LT1761MPS5-5#TRM_技术文档

LT1761 Series

100mA, Low Noise,

LDO Micropower

Regulators in TSOT-23

FEATURES

DESCRIPTION

The LT^®1761 series are micropower, low noise, low

dropout regulators. With an external 0.01μF bypass

n

Low Noise: 20μV

(10Hz to 100kHz)

RMS

n

Low Quiescent Current: 20μA

Wide Input Voltage Range: 1.8V to 20V

Output Current: 100mA

Very Low Shutdown Current: <0.1μA

Low Dropout Voltage: 300mV at 100mA

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

2.8V, 3V, 3.3V, 5V

n

capacitor, output noise drops to 20μV

over a 10Hz to

RMS

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

outputcurrentwithadropoutvoltageof300mV.Quiescent

current is well controlled, not rising in dropout as it does

with many other regulators.

n

Adjustable Output from 1.22V to 20V

Stable with 1μF Output Capacitor

Stable with Aluminum, Tantalum or

Ceramic Capacitors

TheLT1761regulatorsarestablewithoutputcapacitorsas

low as 1μF. Small ceramic capacitors can be used without

the series resistance required by other regulators.

n

Reverse-Battery Protected

No Reverse Current

No Protection Diodes Needed

Internal protection circuitry includes reverse battery

protection, current limiting, thermal limiting and reverse

current protection. The device is available in ﬁxed 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.

Overcurrent and Overtemperature Protected

Available in Tiny 5-Lead TSOT-23 Package

APPLICATIONS

n

Cellular Phones

n

Pagers

n

Battery-Powered Systems

L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks

of Linear Technology Corporation. All other trademarks are the property of their respective

owners.

n

Frequency Synthesizers

n

Wireless Modems

TYPICAL APPLICATION

10Hz to 100kHz Output Noise

5V Low Noise Regulator

5V AT100mA

20μV NOISE

10μF

IN

OUT

BYP

V

RMS

IN

+

V

OUT

5.4V TO

20V

1μF

0.01μF

LT1761-5

20μV

RMS

100μV/DIV

SHDN

GND

1761 TA01

1761 TA01b

1761sff

1

LT1761 Series

(Note 1)

