V
= 3.5V, I

IN

4V < V
4V < V

= 3.8V, I

IN

4.3V < V

4.3V < V
= 5.5V, I

IN

6V < V
6V < V

= 2V, I

IN

2.3V < V

2.3V < V

ΔV

= 2V to 20V, I

IN

ΔV

= 2V to 20V, I

IN

ΔV

= 2.3V to 20V, I

IN

ΔV

= 2.5V to 20V, I

IN

ΔV

= 3V to 20V, I

IN

ΔV

= 3.3V to 20V, I

IN

ΔV

= 3.5V to 20V, I

IN

ΔV

= 3.8V to 20V, I

IN

ΔV

= 5.5V to 20V, I

IN

ΔV

= 2V to 20V, I

IN

= 1mA

LOAD

< 20V, 1mA < I

IN

< 20V, 1mA < I

IN

= 1mA

LOAD

< 20V, 1mA < I

IN

< 20V, 1mA < I

IN

LOAD

< 20V, 1mA < I

IN

< 20V, 1mA < I

IN

LOAD

< 20V, 1mA < I

IN

< 20V, 1mA < I

IN

= 1mA

LOAD

< 20V, 1mA < I

IN

< 20V, 1mA < I

IN

LOAD

< 20V, 1mA < I

IN

< 20V, 1mA < I

IN

LOAD

< 20V, 1mA < I

IN

< 20V, 1mA < I

IN

LOAD

< 20V, 1mA < I

IN

< 20V, 1mA < I

IN

LOAD

< 20V, 1mA < I

IN

< 20V, 1mA < I

IN

= 1mA

LOAD

< 20V, 1mA < I

IN

< 20V, 1mA < I

IN

= 1mA

= 1mA

= 1mA

= 1mA

= 1mA

= 1mA

LOAD
LOAD

LOAD
LOAD

LOAD

LOAD
LOAD
LOAD
LOAD

LOAD

LOAD
LOAD

LOAD
LOAD

LOAD
LOAD

< 50mA

LOAD

< 100mA

LOAD

LOAD
LOAD

LOAD
LOAD

< 50mA

LOAD

< 100mA

LOAD

LOAD
LOAD

< 50mA

LOAD

< 100mA

LOAD

LOAD
LOAD

= 1mA
= 1mA

= 1mA
= 1mA

= 1mA

= 1mA
= 1mA
= 1mA
= 1mA

= 1mA

< 50mA
< 100mA

< 50mA
< 100mA

< 50mA
< 100mA

< 50mA
< 100mA

< 50mA
< 100mA

< 50mA
< 100mA

< 50mA
< 100mA

l

1.185

l

1.170

l

1.150

1.478

l

1.457

l

1.436

1.775

l

1.750

l

1.725

1.970

l

1.945

l

1.920

2.465

l

2.435

l

2.415

2.762

l

2.732

l

2.706

2.960

l

2.930

l

2.900

3.250

l

3.230

l

3.190

4.935

l

4.900

l

4.850

1.205

l

1.190

l

1.170

l
l
l
l
l
l
l
l
l
l

1.8 2.3 V

1.2

1.2

1.2

1.5

1.5

1.5

1.8

1.8

1.8

2.5

2.5

2.5

2.8

2.8

2.8

3.3

3.3

3.3

1.220

1.220

1.220

1.215

1.230

1.240

1.522

1.538

1.555

1.825

1.845

1.860

2

2.030

2

2.045

2

2.060

2.535

2.565

2.575

2.838

2.868

2.884

3

3.040

3

3.070

3

3.090

3.350

3.370

3.400

5

5.065

5

5.100

5

5.120

1.235

1.250

1.260

1
1
1
1
1
1
1
1
1
1

10
10
10
10
10
10
10
10
10
10

mV
mV
mV
mV
mV
mV
mV
mV
mV
mV

V
V
V

V
V
V

V
V
V

V
V
V

V
V
V

V
V
V

V
V
V

V
V
V

V
V
V

V
V
V

4

1761sfe

LT1761 Series

ELECTRICAL CHARACTERISTICS

The l denotes the specifi cations which apply over the full operating
temperature range, otherwise specifi cations are at T

PARAMETER CONDITIONS MIN TYP MAX UNITS

Load Regulation

Dropout Voltage
V

= V

IN

OUT(NOMINAL)

(Notes 5, 6, 11)

LT1761-1.2

LT1761-1.5

LT1761-1.8

LT1761-2

LT1761-2.5

LT1761-2.8

LT1761-3

LT1761-3.3

LT1761-5

LT1761 (Note 3)

= 1mA

I

LOAD

I

= 1mA

LOAD

I

= 10mA

LOAD

I

= 10mA

LOAD

I

= 50mA

LOAD

I

= 50mA

LOAD

I

= 100mA

LOAD

I

= 100mA

LOAD

= 25°C. (Note 2)