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

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

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

TOP VIEW

IN 1

GND 2

BYP 3

5 OUT

4 ADJ

IN 1

GND 2

5 OUT

4 ADJ

IN 1

GND 2

5 OUT

4 BYP

SHDN 3

S5 PACKAGE

5-LEAD PLASTIC TSOT-23

S5 PACKAGE

5-LEAD PLASTIC TSOT-23

S5 PACKAGE

5-LEAD PLASTIC TSOT-23

T

= 150°C, θ = 250°C/W

T

JMAX

= 150°C, θ = 250°C/W

T

= 150°C, θ = 250°C/W

JMAX JA

JMAX

JA

SEE APPLICATIONS INFORMATION SECTION

ORDER INFORMATION

LEAD FREE FINISH

LT1761ES5-BYP#PBF

LT1761IS5-BYP#PBF

LT1761ES5-SD#PBF

LT1761IS5-SD#PBF

LT1761ES5-1.2#PBF

LT1761IS5-1.2#PBF

LT1761ES5-1.5#PBF

LT1761IS5-1.5#PBF

LT1761ES5-1.8#PBF

LT1761IS5-1.8#PBF

LT1761MPS5-1.8#PBF

LT1761ES5-2#PBF

LT1761IS5-2#PBF

TAPE AND REEL

PART MARKING *

LTGC

LTGH

LTCDS

LTMT

LTJM

LTDCH

LTJE

LTGD

LTLB

LTGE

LTGF

PACKAGE DESCRIPTION

5-Lead Plastic TSOT-23

TEMPERATURE RANGE

LT1761ES5-BYP#TRPBF

LT1761IS5-BYP#TRPBF

LT1761ES5-SD#TRPBF

LT1761IS5-SD#TRPBF

LT1761ES5-1.2#TRPBF

LT1761IS5-1.2#TRPBF

LT1761ES5-1.5#TRPBF

LT1761IS5-1.5#TRPBF

LT1761ES5-1.8#TRPBF

LT1761IS5-1.8#TRPBF

LT1761MPS5-1.8#TRPBF

LT1761ES5-2#TRPBF

LT1761IS5-2#TRPBF

LT1761ES5-2.5#TRPBF

LT1761IS5-2.5#TRPBF

LT1761ES5-2.8#TRPBF

LT1761IS5-2.8#TRPBF

LT1761ES5-3#TRPBF

LT1761IS5-3#TRPBF

LT1761ES5-3.3#TRPBF

LT1761IS5-3.3#TRPBF

LT1761MPS5-3.3#TRPBF

–40°C to 125°C

–55°C to 125°C

–40°C to 125°C

–55°C to 125°C

5-Lead Plastic TSOT-23

LT1761ES5-2.5#PBF

LT1761IS5-2.5#PBF

LT1761ES5-2.8#PBF

LT1761IS5-2.8#PBF

LT1761ES5-3#PBF

LT1761IS5-3#PBF

LT1761ES5-3.3#PBF

LT1761IS5-3.3#PBF

LT1761MPS5-3.3#PBF

LTGF

1761sff

2

LT1761 Series

ORDER INFORMATION

LEAD FREE FINISH

LT1761ES5-5#PBF

LT1761IS5-5#PBF

LT1761MPS5-5#PBF

LEAD BASED FINISH

LT1761ES5-BYP

LT1761IS5-BYP

LT1761ES5-SD

LT1761IS5-SD

LT1761ES5-1.2

LT1761IS5-1.2

LT1761ES5-1.5

LT1761IS5-1.5

LT1761ES5-1.8

LT1761IS5-1.8

LT1761MPS5-1.8

LT1761ES5-2

TAPE AND REEL

PART MARKING *

LTGG

PART MARKING *

LTGC

LTGH

LTCDS

LTMT

LTJM

LTDCH

LTJE

LTGD

LTLB

LTGE

LTGF

PACKAGE DESCRIPTION

5-Lead Plastic TSOT-23

PACKAGE DESCRIPTION

5-Lead Plastic TSOT-23

TEMPERATURE RANGE

–40°C to 125°C

–55°C to 125°C

TEMPERATURE RANGE

–40°C to 125°C

–55°C to 125°C

–40°C to 125°C

–55°C to 125°C

–40°C to 125°C

–55°C to 125°C

LT1761ES5-5#TRPBF

LT1761IS5-5#TRPBF

LT1761MPS5-5#TRPBF

TAPE AND REEL

LT1761ES5-BYP#TR

LT1761IS5-BYP#TR

LT1761ES5-SD#TR

LT1761IS5-SD#TR

LT1761ES5-1.2#TR

LT1761IS5-1.2#TR

LT1761ES5-1.5#TR

LT1761IS5-1.5#TR

LT1761ES5-1.8#TR

LT1761IS5-1.8#TR

LT1761MPS5-1.8#TR

LT1761ES5-2#TR

LT1761IS5-2#TR

LT1761ES5-2.5#TR

LT1761IS5-2.5#TR

LT1761ES5-2.8#TR

LT1761IS5-2.8#TR

LT1761ES5-3#TR

LT1761IS5-3#TR

LT1761IS5-2

LT1761ES5-2.5

LT1761IS5-2.5

LT1761ES5-2.8

LT1761IS5-2.8

LT1761ES5-3

LT1761IS5-3

LT1761ES5-3.3

LT1761IS5-3.3

LT1761MPS5-3.3

LT1761ES5-5

LT1761IS5-5

LT1761MPS5-5

LT1761ES5-3.3#TR

LT1761IS5-3.3#TR

LT1761MPS5-3.3#TR

LT1761ES5-5#TR

LT1761IS5-5#TR

LTGG

LT1761MPS5-5#TR

Consult LTC Marketing for parts speciﬁed with wider operating temperature ranges. *The temperature grade is identiﬁed by a label on the shipping container.

For more information on lead free part marking, go to: http://www.linear.com/leadfree/

For more information on tape and reel speciﬁcations, go to: http://www.linear.com/tapeandreel/

1761sff

3

LT1761 Series

ELECTRICAL CHARACTERISTICS ^Thel denotes the speciﬁcations which apply over the full operating

temperature range, otherwise speciﬁcations are at T_A= 25°C. (Note 2)

PARAMETER

CONDITIONS

= 100mA

MIN

TYP

MAX

UNITS

l

Minimum Input Voltage (Notes 3, 11)

Regulated Output Voltage (Note 4)

I

1.8

2.3

V

LOAD

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

V

= 2V, I

= 1mA

LOAD

1.185

1.170

1.150

1.2

1.215

1.230

1.240

V

IN

l

2.3V < V < 20V, 1mA < I

< 50mA

IN

LOAD

2.3V < V < 20V, 1mA < I

< 100mA

V

IN

= 2V, I

= 1mA

LOAD

1.478

1.457

1.436

1.5

1.522

1.538

1.555

V

l

2.5V < V < 20V, 1mA < I

< 50mA

< 100mA

IN

LOAD

2.5V < V < 20V, 1mA < I

V

IN

= 2.3V, I

= 1mA

LOAD

1.775

1.750

1.725

1.8

1.825

1.845

1.860

V

l

2.8V < V < 20V, 1mA < I

< 50mA

< 100mA

IN

LOAD

2.8V < V < 20V, 1mA < I

V

= 2.5V, I

IN

= 1mA

LOAD

1.970

1.945

1.920

2

2.030

2.045

2.060

V

IN

l

3V < V < 20V, 1mA < I

< 50mA

< 100mA

LOAD

3V < V < 20V, 1mA < I

V

IN

= 3V, I

= 1mA

LOAD

2.465

2.435

2.415

2.5

2.535

2.565

2.575

V

l

3.5V < V < 20V, 1mA < I

< 50mA

< 100mA

IN

LOAD

3.5V < V < 20V, 1mA < I

V

IN

= 3.3V, I

= 1mA

LOAD

2.762

2.732

2.706

2.8

2.838

2.868

2.884

V

l

3.8V < V < 20V, 1mA < I

< 50mA

< 100mA

IN

LOAD

3.8V < V < 20V, 1mA < I

V

= 3.5V, I

IN

= 1mA

LOAD

2.960

2.930

2.900

3

3.040

3.070

3.090

V

IN

l

4V < V < 20V, 1mA < I

< 50mA

< 100mA

LOAD

4V < V < 20V, 1mA < I

V

IN

= 3.8V, I

= 1mA

LOAD

3.250

3.230

3.190

3.3

3.350

3.370

3.400

V

l

4.3V < V < 20V, 1mA < I

< 50mA

< 100mA

IN

LOAD

4.3V < V < 20V, 1mA < I

V

= 5.5V, I

IN

= 1mA

LOAD

4.935

4.900

4.850

5

5.065

5.100

5.120

V

IN

l

6V < V < 20V, 1mA < I

< 50mA

< 100mA

LOAD

6V < V < 20V, 1mA < I

ADJ Pin Voltage (Note 3, 4)

Line Regulation

V

IN

= 2V, I

= 1mA

LOAD

1.205

1.190

1.170

1.220

1.235

1.250

1.260

V

l

2.3V < V < 20V, 1mA < I

< 50mA

< 100mA

IN

LOAD

2.3V < V < 20V, 1mA < I

l

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)

1

10

mV

ΔV = 2V to 20V, I

= 1mA

IN

LOAD

ΔV = 2V to 20V, I

ΔV = 2.3V to 20V, I

= 1mA

ΔV = 2.5V to 20V, I

ΔV = 3V to 20V, I

= 1mA

LOAD

ΔV = 3.3V to 20V, I

= 1mA

LOAD

ΔV = 3.5V to 20V, I

ΔV = 3.8V to 20V, I

ΔV = 5.5V to 20V, I

IN

ΔV = 2V to 20V, I

= 1mA

LOAD

1761sff

4

LT1761 Series

ELECTRICAL CHARACTERISTICS ^Thel denotes the speciﬁcations which apply over the full operating

temperature range, otherwise speciﬁcations are at T_A= 25°C. (Note 2)

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

Load Regulation

LT1761-1.2

1

6

mV

V

IN

V

IN

V

IN

V

IN

= 2.3V, ΔI

= 1mA to 50mA

= 1mA to 100mA

LOAD

l

12

50

1

LT1761-1.5

LT1761-1.8

LT1761-2

10

14

20

35

30

55

mV

V

= 2.5V, ΔI

= 1mA to 50mA

= 1mA to 100mA

IN

LOAD

l

10

15

20

35

30

60

mV

V

IN

V

IN

V

IN

V

IN

= 2.8V, ΔI

= 1mA to 50mA

= 1mA to 100mA

LOAD

l

10

15

20

35

65

mV

V

IN

V

IN

V

IN

V

IN

= 3V, ΔI

= 1mA to 50mA

= 1mA to 100mA

LOAD

l

LT1761-2.5

LT1761-2.8

LT1761-3

10

20

35

40

80

mV

V

= 3.5V, ΔI

= 1mA to 50mA

= 1mA to 100mA

IN

LOAD

l

10

20

38

40

86

mV

V

IN

V

IN

V

IN

V

IN

= 3.8V, ΔI

= 1mA to 50mA

= 1mA to 100mA

LOAD

l

10

20

40

90

mV

V

IN

V

IN

V

IN

V

IN

= 4V, ΔI

= 1mA to 50mA

= 1mA to 100mA

LOAD

l

LT1761-3.3

LT1761-5

10

20

40

mV

V

= 4.3V, ΔI

= 1mA to 50mA

= 1mA to 100mA

IN

LOAD

l

40

100

15

25

30

60

mV

V

= 6V, ΔI

= 1mA to 50mA

= 1mA to 100mA

IN

LOAD

l

65

150

LT1761 (Note 3)

1

6

mV

V

IN

V

IN

V

IN

V

IN

= 2.3V, ΔI

= 1mA to 50mA

= 1mA to 100mA

LOAD

l

12

50

Dropout Voltage

I

= 1mA

0.10

0.17

0.24

0.30

0.15

0.19

V

LOAD

l

V

= V

OUT(NOMINAL)

IN

(Notes 5, 6, 11)

I

= 10mA

0.22

0.29

V

LOAD

I

= 50mA

0.28

0.38

V

LOAD

I

= 100mA

0.35

0.45

V

LOAD

1761sff

5

LT1761 Series

ELECTRICAL CHARACTERISTICS ^Thel denotes the speciﬁcations which apply over the full operating

temperature range, otherwise speciﬁcations are at T_A= 25°C. (Note 2)