A

VIN = 2.3V, ΔI
V

= 2.3V, ΔI

IN

V

= 2.3V, ΔI

IN

V

= 2.3V, ΔI

IN

V

= 2.5V, ΔI

IN

V

= 2.5V, ΔI

IN

V

= 2.5V, ΔI

IN

V

= 2.5V, ΔI

IN

V

= 2.8V, ΔI

IN

V

= 2.8V, ΔI

IN

V

= 2.8V, ΔI

IN

V

= 2.8V, ΔI

IN

V

= 3V, ΔI

IN

V

= 3V, ΔI

IN

V

= 3V, ΔI

IN

V

= 3V, ΔI

IN

V

= 3.5V, ΔI

IN

V

= 3.5V, ΔI

IN

V

= 3.5V, ΔI

IN

V

= 3.5V, ΔI

IN

V

= 3.8V, ΔI

IN

V

= 3.8V, ΔI

IN

V

= 3.8V, ΔI

IN

V

= 3.8V, ΔI

IN

V

= 4V, ΔI

IN

V

= 4V, ΔI

IN

V

= 4V, ΔI

IN

V

= 4V, ΔI

IN

V

= 4.3V, ΔI

IN

V

= 4.3V, ΔI

IN

V

= 4.3V, ΔI

IN

V

= 4.3V, ΔI

IN

V

= 6V, ΔI

IN

V

= 6V, ΔI

IN

VIN = 6V, ΔI
V

= 6V, ΔI

IN

V

= 2.3V, ΔI

IN

VIN = 2.3V, ΔI
V

= 2.3V, ΔI

IN

V

= 2.3V, ΔI

IN

LOAD
LOAD
LOAD
LOAD

LOAD
LOAD
LOAD
LOAD

LOAD
LOAD
LOAD
LOAD

LOAD
LOAD
LOAD
LOAD

LOAD
LOAD
LOAD
LOAD

LOAD
LOAD
LOAD
LOAD

LOAD
LOAD
LOAD
LOAD

LOAD
LOAD
LOAD
LOAD

LOAD
LOAD
LOAD
LOAD

LOAD
LOAD
LOAD
LOAD

= 1mA to 50mA
= 1mA to 50mA
= 1mA to 100mA
= 1mA to 100mA

= 1mA to 50mA
= 1mA to 50mA
= 1mA to 100mA
= 1mA to 100mA

= 1mA to 50mA
= 1mA to 50mA
= 1mA to 100mA
= 1mA to 100mA

= 1mA to 50mA
= 1mA to 50mA
= 1mA to 100mA
= 1mA to 100mA

= 1mA to 50mA
= 1mA to 50mA
= 1mA to 100mA
= 1mA to 100mA

= 1mA to 50mA
= 1mA to 50mA
= 1mA to 100mA
= 1mA to 100mA

= 1mA to 50mA
= 1mA to 50mA
= 1mA to 100mA
= 1mA to 100mA

= 1mA to 50mA
= 1mA to 50mA
= 1mA to 100mA
= 1mA to 100mA

= 1mA to 50mA
= 1mA to 50mA
= 1mA to 100mA
= 1mA to 100mA

= 1mA to 50mA
= 1mA to 50mA
= 1mA to 100mA
= 1mA to 100mA

l

1

1

l

10

l

14

l

10

l

15

l

10

l

15

l

10

l

20

l

10

l

20

l

10

l

20

l

10

l

20

l

15

l

25

l

1

l

1

l

6
12
12
50

20
35
30
55

20
35
30
60

20
35
35
65

20
35
40
80

20
38
40
86

20
40
40
90

20
40
40

100

30
60
65

150

6
12
12
50

mV
mV
mV
mV

mV
mV
mV
mV

mV
mV
mV
mV

mV
mV
mV
mV

mV
mV
mV
mV

mV
mV
mV
mV

mV
mV
mV
mV

mV
mV
mV
mV

mV
mV
mV
mV

mV
mV
mV
mV

0.10 0.15

l

0.19

0.17 0.22

l

0.29

0.24 0.28

l

0.38

0.30 0.35

0.45

V
V

V
V

V
V

V
V

1761sfe

5

LT1761 Series

ELECTRICAL CHARACTERISTICS

The l denotes the specifi cations which apply over the full operating
temperature range, otherwise specifi cations are at T

PARAMETER CONDITIONS MIN TYP MAX UNITS

GND Pin Current
V

= V

IN

OUT(NOMINAL)

(Notes 5, 7)

Output Voltage Noise C
ADJ Pin Bias Current (Notes 3, 8) 30 100 nA
Shutdown Threshold V

SHDN Pin Current
(Note 9)

Quiescent Current in Shutdown VIN = 6V, V
Ripple Rejection (Note 3) V

Current Limit V

Input Reverse Leakage Current V
Reverse Output Current

(Note 10)

= 0mA

I

LOAD

I

= 1mA

LOAD

I

= 10mA

LOAD

I

= 50mA

LOAD

I

= 100mA

LOAD

= 10μF, C

OUT

= Off to On

OUT

V

= On to Off

OUT

= 0V

V

SHDN

V

= 20V

SHDN

SHDN

– V

IN

I

LOAD

IN

V

IN

IN

= 1.5V (Avg), V

OUT

= 50mA

= 7V, V

OUT

= V

OUT(NOMINAL)

= –20V, V

LT1761-1.2
LT1761-1.5
LT1761-1.8
LT1761-2
LT1761-2.5
LT1761-2.8
LT1761-3
LT1761-3.3
LT1761-5
LT1761 (Note 3)

= 25°C. (Note 2)

A

= 0.01μF, I

BYP

l
l
l
l
l

= 100mA, BW = 10Hz to 100kHz 20 μV

LOAD

l
l

0.25

l
l

20
55

230

1

2.2

0.8

0.65
0

1

45
100
400

2
4

2V

0.5
3

= 0V 0.01 0.1 μA

RIPPLE

= 0V

+ 1V or 2.3V (Note 12), ΔV

= 0V

OUT

V

= 1.2V, VIN < 1.2V

OUT

V

= 1.5V, VIN < 1.5V

OUT

V

= 1.8V, VIN < 1.8V

OUT

V

= 2V, VIN < 2V

OUT

V

= 2.5V, VIN < 2.5V

OUT

V

= 2.8V, VIN < 2.8V

OUT

V

= 3V, VIN < 3V

OUT

V

= 3.3V, VIN < 3.3V

OUT

V

= 5V, VIN < 5V

OUT

V

= 1.22V, VIN < 1.22V

OUT

= 0.5V

P-P

, f

RIPPLE

= 120Hz,

= –5%

OUT

55 65 dB

200 mA

l

110

l

10
10
10
10
10
10
10
10
10

5

1mA

20
20
20
20
20
20
20
20
20
10

μA
μA

μA
mA
mA

RMS

μA

μA

mA

μA

μA

μA

μA

μA

μA

μA

μA

μA

μA

V

Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.

Note 2: The LT1761 regulators are tested and specifi ed under pulse load
conditions such that T
at T

= 25°C. Performance at –40°C and 125°C is assured by design,

A

≈ TA. The LT1761E is 100% production tested

J

characterization and correlation with statistical process controls. The
LT1761I is guaranteed over the full –40°C to 125°C operating junction
temperature range. The LT1761MP is 100% tested and guaranteed over
the –55°C to 125°C operating junction temperature range.

Note 3: The LT1761 (adjustable versions) are tested and specifi ed for
these conditions with the ADJ pin connected to the OUT pin.

Note 4: Operating conditions are limited by maximum junction
temperature. The regulated output voltage specifi cation 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: To satisfy requirements for minimum input voltage, the LT1761
(adjustable version) is tested and specifi ed for these conditions with an
external resistor divider (two 250k resistors) for an output voltage of

2.44V. The external resistor divider will add a 5μA DC load on the output.

Note 6: Dropout voltage is the minimum input to output voltage differential
needed to maintain regulation at a specifi ed output current. In dropout, the
output voltage will be equal to: V

Note 7: GND pin current is tested with V

IN

– V

DROPOUT

= V

IN

.

OUT(NOMINAL)

or VIN = 2.3V
(whichever is greater) and a current source load. This means the device
is tested while operating in its dropout region or at the minimum input
voltage specifi cation. This is the worst-case GND pin current. The GND pin
current will decrease slightly at higher input voltages.

Note 8: ADJ pin bias current fl ows into the ADJ pin.
Note 9: SHDN pin current fl ows into the SHDN pin.
Note 10: Reverse output current is tested with the IN pin grounded and the

OUT pin forced to the rated output voltage. This current fl ows into the OUT
pin and out the GND pin.

Note 11: For the LT1761, LT1761-1.2, LT1761-1.5, LT1761-1.8 and
LT1761-2 dropout voltage will be limited by the minimum input voltage
specifi cation under some output voltage/load conditions. See the curve of
Minimum Input Voltage in the Typical Performance Characteristics.

Note 12: To satisfy requirements for minimum input voltage, current limit
is tested at V

= V

IN

OUT(NOMINAL)

+ 1V or VIN = 2.3V, whichever is greater.