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

l

GND Pin Current

I

= 0mA

20

55

45

100

400

2

μA

LOAD

V

= V

= 1mA

IN

OUT(NOMINAL)

(Notes 5, 7)

= 10mA

= 50mA

= 100mA

230

1

μA

mA

2.2

4

Output Voltage Noise

ADJ Pin Bias Current

Shutdown Threshold

C

= 10μF, C

= 0.01μF, I

= 100mA, BW = 10Hz to 100kHz

20

30

μV

RMS

OUT

BYP

LOAD

(Notes 3, 8)

100

2

nA

l

V

= Off to On

= On to Off

0.8

0.65

V

OUT

0.25

l

SHDN Pin Current

(Note 9)

V

SHDN

V

SHDN

= 0V

= 20V

0

1

0.5

3

μA

Quiescent Current in Shutdown

Ripple Rejection (Note 3)

V

= 6V, V

= 0V

0.01

65

0.1

μA

dB

IN

SHDN

– V

= 1.5V (Avg), V

= 0.5V , f

P-P RIPPLE

= 120Hz,

= –5%

55

IN

OUT

RIPPLE

I

= 50mA

LOAD

Current Limit

V

IN

V

IN

= 7V, V

= 0V

200

mA

OUT

OUT(NOMINAL)

l

= V

+ 1V or 2.3V (Note 12), ΔV

110

OUT

Input Reverse Leakage Current

V

IN

= –20V, V

= 0V

OUT

1

mA

Reverse Output Current

(Note 10)

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)

V

= 1.2V, V < 1.2V

10

5

20

10

μA

OUT

IN

V

= 1.5V, V < 1.5V

IN

= 1.8V, V < 1.8V

IN

= 2V, V < 2V

IN

= 2.5V, V < 2.5V

IN

= 2.8V, V < 2.8V

IN

= 3V, V < 3V

IN

= 3.3V, V < 3.3V

IN

= 5V, V < 5V

IN

= 1.22V, V < 1.22V

IN

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 6: Dropout voltage is the minimum input to output voltage differential

needed to maintain regulation at a speciﬁed output current. In dropout, the

output voltage will be equal to: V – V

.

IN

DROPOUT

Note 7: GND pin current is tested with V = V

or V = 2.3V

IN

OUT(NOMINAL)

Note 2: The LT1761 regulators are tested and speciﬁed under pulse load

(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 speciﬁcation. 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 ﬂows into the ADJ pin.

Note 9: SHDN pin current ﬂows 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 ﬂows into the OUT

pin and out the GND pin.

conditions such that T ≈ T . The LT1761E is 100% production tested

J

A

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

A

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 speciﬁed 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 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: To satisfy requirements for minimum input voltage, the LT1761

(adjustable version) is tested and speciﬁed 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 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

speciﬁcation 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

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

IN

OUT(NOMINAL)

IN

1761sff

6

LT1761 Series

TYPICAL PERFORMANCE CHARACTERISTICS

Typical Dropout Voltage

Guaranteed Dropout Voltage

Dropout Voltage

500

450

400

350

300

250

200

150

100

50

500

450

400

350

300

250

200

150

100

50

500

450

400

350

300

250

200

150

100

50

= TEST POINTS

T

≤ 125°C

J

T

= 125°C

J

I

L

= 100mA

T

≤ 25°C

J

I

= 50mA

= 10mA

L

T

= 25°C

J

I

L

I

= 1mA

L

0

40

50

TEMPERATURE (°C)

125

40

50 60 70 80 90 100

OUTPUT CURRENT (mA)

0

10 20 30

50 60 70 80 90 100

–50 –25

0

25

75 100

0

10 20 30

OUTPUT CURRENT (mA)

1761 G01

1761 G01.1

1761 G00

LT1761-1.2

Output Voltage

LT1761-1.5

Quiescent Current

Output Voltage

1.220

1.215

1.210

1.205

1.200

1.195

1.190

1.185

1.180

1.528

1.521

1.514

1.507

1.500

1.493

1.486

1.479

1.472

40

35

30

25

20

15

10

5

V

= 6V

I

= 1mA

I

= 1mA

IN

L

R

= ∞ (250k FOR LT1761-BYP, -SD)

I

= 0 (5μA FOR LT1761-BYP, -SD)

L

V

= V

IN

SHDN

V

= 0V

50

SHDN

0

–25

0

25

50

75

125

–25

0

25

50

75

125

–50

100

–50

100

–25

0

25

75

125

–50

100

TEMPERATURE (°C)

1761 G05

1761 G51

1761 G03

LT1761-1.8

Output Voltage

LT1761-2

Output Voltage

LT1761-2.5

Output Voltage

1.84

1.83

1.82

1.81

1.80

1.79

1.78

1.77

1.76

2.04

2.03

2.02

2.01

2.00

1.99

1.98

1.97

1.96

2.54

2.53

2.52

2.51

2.50

2.49

2.48

2.47

2.46

I

= 1mA

I

= 1mA

I

= 1mA

L

–25

0

25

50

75

125

–25

0

25

50

75

125

–25

0

25

50

75

125

–50

100

–50

100

–50

100

TEMPERATURE (°C)