1761sfe

6

TYPICAL PERFORMANCE CHARACTERISTICS

Typical Dropout Voltage Guaranteed Dropout Voltage Dropout Voltage

500

450

400

350

300

250

200

150

DROPOUT VOLTAGE (mV)

100

50

0

0 102030

TJ = 125°C

TJ = 25°C

40

60 70 80 90 100

50

OUTPUT CURRENT (mA)

1761 G00

500

450

400

350

300

250

200

150

DROPOUT VOLTAGE (mV)

100

50

0

0 102030

= TEST POINTS

40

OUTPUT CURRENT (mA)

TJ ≤ 125°C

TJ ≤ 25°C

60 70 80 90 100

50

1761 G01

500

450

400

350

300

250

200

150

DROPOUT VOLTAGE (mV)

100

50

0

–50

LT1761 Series

IL = 100mA

IL = 50mA

IL = 10mA

IL = 1mA

50

25

–25

0

TEMPERATURE (°C)

75

100

125

1761 G01.1

Quiescent Current

40

VIN = 6V

= ∞ (250k FOR LT1761-BYP, -SD)

R

L

35

= 0 (5μA FOR LT1761-BYP, -SD)

I

L

30

25

20

15

10

QUIESCENT CURRENT (μA)

5

0

–50

V

SHDN

V

050

–25 25 75 125

TEMPERATURE (°C)

LT1761-1.8
Output Voltage

1.84
IL = 1mA

1.83

1.82

1.81

1.80

1.79

OUTPUT VOLTAGE (V)

1.78

1.77

1.76

–50

050

–25 25 75 125

TEMPERATURE (°C)

= V

SHDN

LT1761-1.2
Output Voltage

1.220
IL = 1mA

1.215

1.210

IN

= 0V

100

1761 G03

1.205

1.200

1.195

OUTPUT VOLTAGE (V)

1.190

1.185

1.180

–25 25 75 125

–50

050

TEMPERATURE (°C)

100

1761 G05

LT1761-2
Output Voltage

2.04
IL = 1mA

2.03

2.02

2.01

2.00

1.99

OUTPUT VOLTAGE (V)

1.98

1.97

100

1761 G06

1.96

–50

050

–25 25 75 125

TEMPERATURE (°C)

100

1761 G07

LT1761-1.5
Output Voltage

1.528
IL = 1mA

1.521

1.514

1.507

1.500

1.493

OUTPUT VOLTAGE (V)

1.486

1.479

1.472

–25 25 75 125

–50

LT1761-2.5
Output Voltage

2.54
IL = 1mA

2.53

2.52

2.51

2.50

2.49

OUTPUT VOLTAGE (V)

2.48

2.47

2.46

–25 25 75 125

–50

050

TEMPERATURE (°C)

050

TEMPERATURE (°C)

100

1761 G51

100

1761 G08

1761sfe

7

LT1761 Series

TYPICAL PERFORMANCE CHARACTERISTICS

LT1761-2.8
Output Voltage

2.84
IL = 1mA

2.83

2.82

2.81

2.80

2.79

OUTPUT VOLTAGE (V)

2.78

2.77

2.76

–25 25 75 125

–50

LT1761-5
Output Voltage

5.08
IL = 1mA

5.06

5.04

5.02

5.00

4.98

OUTPUT VOLTAGE (V)

4.96

4.94

4.92

–25 25 75 125

–50

050

TEMPERATURE (°C)

050

TEMPERATURE (°C)

100

100

1761 G52

1761 G12

LT1761-3
Output Voltage

3.060
IL = 1mA

3.045

3.030

3.015

3.000

2.985

OUTPUT VOLTAGE (V)

2.970

2.955

2.940

–50

050

–25 25 75 125

TEMPERATURE (°C)

LT1761-BYP, LT1761-SD
ADJ Pin Voltage

1.240

IL = 1mA

1.235

1.230

1.225

1.220

1.215

ADJ PIN VOLTAGE (V)

1.210

1.205

1.200

–50

050

–25 25 75 125

TEMPERATURE (°C)

100

100

1761 G09

1761 G10

LT1761-3.3
Output Voltage

3.360
IL = 1mA

3.345

3.330

3.315

3.300

3.285

OUTPUT VOLTAGE (V)

3.270

3.255

3.240

–50

050

–25 25 75 125

TEMPERATURE (°C)

LT1761-1.2
Quiescent Current

250

TJ = 25°C

225

= ∞

R

L

200

175

150

125

100

75

QUIESCENT CURRENT (μA)

50

25

0

213579

0

INPUT VOLTAGE (V)

100

1761 G11

V

= V

SHDN

IN

V

= 0V

SHDN

6

8

4

10

1761 G10b

LT1761-1.5
Quiescent Current

200

TJ = 25°C

= ∞

R

L

175

150

125

100

75

50

QUIESCENT CURRENT (μA)

25

0

213579

0

8

V

SHDN

V

SHDN

6

4

INPUT VOLTAGE (V)

= V

= 0V

LT1761-1.8
Quiescent Current

200

TJ = 25°C

= ∞

R

L

175

150

125

100

75

50

QUIESCENT CURRENT (μA)

IN

8

10

1761 G53

25

0

213579

0

INPUT VOLTAGE (V)

V

= V

SHDN

IN

V

= 0V

SHDN

6

8

4

10

1761 G18

LT1761-2
Quiescent Current

200

TJ = 25°C

= ∞

R

L

175

150

125

100

75

50

QUIESCENT CURRENT (μA)

25

0

213579

0

INPUT VOLTAGE (V)

V

= V

SHDN

IN

V

= 0V

SHDN

6

8

4

10

1761 G19

1761sfe

TYPICAL PERFORMANCE CHARACTERISTICS

LT1761 Series

LT1761-2.5
Quiescent Current

200

TJ = 25°C

= ∞

R

L

175

150

125

100

75

50

QUIESCENT CURRENT (μA)

25

0

213579

0

INPUT VOLTAGE (V)

LT1761-3.3
Quiescent Current

200

TJ = 25°C

= ∞

R

L

175

150

125

100

75

50

QUIESCENT CURRENT (μA)

25

0

213579

0

INPUT VOLTAGE (V)

LT1761-2.8
Quiescent Current

200

TJ = 25°C

= ∞

R

L

175

150

125

100

75

50

QUIESCENT CURRENT (μA)

V

= V

SHDN

IN

V

= 0V

SHDN

6

8

4

10

1761 G13

25

0

213579

0

INPUT VOLTAGE (V)

V

= V

SHDN

IN

V

= 0V

SHDN

6

8

4

10

1761 G54

LT1761-5
Quiescent Current

200

TJ = 25°C

= ∞

R

L

175

150

125

100

75

50

V

= V

SHDN

IN

V

= 0V

SHDN

6

4

8

1761 G15

QUIESCENT CURRENT (μA)

25

10

0

213579

0

INPUT VOLTAGE (V)

V

= V

SHDN

IN

V

= 0V

SHDN

6

8

4

10

1761 G16

LT1761-3
Quiescent Current

200

TJ = 25°C

= ∞

R

L

175

150

125

100

75

50

QUIESCENT CURRENT (μA)

25

0

213579

0

INPUT VOLTAGE (V)

V

SHDN

V

SHDN

6

4

LT1761-BYP, LT1761-SD
Quiescent Current

30

TJ = 25°C

= 250k

R

L

= 5μA

I

25

L

V

= V

20

15

10

QUIESCENT CURRENT (μA)

5

0

02 6 10 14 18

4 8 12 16

SHDN

V

= 0V

SHDN

INPUT VOLTAGE (V)

IN

= V

= 0V

IN

8

10

1761 G14

20

1761 G17

LT1761-1.2
GND Pin Current

2.50

2.25

2.00

1.75

1.50

1.25

1.00

0.75

GND PIN CURRENT (mA)

0.50

0.25

0

RL = 12Ω

= 100mA*

I

L

RL = 1.2k
I

0123

INPUT VOLTAGE (V)

= 1mA*

L

4

TJ = 25°C

= 1.2V

*FOR V

OUT

RL = 24Ω

= 50mA*

I

L

RL = 120Ω

= 10mA*

I

L

678910

5

1761 G17b

LT1761-1.5
GND Pin Current

2.50

2.25

2.00

1.75

1.50

1.25

1.00

0.75

GND PIN CURRENT (mA)

0.50

0.25

0

RL = 15Ω

= 100mA*

I

L

0123

INPUT VOLTAGE (V)

RL = 1.5k

= 1mA*

I

L

4

TJ = 25°C
*FOR V

678910

5

OUT

RL = 30Ω

= 50mA*

I

L

RL = 150Ω

= 10mA*

I

L

= 1.5V

1761 G55

LT1761-1.8
GND Pin Current

2.50

2.25

2.00

1.75

1.50

1.25

1.00

0.75

GND PIN CURRENT (mA)

0.50

0.25

0

0123

RL = 18Ω

= 100mA*

I

L

INPUT VOLTAGE (V)

RL = 1.8k

= 1mA*

I

L

4

TJ = 25°C
*FOR V

OUT

RL = 36Ω

= 50mA*

I

L

RL = 180Ω

= 10mA*

I

L

678910

5

= 1.8V

1761 G02

1761sfe

9

LT1761 Series

TYPICAL PERFORMANCE CHARACTERISTICS

LT1761-2
GND Pin Current

2.50

2.25

2.00

1.75

1.50

1.25

1.00

0.75

GND PIN CURRENT (mA)

0.50

0.25

0

0123

RL = 20Ω

= 100mA*

I

L

INPUT VOLTAGE (V)

LT1761-3
GND Pin Current

2.50

2.25

2.00

1.75

1.50

1.25

1.00

0.75

GND PIN CURRENT (mA)

0.50

0.25

0

0123

RL = 30Ω
I

RL = 3k
I

INPUT VOLTAGE (V)

RL = 2k
I

= 1mA*

L

4

= 100mA*

L

= 1mA*

L

4

TJ = 25°C
*FOR V

OUT

RL = 40Ω

= 50mA*

I

L

RL = 200Ω

= 10mA*

I

L

678910

5

TJ = 25°C
*FOR V

OUT

RL = 60Ω

= 50mA*

I

L

RL = 300Ω

= 10mA*

I

L

678910

5

= 2V

1761 G04

= 3V

1761 G21

LT1761-2.5
GND Pin Current

2.50

2.25

2.00

1.75

1.50

1.25

1.00

0.75

GND PIN CURRENT (mA)

0.50

0.25

0

0123

RL = 25Ω
I

L

INPUT VOLTAGE (V)

LT1761-3.3
GND Pin Current

2.50

2.25

2.00

1.75

1.50

1.25

1.00

0.75

GND PIN CURRENT (mA)

0.50

0.25

0

0123

INPUT VOLTAGE (V)

= 100mA

RL = 2.5k
I

= 1mA*

L

4

RL = 33Ω

= 100mA*

I

L

RL = 3.3k

= 1mA*

I

L

4

TJ = 25°C
*FOR V

678910

5

TJ = 25°C
*FOR V

678910

5

OUT

RL = 50Ω

= 50mA*

I

L

RL = 250Ω

= 10mA*

I

L

OUT

RL = 66Ω

= 50mA*

I

L

RL = 330Ω

= 10mA*

I

L

= 2.5V

= 3.3V

1761 G20

1761 G22

LT1761-2.8
GND Pin Current

2.50

2.25

2.00

1.75

1.50

1.25

1.00

0.75

GND PIN CURRENT (mA)

0.50

0.25

0

0123

RL = 28Ω
I

L

INPUT VOLTAGE (V)

LT1761-5
GND Pin Current

2.50
TJ = 25°C

2.25

*FOR V

2.00

1.75

1.50

1.25

1.00

0.75

GND PIN CURRENT (mA)

0.50

0.25

0

0123

= 5V

OUT

INPUT VOLTAGE (V)

= 100mA

RL = 2.8k
I

= 1mA*

L

4

RL = 5k

= 1mA*

I

L

4

TJ = 25°C
*FOR V

OUT

RL = 56Ω

= 50mA*

I

L

RL = 280Ω

= 10mA*

I

L

678910

5

RL = 50Ω

= 100mA

I

L

RL = 100Ω

= 50mA*

I

L

RL = 500Ω

= 10mA*

I

L

678910

5

= 2.8V

1761 G56

1761 G23

LT1761-BYP, LT1761-SD
GND Pin Current GND Pin Current vs I

2.50

2.25

2.00

1.75

1.50

1.25

1.00

0.75

GND PIN CURRENT (mA)

0.50

0.25

0

0123

RL = 12.2Ω

= 100mA*

I

L

INPUT VOLTAGE (V)

RL = 1.22k

= 1mA*

I

L

4

TJ = 25°C

= 1.22V

*FOR V

OUT

RL = 24.4Ω

= 50mA*

I

L

RL = 122Ω

= 10mA*

I

L

678910

5

1761 G24

2.50
VIN = V

2.25

2.00

1.75

1.50

1.25

1.00

0.75

GND PIN CURRENT (mA)

0.50

0.25

0

0 102030

10

OUT(NOMINAL)

OUTPUT CURRENT (mA)

+ 1V

40

50

60 70 80 90 100

LOAD

1761 G25

SHDN Pin Threshold
(On to Off)

1.0
IL = 1mA

0.9

0.8

0.7

0.6

0.5

0.4

0.3

SHDN PIN THRESHOLD (V)

0.2

0.1

0

–50

–25

0

50

25

TEMPERATURE (°C)

100

125

1761 G26

1761sfe

75

LT1761 Series

TYPICAL PERFORMANCE CHARACTERISTICS

SHDN Pin Threshold
(Off to On) SHDN Pin Input Current SHDN Pin Input Current

1.0

0.9

0.8

0.7

0.6

0.5

0.4

0.3

SHDN PIN THRESHOLD (V)