1761 G06

1761 G07

1761 G08

1761sff

7

LT1761 Series

TYPICAL PERFORMANCE CHARACTERISTICS

LT1761-2.8

Output Voltage

LT1761-3

Output Voltage

LT1761-3.3

Output Voltage

2.84

2.83

2.82

2.81

2.80

2.79

2.78

2.77

2.76

3.060

3.045

3.030

3.015

3.000

2.985

2.970

2.955

2.940

3.360

3.345

3.330

3.315

3.300

3.285

3.270

3.255

3.240

I

= 1mA

I

= 1mA

I = 1mA

L

–25

0

25

50

75

125

–50

100

–25

0

25

50

75

125

–25

0

25

50

75

125

–50

100

–50

100

TEMPERATURE (°C)

1761 G52

1761 G09

1761 G11

LT1761-5

Output Voltage

LT1761-BYP, LT1761-SD

ADJ Pin Voltage

LT1761-1.2

Quiescent Current

250

225

200

175

150

125

100

75

5.08

5.06

5.04

5.02

5.00

4.98

4.96

4.94

4.92

1.240

1.235

1.230

1.225

1.220

1.215

1.210

1.205

1.200

I

= 1mA

T

= 25°C

= ∞

I

= 1mA

L

J

L

R

50

V

= V

IN

SHDN

25

= 0V

8

SHDN

0

–25

0

25

50

75

125

–50

100

–25

0

25

50

75

125

–50

100

0

1

2

3

4

5

6

7

9

10

TEMPERATURE (°C)

INPUT VOLTAGE (V)

1761 G12

1761 G10

1761 G10b

LT1761-1.5

Quiescent Current

LT1761-1.8

Quiescent Current

LT1761-2

Quiescent Current

200

175

150

125

100

75

200

175

150

125

100

75

200

175

150

125

100

75

T

= 25°C

= ∞

T

= 25°C

= ∞

T

= 25°C

R = ∞

L

J

L

J

L

J

R

50

V

= V

V

= V

V

= V

IN

SHDN

IN

SHDN

IN

SHDN

25

= 0V

8

= 0V

8

= 0V

8

SHDN

0

1

2

3

4

5

6

7

9

10

0

1

2

3

4

5

6

7

9

10

0

1

2

3

4

5

6

7

9

10

INPUT VOLTAGE (V)

1761 G53

1761 G18

1761 G19

1761sff

8

LT1761 Series

TYPICAL PERFORMANCE CHARACTERISTICS

LT1761-2.5

Quiescent Current

LT1761-2.8

Quiescent Current

LT1761-3

Quiescent Current

200

175

150

125

100

75

200

175

150

125

100

75

200

175

150

125

100

75

T

= 25°C

= ∞

T

= 25°C

= ∞

T

= 25°C

= ∞

J

L

J

L

J

L

R

50

V

= V

IN

V

= V

IN

V

= V

IN

SHDN

25

V

= 0V

8

V

= 0V

8

V

= 0V

8

SHDN

0

1

2

3

4

5

6

7

9

10

0

1

2

3

4

5

6

7

9

10

0

1

2

3

4

5

6

7

9

10

INPUT VOLTAGE (V)

1761 G13

1761 G54

1761 G14

LT1761-3.3

Quiescent Current

LT1761-5

Quiescent Current

LT1761-BYP, LT1761-SD

Quiescent Current

200

175

150

125

100

75

200

175

150

125

100

75

30

25

20

15

10

5

T

= 25°C

= ∞

T

= 25°C

= 250k

L

T

= 25°C

= ∞

J

L

J

L

R

I

= 5μA

L

V

= V

IN

SHDN

50

V

= V

V

= V

IN

SHDN

IN

SHDN

25

V

= 0V

8

= 0V

8

V

= 0V

SHDN

0

1

2

3

4

5

6

7

9

10

0

1

2

3

4

5

6

7

9

10

0

2

4

6

8

10 12 14 16 18 20

INPUT VOLTAGE (V)

1761 G15

1761 G16

1761 G17

LT1761-1.2

GND Pin Current

LT1761-1.5

GND Pin Current

LT1761-1.8

GND Pin Current

2.50

2.25

2.00

1.75

1.50

1.25

1.00

0.75

0.50

0.25

0

2.50

2.25

2.00

1.75

1.50

1.25

1.00

0.75

0.50

0.25

0

2.50

2.25

2.00

1.75

1.50

1.25

1.00

0.75

0.50

0.25

0

T

= 25°C

T

= 25°C

T

= 25°C

J

*FOR V

= 1.8V

*FOR V

= 1.2V

*FOR V

= 1.5V

OUT

R

L

= 12Ω

R

L

= 15Ω

R

L

= 18Ω

L

I

= 100mA*

I

= 100mA*

I

= 100mA*

R

L

= 24Ω

L

R

I

= 36Ω

L

R

L

= 30Ω

L

I

= 50mA*

I

= 50mA*

R

L

= 1.2k

L

R

L

= 1.5k

R = 1.8k

L

I = 1mA*

L

R

I

= 120Ω

R

I

= 150Ω

R

I

= 180Ω

L

I

= 1mA*

I

= 1mA*

= 10mA*

4

0

1

2

3

5

6

7

8

9

10

4

0

1

2

3

5

6

7

8

9

10

0

1

2

3

5

6

7

8

9

10

INPUT VOLTAGE (V)