0.2

0.1

0

–50

–25

IL = 100mA

IL = 1mA

50

25

0

TEMPERATURE (°C)

100

125

1761 G27

75

ADJ Pin Bias Current Current Limit Current Limit

100

90

80

70

60

50

40

30

ADJ PIN BIAS CURRENT (nA)

20

10

0

–50

–25

0

TEMPERATURE (oC)

50

25

75

100

125

1761 G30

1.0

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

SHDN PIN INPUT CURRENT (μA)

0.1

0

0123

350

V

= 0V

OUT

= 25°C

T

J

300

250

200

150

100

SHORT-CIRCUIT CURRENT (mA)

50

0

0

1

4

SHDN PIN VOLTAGE (V)

3

2

INPUT VOLTAGE (V)

678910

5

4

5

6

1761 G28

1761 G31

1.4

1.2

1.0

0.8

0.6

0.4

SHDN PIN INPUT CURRENT (μA)

0.2

350

300

250

200

150

CURRENT LIMIT (mA)

100

50

7

0

–50

0

–50

–25

VIN = 7V

= 0V

V

OUT

–25

50

25

0

TEMPERATURE (°C)

50

25

0

TEMPERATURE (°C)

V

= 20V

SHDN

100

100

125

1761 G29

125

1761 G32

75

75

Reverse Output Current Reverse Output Current Input Ripple Rejection

100

TJ = 25°C

= 0V

V

90

IN

CURRENT FLOWS

80

INTO OUTPUT PIN

= V

V

OUT

70

(LT1761-BYP, -SD)

60

50

LT1761-2.5

40

LT1761-2.8

30

LT1761-3

20

REVERSE OUTPUT CURRENT (μA)

10

0

0123

LT1761-BYP
LT1761-SD

LT1761-1.2

ADJ

LT1761-1.5

LT1761-1.8

LT1761-2

LT1761-5

4

5

OUTPUT VOLTAGE (V)

LT1761-3.3

678910

1761 G33

25.0

VIN = 0V
V

= 1.22V (LT1761-BYP, -SD)

OUT

22.5

V

= 1.2V (LT1761-1.2)

OUT

V

7.5

5.0

2.5

OUT

V

OUT

V

OUT

V

OUT

V

OUT

V

OUT

V

OUT

V

OUT

0

–50

= 1.5V (LT1761-1.5)
= 1.8V (LT1761-1.8)
= 2V (LT1761-2)
= 2.5V (LT1761-2.5)
= 2.8V (LT1761-2.8)
= 3V (LT1761-3)
= 3.3V (LT1761-3.3)
= 5V (LT1761-5)

LT1761-1.2,-1.5,-1.8,-2,

-2.5,-2.8,-3,-3.3,-5

25

0

–25

TEMPERATURE (°C)

LT1761-BYP,-SD

20.0

17.5

15.0

12.5

10.0

REVERSE OUTPUT CURRENT (μA)

50

75

100

125

1761 G34

80

70

LT1761-BYP

60

LT1761-5

50

40

30

RIPPLE REJECTION (dB)

20

10

0

100 100k

10 1k 10k 1M

FREQUENCY (Hz)

IL = 100mA

= V

V

IN

OUT(NOMINAL)

1V + 50mV

= 0

C

BYP

C

= 1μF

OUT

RIPPLE

RMS

C

= 10μF

OUT

11

+

1761 G35

1761sfe

LT1761 Series

TYPICAL PERFORMANCE CHARACTERISTICS

LT1761-5
Input Ripple Rejection Input Ripple Rejection

80

C

= 0.01μF

70

60

50

40

30

RIPPLE REJECTION (dB)

20

10

0

10 1k 10k 1M

BYP

C

= 100pF

BYP

IL = 100mA

= V

V

IN

OUT(NOMINAL)

1V + 50mV

= 10μF

C

OUT

100 100k

+

RIPPLE

RMS

FREQUENCY (Hz)

C

BYP

= 1000pF

1761 G36

80

70

60

50

40

30

RIPPLE REJECTION (dB)

20

VIN = V

OUT (NOMINAL)

10

0

–50

1V + 0.5V
AT f = 120Hz

= 50mA

I

L

RIPPLE

P-P

050

–25 25 75 125

TEMPERATURE (°C)

Load Regulation
ΔIL = 1mA to 50mA

0

–5

–10

–15

–20

–25

LOAD REGULATION (mV)

–30

–35

–40

–50

050

–25 25 75 125

TEMPERATURE (°C)

LT1761-BYP, -SD, -1.2
LT1761-1.5
LT1761-1.8
LT1761-2
LT1761-2.5
LT1761-2.8
LT1761-3
LT1761-3.3

LT1761-5

100

1761 G39

+

100

1761 G37

Load Regulation
ΔIL = 1mA to 100mA

0

–10

–20

–30

–40

–50

–60

–70

LOAD REGULATION (mV)

–80

–90

–100

–25 25 75 125

–50

LT1761-BYP, LT1761-SD
Minimum Input Voltage

2.5

2.0

1.5

1.0

0.5

MINIMUM INPUT VOLTAGE (V)

0

–50

–25

050

TEMPERATURE (°C)

0

TEMPERATURE (°C)

LT1761-BYP, -SD, -1.2
LT1761-1.5

LT1761-1.8
LT1761-2
LT1761-2.5
LT1761-2.8
LT1761-3
LT1761-3.3

LT1761-5

100

1761 G40

IL = 100mA

IL = 50mA

50

25

75

100

125

1761 G38

Output Noise Spectral Density Output Noise Spectral Density

10

LT1761-3.3

LT1761-2.8,-3

LT1761-5

1

LT1761-BYP,

-SD, 1.2

0.1

C

= 10μF

OUT

= 0

C

BYP

= 100mA

I

L

OUTPUT NOISE SPECTRAL DENSITY (μV/√Hz)

0.01
10 1k 10k 100k

100

LT1761-2.5

LT1761-1.5

LT1761-1.8

LT1761-2

FREQUENCY (Hz)

1761 G41

10

LT1761-5

1

LT1761-BYP

0.1
C

= 0.01μF

BYP

C

= 10μF

OUT

= 100mA

I

L

OUTPUT NOISE SPECTRAL DENSITY (μV/√Hz)

0.01
10 1k 10k 100k

100

FREQUENCY (Hz)

12

C

BYP

= 1000pF

C

= 100pF

BYP

1761 G42

RMS Output Noise vs
Bypass Capacitor

140

LT1761-5

120

)

100

RMS

80

60

40

OUTPUT NOISE (μV

20

0

10

LT1761-3.3

LT1761-3

LT1761-1.8, -2

LT1761-1.5

100 1k 10k

C

OUT

= 100mA

I

L

f = 10Hz TO 100kHz

LT1761-2.8

LT1761-2.5

LT1761-BYP, -1.2

C

(pF)

BYP

= 10μF

1761 G43

1761sfe

TYPICAL PERFORMANCE CHARACTERISTICS

LT1761 Series

RMS Output Noise vs
Load Current (10Hz to 100kHz)