1761 G17b

1761 G55

1761 G02

1761sff

9

LT1761 Series

TYPICAL PERFORMANCE CHARACTERISTICS

LT1761-2

GND Pin Current

LT1761-2.5

GND Pin Current

LT1761-2.8

GND Pin Current

2.50

2.25

2.00

1.75

1.50

1.25

1.00

0.75

0.50

0.25

0

2.50

2.25

2.00

1.75

1.50

1.25

1.00

0.75

0.50

0.25

0

2.50

2.25

2.00

1.75

1.50

1.25

1.00

0.75

0.50

0.25

0

T

= 25°C

T

= 25°C

T

= 25°C

J

*FOR V

= 2.8V

*FOR V

= 2.5V

*FOR V

= 2V

OUT

R

L

= 25Ω

L

R

L

= 28Ω

L

I

= 100mA

I

= 100mA

R

L

= 20Ω

L

I

= 100mA*

R

I

= 50Ω

R = 56Ω

L

I = 50mA*

L

R

= 40Ω

= 50mA*

L

= 50mA*

I

L

R

L

= 2k

R

L

= 2.5k

R = 2.8k

L

I = 1mA*

L

R

= 200Ω

= 10mA*

R

I

= 250Ω

R = 280Ω

L

I = 10mA*

L

I

= 1mA*

I

= 1mA*

I

= 10mA*

L

4

0

1

2

3

5

6

7

8

9

10

0

1

2

3

5

6

7

8

9

10

0

1

2

3

5

6

7

8

9

10

INPUT VOLTAGE (V)

1761 G04

1761 G20

1761 G56

LT1761-3

GND Pin Current

LT1761-3.3

GND Pin Current

LT1761-5

GND Pin Current

2.50

2.25

2.00

1.75

1.50

1.25

1.00

0.75

0.50

0.25

0

2.50

2.25

2.00

1.75

1.50

1.25

1.00

0.75

0.50

0.25

0

2.50

2.25

2.00

1.75

1.50

1.25

1.00

0.75

0.50

0.25

0

T

= 25°C

T

= 25°C

T = 25°C

J

*FOR V

= 3.3V

*FOR V

= 3V

*FOR V

= 5V

OUT

R

L

= 50Ω

L

I

= 100mA

R

L

= 30Ω

L

R

L

= 33Ω

L

I

= 100mA*

I

= 100mA*

R

L

= 100Ω

L

R

I

= 66Ω

L

R

L

= 60Ω

I

= 50mA*

L

= 50mA*

L

I

= 50mA*

R

I

= 5k

= 1mA*

L

R

L

= 3k

= 1mA*

R = 3.3k

L

I = 1mA*

L

R

= 500Ω

= 10mA*

R

= 300Ω

= 10mA*

R

I

= 330Ω

L

I

L

I

= 10mA*

L

4

0

1

2

3

5

6

7

8

9

10

0

1

2

3

5

6

7

8

9

10

0

1

2

3

5

6

7

8

9

10

INPUT VOLTAGE (V)

1761 G21

1761 G22

1761 G23

LT1761-BYP, LT1761-SD

GND Pin Current

SHDN Pin Threshold

GND Pin Current vs I_LOAD

(On to Off)

1.0

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0

2.50

2.25

2.00

1.75

1.50

1.25

1.00

0.75

0.50

0.25

0

2.50

2.25

2.00

1.75

1.50

1.25

1.00

0.75

0.50

0.25

0

I

= 1mA

V

= V

+ 1V

OUT(NOMINAL)

T

= 25°C

L

IN

J

*FOR V

= 1.22V

OUT

R

L

= 12.2Ω

L

I

= 100mA*

R

L

= 24.4Ω

L

I

= 50mA*

R

L

= 1.22k

L

R

L

= 122Ω

L

I

= 1mA*

I

= 10mA*

4

0

1

2

3

5

6

7

8

9

10

40

50 60 70 80 90 100

50

75 100 125

0

10 20 30

–50

0

25

–25

TEMPERATURE (°C)

INPUT VOLTAGE (V)

OUTPUT CURRENT (mA)

1761 G24

1761 G25

1761 G26

1761sff

10

LT1761 Series

TYPICAL PERFORMANCE CHARACTERISTICS

SHDN Pin Threshold

(Off to On)

SHDN Pin Input Current

1.0

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0

1.0

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0

1.4

1.2

1.0

0.8

0.6

0.4

0.2

0

V

= 20V

SHDN

I

= 100mA

L

I

= 1mA

L

50

TEMPERATURE (°C)

75 100 125

4

50

125

–50

0

25

0

1

2

3

5

6

7

8

9

10

–50

0

25

75

–25

100

TEMPERATURE (°C)

SHDN PIN VOLTAGE (V)

1761 G27

1761 G28

1761 G29

ADJ Pin Bias Current

Current Limit

100

90

80

70

60

50

40

30

20

10

0

350

300

250

200

150

100

50

350

300

250

200

150

100

50

V

= 7V

V

T

= 0V

IN

OUT

J

= 0V

= 25°C

0

–50

0

25

50

75 100 125

0

2

3

4

5

6

7

–50

0

25

50

75 100 125

–25

1

–25

TEMPERATURE (oC)

INPUT VOLTAGE (V)

TEMPERATURE (°C)

1761 G30

1761 G31

1761 G32

Reverse Output Current

Input Ripple Rejection

25.0

22.5

80

70

60

50

40

30

20

10

0

100

V

= 0V

IN

I = 100mA

L

T = 25°C

LT1761-BYP

LT1761-SD

J

= 1.22V (LT1761-BYP, -SD)

= 1.2V (LT1761-1.2)

= 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)

OUT

V

= V

+

90 V = 0V

IN

OUT(NOMINAL)

IN

LT1761-BYP

LT1761-5

1V + 50mV

RIPPLE

CURRENT FLOWS

RMS

V

20.0 OUT

80

70

60

50

40

30

20

10

0

C

= 0

INTO OUTPUT PIN

BYP

V

OUT

LT1761-1.2

V

= V

V

OUT

V

OUT

V

OUT

V

OUT

V

OUT

V

OUT

17.5

15.0

12.5

10.0

7.5

OUT

ADJ

(LT1761-BYP, -SD)

LT1761-1.5

C

= 10μF

LT1761-1.8

LT1761-2

LT1761-2.5

OUT

= 3.3V (LT1761-3.3)

= 5V (LT1761-5)

LT1761-2.8

LT1761-3

LT1761-BYP,-SD

5.0

C

= 1μF

OUT

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

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

LT1761-3.3

2.5

LT1761-5

0

10

100

1k

10k

100k

1M

–50

0

25

50

75 100 125

–25

4

0

1

2

3

5

6

7

8

9

10

FREQUENCY (Hz)

TEMPERATURE (°C)

OUTPUT VOLTAGE (V)

1761 G35

1761 G34

1761 G33

1761sff

11

LT1761 Series

TYPICAL PERFORMANCE CHARACTERISTICS

LT1761-5

Input Ripple Rejection

LT1761-BYP, LT1761-SD

Minimum Input Voltage

Input Ripple Rejection

80

70

60

50

40

30

20

10

0

80

70

60

50

40

30

20

10

0

2.5

2.0

1.5

1.0

0.5

0

C

= 0.01μF

BYP

C

= 1000pF

BYP

I

= 100mA

L

I

= 50mA

L

C

= 100pF

BYP

I

= 100mA

= V

V

= V

+

OUT (NOMINAL)

L

IN

V

+

OUT(NOMINAL)

1V + 0.5V RIPPLE

P-P

1V + 50mV

RIPPLE

AT f = 120Hz

RMS

C

= 10μF

I

= 50mA

OUT

L

–25

0

25

50

75

125

–50

100

10

100

1k

10k

100k

1M

–50

0

25

50

75 100 125

–25

FREQUENCY (Hz)

TEMPERATURE (°C)

1761 G36

1761 G37

1761 G38

Load Regulation

ΔI_L= 1mA to 50mA

Load Regulation

ΔI_L= 1mA to 100mA

0

–10

–20

–30

–40

–50

–60

–70

–80

–90

–100

LT1761-BYP, -SD, -1.2

LT1761-1.5

LT1761-BYP, -SD, -1.2

LT1761-1.5

LT1761-1.8

LT1761-2

–5

–10

–15

–20

–25

–30

–35

–40

LT1761-1.8

LT1761-2

LT1761-2.5

LT1761-2.8

LT1761-3

LT1761-2.5

LT1761-2.8

LT1761-3

LT1761-3.3

LT1761-5

–25

0

25

50

75

125

–25

0

25

50

75

125

–50

100

–50

100

TEMPERATURE (°C)

1761 G39

1761 G40

RMS Output Noise vs

Bypass Capacitor

Output Noise Spectral Density

10

1

10

1

140

120

100

80

C

L

= 10μF

OUT

LT1761-5

LT1761-3.3

LT1761-3

LT1761-2.8

LT1761-2.5

LT1761-3.3

I

= 100mA

LT1761-2.8,-3

f = 10Hz TO 100kHz

LT1761-2.5

LT1761-5

C

= 1000pF

BYP

C

BYP

= 100pF

LT1761-BYP,

-SD, 1.2

LT1761-BYP

60

LT1761-1.5

0.1

0.01

LT1761-1.8

LT1761-2

0.1

0.01

C

= 0.01μF

BYP

40

LT1761-1.8, -2

100

C

I

= 10μF

= 0

OUT

BYP

L

20

LT1761-1.5

C

OUT

I

= 10μF

= 100mA

LT1761-BYP, -1.2

= 100mA

L

0

10

100

1k

FREQUENCY (Hz)