160

C

= 10μF

OUT

C

= 0

0

0.01

BYP

= 0.01μF

C

BYP

0.1 1
LOAD CURRENT (mA)

140

)

120

RMS

100

80

60

OUTPUT NOISE (μV

40

20

LT1761-5
10Hz to 100kHz Output Noise
C

BYP

LT1761-5

LT1761-BYP

LT1761-5

LT1761-BYP

10 100

= 1000pF

1761 G44

V

OUT

100μV/DIV

LT1761-5
10Hz to 100kHz Output Noise
C

= 0pF

BYP

= 10μF

OUT

I

= 100mA

L

1ms/DIVC

LT1761-5
10Hz to 100kHz Output Noise
C

1761 G45

= 0.01μF

BYP

V

OUT

100μV/DIV

LT1761-5
10Hz to 100kHz Output Noise
C

= 100pF

BYP

OUT

= 100mA

I

L

= 10μF

1ms/DIVC

1761 G46

V

OUT

100μV/DIV

I

L

LT1761-5 Transient Response
C

0.2

0.1

0

–0.1

DEVIATION (V)

OUTPUT VOLTAGE

–0.2

100

50

(mA)

0

LOAD CURRENT

0 400

= 10μF

OUT

= 100mA

= 0pF

BYP

1ms/DIVC

800

1200 1600 2000

TIME (μs)

VIN = 6V

= 10μF

C

IN

= 10μF

C

OUT

1761 G46

1761 G49

V

OUT

100μV/DIV

OUT

= 100mA

I

L

LT1761-5 Transient Response
C

BYP

0.04

0.02

0

–0.02

DEVIATION (V)

OUTPUT VOLTAGE

–0.04

100

50

(mA)

0

LOAD CURRENT

0 40 60 10020

= 10μF

= 0.01μF

1ms/DIVC

80

120 140 180160 200

TIME (μs)

VIN = 6V

= 10μF

C

IN

= 10μF

C

OUT

1761 G48

1761 G50

1761sfe

13

LT1761 Series

PIN FUNCTIONS

IN (Pin 1): Input. Power is supplied to the device through
the IN pin. A bypass capacitor is required on this pin if
the device is more than six inches away from the main
input fi lter capacitor. In general, the output impedance
of a battery rises with frequency, so it is advisable to
include a bypass capacitor in battery-powered circuits. A
bypass capacitor in the range of 1μF to 10μF is suffi cient.
The LT1761 regulators are designed to withstand reverse
voltages on the IN pin with respect to ground and the OUT
pin. In the case of a reverse input, which can happen if
a battery is plugged in backwards, the device will act as
if there is a diode in series with its input. There will be
no reverse current fl ow into the regulator and no reverse
voltage will appear at the load. The device will protect both
itself and the load.

GND (Pin 2): Ground.
SHDN (Pin 3, Fixed/-SD Devices): Shutdown. The SHDN

pin is used to put the LT1761 regulators into a low power
shutdown state. The output will be off when the SHDN pin
is pulled low. The SHDN pin can be driven either by 5V logic
or open-collector logic with a pull-up resistor. The pull-up
resistor is required to supply the pull-up current of the
open-collector gate, normally several microamperes, and
the SHDN pin current, typically 1μA. If unused, the SHDN
pin must be connected to V
if the SHDN pin is not connected. For the LT1761-BYP, the
SHDN pin is internally connected to V

. The device will not function

IN

.

IN

BYP (Pins 3/4, Fixed/-BYP Devices): Bypass. The BYP
pin is used to bypass the reference of the LT1761 regula­tors to achieve low noise performance from the regulator.
The BYP pin is clamped internally to ±0.6V (one V
ground. A small capacitor from the output to this pin will
bypass the reference to lower the output voltage noise.
A maximum value of 0.01μF can be used for reducing
output voltage noise to a typical 20μV
to 100kHz bandwidth. If not used, this pin must be left
unconnected.

ADJ (Pin 4, Adjustable Devices Only): Adjust Pin. For the
adjustable LT1761, this is the input to the error amplifi er.
This pin is internally clamped to ±7V. It has a bias current
of 30nA which fl ows into the pin (see curve of ADJ Pin
Bias Current vs Temperature in the Typical Performance
Characteristics section). The ADJ pin voltage is 1.22V
referenced to ground and the output voltage range is

1.22V to 20V.
OUT (Pin 5): Output. The output supplies power to the load.

A minimum output capacitor of 1μF is required to prevent
oscillations. Larger output capacitors will be required for
applications with large transient loads to limit peak volt­age transients. See the Applications Information section
for more information on output capacitance and reverse
output characteristics.

over a 10Hz

RMS

) from

BE

14

1761sfe

APPLICATIONS INFORMATION

LT1761 Series

The LT1761 series are 100mA low dropout regulators with
micropower quiescent current and shutdown. The devices
are capable of supplying 100mA at a dropout voltage of
300mV. Output voltage noise can be lowered to 20μV

RMS

over a 10Hz to 100kHz bandwidth with the addition of a

0.01μF reference bypass capacitor. Additionally, the refer­ence bypass capacitor will improve transient response of
the regulator, lowering the settling time for transient load
conditions. The low operating quiescent current (20μA)
drops to less than 1μA in shutdown. In addition to the
low quiescent current, the LT1761 regulators incorporate
several protection features which make them ideal for use
in battery-powered systems. The devices are protected
against both reverse input and reverse output voltages.
In battery backup applications where the output can be
held up by a backup battery when the input is pulled to
ground, the LT1761-X acts like it has a diode in series with
its output and prevents reverse current fl ow. Additionally,
in dual supply applications where the regulator load is
returned to a negative supply, the output can be pulled
below ground by as much as 20V and still allow the device
to start and operate.

Adjustable Operation

The adjustable version of the LT1761 has an output voltage
range of 1.22V to 20V. The output voltage is set by the
ratio of two external resistors as shown in Figure 1. The
device servos the output to maintain the ADJ pin voltage
at 1.22V referenced to ground. The current in R1 is then
equal to 1.22V/R1 and the current in R2 is the current in
R1 plus the ADJ pin bias current. The ADJ pin bias cur­rent, 30nA at 25°C, fl ows through R2 into the ADJ pin.
The output voltage can be calculated using the formula in
Figure 1. The value of R1 should be no greater than 250k
to minimize errors in the output voltage caused by the

ADJ pin bias current. Note that in shutdown the output is
turned off and the divider current will be zero. Curves of
ADJ Pin Voltage vs Temperature and ADJ Pin Bias Cur­rent vs Temperature appear in the Typical Performance
Characteristics.

The adjustable device is tested and specifi ed with the ADJ
pin tied to the OUT pin for an output voltage of 1.22V.
Specifi cations for output voltages greater than 1.22V will
be proportional to the ratio of the desired output voltage
to 1.22V: V

/1.22V. For example, load regulation for an

OUT

output current change of 1mA to 100mA is –1mV typical
at V

= 1.22V. At V

OUT

= 12V, load regulation is:

OUT

(12V/1.22V)(–1mV) = –9.8mV

Bypass Capacitance and Low Noise Performance

The LT1761 regulators may be used with the addition of
a bypass capacitor from V

to the BYP pin to lower

OUT

output voltage noise. A good quality low leakage capacitor
is recommended. This capacitor will bypass the reference
of the regulator, providing a low frequency noise pole. The
noise pole provided by this bypass capacitor will lower the
output voltage noise to as low as 20μV

with the addition

RMS

of a 0.01μF bypass capacitor. Using a bypass capacitor has
the added benefi t of improving transient response. With no
bypass capacitor and a 10μF output capacitor, a 10mA to
100mA load step will settle to within 1% of its fi nal value
in less than 100μs. With the addition of a 0.01μF bypass
capacitor, the output will stay within 1% for a 10mA to
100mA load step (see LT1761-5 Transient Response in
Typical Performance Characteristics section). However,
regulator start-up time is proportional to the size of the
bypass capacitor, slowing to 15ms with a 0.01μF bypass
capacitor and 10μF output capacitor.

IN

V

IN

OUT

LT1761

GND

R2

ADJ

R1

Figure 1. Adjustable Operation

1761 F01

V

OUT

+

¥

´

2





¦

§

AT 25 C

R



IR



µ

1

R

¶

122 1

VV



OUT ADJ



122

VV

ADJ

o

30

InA

ADJ

OUTPUT RANGE = 1.22V TO 20V

2

1761sfe

15

LT1761 Series

APPLICATIONS INFORMATION

Output Capacitance and Transient Response

The LT1761 regulators are designed to be stable with a
wide range of output capacitors. The ESR of the output
capacitor affects stability, most notably with small capaci­tors. A minimum output capacitor of 1μF with an ESR of
3Ω or less is recommended to prevent oscillations. The
LT1761-X is a micropower device and output transient
response will be a function of output capacitance. Larger
values of output capacitance decrease the peak deviations
and provide improved transient response for larger load
current changes. Bypass capacitors, used to decouple
individual components powered by the LT1761-X, will
increase the effective output capacitor value. With larger
capacitors used to bypass the reference (for low noise
operation), larger values of output capacitors are needed.
For 100pF of bypass capacitance, 2.2μF of output capaci­tor is recommended. With a 330pF bypass capacitor or
larger, a 3.3μF output capacitor is recommended. The
shaded region of Figure 2 defi nes the region over which
the LT1761 regulators are stable. The minimum ESR
needed is defi ned by the amount of bypass capacitance
used, while the maximum ESR is 3Ω.

and temperature coeffi cients as shown in Figures 3 and 4.
When used with a 5V regulator, a 16V 10μF Y5V capacitor
can exhibit an effective value as low as 1μF to 2μF for the
DC bias voltage applied and over the operating tempera­ture range. The X5R and X7R dielectrics result in more
stable characteristics and are more suitable for use as the
output capacitor. The X7R type has better stability across
temperature, while the X5R is less expensive and is avail­able in higher values. Care still must be exercised when
using X5R and X7R capacitors; the X5R and X7R codes
only specify operating temperature range and maximum
capacitance change over temperature. Capacitance change
due to DC bias with X5R and X7R capacitors is better than
Y5V and Z5U capacitors, but can still be signifi cant enough
to drop capacitor values below appropriate levels. Capaci­tor DC bias characteristics tend to improve as component
case size increases, but expected capacitance at operating
voltage should be verifi ed.

20

0

–20

BOTH CAPACITORS ARE 16V,
1210 CASE SIZE, 10μF

X5R

Extra consideration must be given to the use of ceramic
capacitors. Ceramic capacitors are manufactured with a
variety of dielectrics, each with different behavior across
temperature and applied voltage. The most common
dielectrics used are specifi ed with EIA temperature char­acteristic codes of Z5U, Y5V, X5R and X7R. The Z5U and
Y5V dielectrics are good for providing high capacitances
in a small package, but they tend to have strong voltage

4.0

3.5

3.0

2.5

2.0

ESR (Ω)

1.5

1.0

0.5

0

C

BYP

C

1

STABLE REGION

= 0

= 100pF

BYP

C

= 330pF

BYP

C

> 3300pF

BYP

310

245

OUTPUT CAPACITANCE (μF)

Figure 2. Stability

6

9

78

1761 F02

–40

–60

CHANGE IN VALUE (%)

–80

–100

0

26

4

DC BIAS VOLTAGE (V)

Y5V

14

8

12

10

16

1761 F03

Figure 3. Ceramic Capacitor DC Bias Characteristics

40

20

0

–20

–40

–60

CHANGE IN VALUE (%)

–80

BOTH CAPACITORS ARE 16V,
1210 CASE SIZE, 10μF

–100

–50

–25 0

25 75

TEMPERATURE (°C)

X5R

Y5V

50 100 125

1761 F04

Figure 4. Ceramic Capacitor Temperature Characteristics

1761sfe

16

APPLICATIONS INFORMATION

LT1761 Series

Voltage and temperature coeffi cients are not the only
sources of problems. Some ceramic capacitors have a
piezoelectric response. A piezoelectric device generates
voltage across its terminals due to mechanical stress,
similar to the way a piezoelectric accelerometer or micro­phone works. For a ceramic capacitor the stress can be
induced by vibrations in the system or thermal transients.
The resulting voltages produced can cause appreciable
amounts of noise, especially when a ceramic capacitor is
used for noise bypassing. A ceramic capacitor produced
Figure 5’s trace in response to light tapping from a pencil.
Similar vibration induced behavior can masquerade as
increased output voltage noise.

V

OUT

500μV/DIV

LT1761-5

= 10μF

C

OUT

= 0.01μF

C

BYP

= 100mA

I

LOAD

Figure 5. Noise Resulting from Tapping on a Ceramic Capacitor

100ms/DIV

1761 F05

Thermal Considerations

The power handling capability of the device will be limited
by the maximum rated junction temperature (125°C). The
power dissipated by the device will be made up of two
components:

1. Output current multiplied by the input/output voltage
differential: (I

OUT

)(VIN – V

OUT

), and

2. GND pin current multiplied by the input voltage:

)(VIN).

(I

GND

The ground pin current can be found by examining the
GND Pin Current curves in the Typical Performance Char­acteristics section. Power dissipation will be equal to the
sum of the two components listed above.

The LT1761 series regulators have internal thermal limiting
designed to protect the device during overload conditions.

For continuous normal conditions, the maximum junction
temperature rating of 125°C must not be exceeded. It is
important to give careful consideration to all sources of
thermal resistance from junction to ambient. Additional
heat sources mounted nearby must also be considered.

For surface mount devices, heat sinking is accomplished
by using the heat spreading capabilities of the PC board
and its copper traces. Copper board stiffeners and plated
through-holes can also be used to spread the heat gener­ated by power devices.

The following table lists thermal resistance for several
different board sizes and copper areas. All measurements
were taken in still air on 3/32" FR-4 board with one ounce
copper.

Table 1. Measured Thermal Resistance

COPPER AREA

2

2500mm
1000mm

225mm
100mm

50mm

*Device is mounted on topside.

2500mm22500mm

2

2500mm22500mm

2

2500mm22500mm

2

2500mm22500mm

2

2500mm22500mm

BOARD AREA

THERMAL RESISTANCE

(JUNCTION-TO-AMBIENT)TOPSIDE* BACKSIDE

2

2

2

2

2

125°C/W
125°C/W
130°C/W
135°C/W
150°C/W

Calculating Junction Temperature

Example: Given an output voltage of 3.3V, an input voltage
range of 4V to 6V, an output current range of 0mA to 50mA
and a maximum ambient temperature of 50°C, what will
the maximum junction temperature be?

The power dissipated by the device will be equal to:
I

OUT(MAX)(VIN(MAX)

– V

OUT

) + I

GND(VIN(MAX)

)
where,
I

OUT(MAX)

V

IN(MAX)

I

GND

= 50mA

= 6V

at (I

= 50mA, VIN = 6V) = 1mA

OUT

So,
P = 50mA(6V – 3.3V) + 1mA(6V) = 0.14W
The thermal resistance will be in the range of 125°C/W to

150°C/W depending on the copper area. So the junction

1761sfe

17

LT1761 Series

APPLICATIONS INFORMATION

temperature rise above ambient will be approximately
equal to:

0.14W(150°C/W) = 21.2°C
The maximum junction temperature will then be equal to

the maximum junction temperature rise above ambient
plus the maximum ambient temperature or:

T

= 50°C + 21.2°C = 71.2°C

JMAX

Protection Features

The LT1761 regulators incorporate several protection
features which make them ideal for use in battery-pow­ered circuits. In addition to the normal protection features
associated with monolithic regulators, such as current
limiting and thermal limiting, the devices are protected
against reverse input voltages, reverse output voltages
and reverse voltages from output to input.

Current limit protection and thermal overload protection
are intended to protect the device against current overload
conditions at the output of the device. For normal operation,
the junction temperature should not exceed 125°C.

The input of the device will withstand reverse voltages
of 20V. Current fl ow into the device will be limited to less
than 1mA (typically less than 100μA) and no negative
voltage will appear at the output. The device will protect
both itself and the load. This provides protection against
batteries which can be plugged in backward.

The output of the LT1761-X can be pulled below ground
without damaging the device. If the input is left open circuit
or grounded, the output can be pulled below ground by
20V. For fi xed voltage versions, the output will act like a
large resistor, typically 500k or higher, limiting current fl ow
to typically less than 100μA. For adjustable versions, the
output will act like an open circuit; no current will fl ow out
of the pin. If the input is powered by a voltage source, the
output will source the short-circuit current of the device
and will protect itself by thermal limiting. In this case,
grounding the SHDN pin will turn off the device and stop
the output from sourcing the short-circuit current.

The ADJ pin of the adjustable device can be pulled above
or below ground by as much as 7V without damaging the
device. If the input is left open circuit or grounded, the

ADJ pin will act like an open circuit when pulled below
ground and like a large resistor (typically 100k) in series
with a diode when pulled above ground.

In situations where the ADJ pin is connected to a resistor
divider that would pull the ADJ pin above its 7V clamp volt­age if the output is pulled high, the ADJ pin input current
must be limited to less than 5mA. For example, a resistor
divider is used to provide a regulated 1.5V output from the

1.22V reference when the output is forced to 20V. The top
resistor of the resistor divider must be chosen to limit the
current into the ADJ pin to less than 5mA when the ADJ
pin is at 7V. The 13V difference between output and ADJ
pin divided by the 5mA maximum current into the ADJ pin
yields a minimum top resistor value of 2.6k.

In circuits where a backup battery is required, several
different input/output conditions can occur. The output
voltage may be held up while the input is either pulled
to ground, pulled to some intermediate voltage or is left
open circuit. Current fl ow back into the output will follow
the curve shown in Figure 6.

When the IN pin of the LT1761-X is forced below the OUT
pin or the OUT pin is pulled above the IN pin, input cur­rent will typically drop to less than 2μA. This can happen
if the input of the device is connected to a discharged
(low voltage) battery and the output is held up by either
a backup battery or a second regulator circuit. The state
of the SHDN pin will have no effect on the reverse output
current when the output is pulled above the input.

100

TJ = 25°C

= 0V

V

90

IN

CURRENT FLOWS

80

INTO OUTPUT PIN

= V

V

OUT

70

(LT1761-BYP, -SD)

60

50

LT1761-2.5

40

LT1761-2.8

30

LT1761-3

20

REVERSE OUTPUT CURRENT (μA)

10

0

0123

Figure 6. Reverse Output Current

LT1761-BYP
LT1761-SD

LT1761-1.2

ADJ

LT1761-1.5

LT1761-1.8

LT1761-2

LT1761-5

4

5

OUTPUT VOLTAGE (V)

LT1761-3.3

678910

1761 F06

1761sfe

18

PACKAGE DESCRIPTION

LT1761 Series

S5 Package

5-Lead Plastic TSOT-23

(Reference LTC DWG # 05-08-1635)

0.62

MAX

3.85 MAX

0.20 BSC

DATUM ‘A’

NOTE:

1. DIMENSIONS ARE IN MILLIMETERS

2. DRAWING NOT TO SCALE

3. DIMENSIONS ARE INCLUSIVE OF PLATING

4. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR

5. MOLD FLASH SHALL NOT EXCEED 0.254mm

6. JEDEC PACKAGE REFERENCE IS MO-193

2.62 REF

RECOMMENDED SOLDER PAD LAYOUT

PER IPC CALCULATOR

0.30 – 0.50 REF

0.95
REF

1.22 REF

1.4 MIN

0.09 – 0.20
(NOTE 3)

2.80 BSC

1.50 – 1.75
(NOTE 4)

1.00 MAX

PIN ONE

0.95 BSC

0.80 – 0.90

2.90 BSC
(NOTE 4)

1.90 BSC

0.30 – 0.45 TYP
5 PLCS (NOTE 3)

0.01 – 0.10

S5 TSOT-23 0302 REV B

Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa­tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.

1761sfe

19

LT1761 Series

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Q

Q

Includes 2.5V Reference and Comparator

, SOT-223 Package

Q

, 0.26V Dropout Voltage, SOT-223 Package

Q

, Reverse-Battery Protection

Q

500mV Dropout Voltage

RMS

, SOT-223 Package

RMS

, 340mV Dropout Voltage

RMS

®

Operation, Monolithic, 100% Duty Cycle

Noise

RMS

Noise

RMS

(100kHz BW)

Noise

RMS

20

Linear Technology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

[phone] ● FAX: [phone]

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www.linear.com

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LT 0909 REV E • PRINTED IN USA

© LINEAR TECHNOLOGY CORPORATION 2005