10k

100k

10

100

1k

FREQUENCY (Hz)

10k

100k

10

1k

10k

C

(pF)

BYP

1761 G43

1761 G41

1761 G42

1761sff

12

LT1761 Series

TYPICAL PERFORMANCE CHARACTERISTICS

LT1761-5

10Hz to 100kHz Output Noise

C_BYP= 0pF

LT1761-5

10Hz to 100kHz Output Noise

C_BYP= 100pF

RMS Output Noise vs

Load Current (10Hz to 100kHz)

160

140

120

100

80

C

= 10μF

OUT

C

= 0

BYP

C

= 0.01μF

LT1761-5

V

OUT

100μV/DIV

LT1761-BYP

LT1761-5

60

40

1761 G46

1761 G45

C

I

= 10μF

1ms/DIV

C

I

= 10μF

1ms/DIV

OUT

L

OUT

L

20

= 100mA

LT1761-BYP

10

0

0.01

0.1

1

100

LOAD CURRENT (mA)

1761 G44

LT1761-5

10Hz to 100kHz Output Noise

C_BYP= 1000pF

LT1761-5

10Hz to 100kHz Output Noise

C_BYP= 0.01μF

V

OUT

V

OUT

100μV/DIV

1761 G46

1761 G48

C

L

= 10μF

1ms/DIV

OUT

C

= 10μF

1ms/DIV

OUT

I

= 100mA

I = 100mA

L

LT1761-5 Transient Response

C_BYP= 0pF

LT1761-5 Transient Response

C_BYP= 0.01μF

V

C

= 6V

V

C

= 6V

IN

0.2

0.1

0.04

0.02

0

= 10μF

OUT

0

–0.1

–0.2

–0.02

–0.04

100

50

0

100

50

0

800

TIME (μs)

80

0

400

1200

1600

2000

0

20 40 60

100 120 140 160 180 200

TIME (μs)

1761 G49

1761 G50

1761sff

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 ﬁlter 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 sufﬁcient.

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 ﬂow into the regulator and no reverse

voltage will appear at the load. The device will protect both

itself and the load.

BYP (Pins 3/4, Fixed/-BYP Devices): Bypass. The BYP

pin is used to bypass the reference of the LT1761 regula-

tors to achieve low noise performance from the regulator.

The BYP pin is clamped internally to 0.6V (one V ) from

BE

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

over a 10Hz

RMS

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 ampliﬁer.

This pin is internally clamped to 7V. It has a bias current

of 30nA which ﬂows 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.

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

ispulledlow.TheSHDNpincanbedriveneitherby5Vlogic

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

OUT(Pin5):Output.Theoutputsuppliespowertotheload.

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 volt-

age transients. See the Applications Information section

for more information on output capacitance and reverse

output characteristics.

pin must be connected to V . The device will not function

IN

if the SHDN pin is not connected. For the LT1761-BYP, the

SHDN pin is internally connected to V .

IN

1761sff

14

LT1761 Series

APPLICATIONS INFORMATION

The LT1761 series are 100mA low dropout regulators with

micropowerquiescentcurrentandshutdown.Thedevices

are capable of supplying 100mA at a dropout voltage of

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 Cur-

rent vs Temperature appear in the Typical Performance

Characteristics.

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 refer-

ence 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 ﬂow. 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.

The adjustable device is tested and speciﬁed with the ADJ

pin tied to the OUT pin for an output voltage of 1.22V.

Speciﬁcations 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

= 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 OUT to the BYP pin to lower output

voltage noise. A good quality low leakage capacitor is rec-

ommended. Thiscapacitorwillbypassthereferenceofthe

regulator, providing a low frequency noise pole. The noise

poleprovidedbythisbypasscapacitorwilllowertheoutput

voltage noise to as low as 20μV

with the addition of a

RMS

Adjustable Operation

0.01μF bypass capacitor. Using a bypass capacitor has the

added beneﬁt 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 ﬁnal 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.

TheadjustableversionoftheLT1761hasanoutputvoltage

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 cur-

rent, 30nA at 25°C, ﬂows 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

IN

OUT

ADJ

V

OUT

¥

´

µ

R2

R1

+

V

ꢀ 1ꢄ22V 1ꢁ

ꢁ I

ꢂ

R2

V

ꢃꢂ

ꢃ

IN

OUT

ADJ

¦

§

¶

R2

R1

LT1761

GND

V

ꢀ 1ꢄ22V

ADJ

I

ꢀ 30nA AT 25oC

ADJ

OUTPUT RANGE = 1.22V TO 20V

1761 F01

Figure 1. Adjustable Operation

1761sff

15

LT1761 Series

APPLICATIONS INFORMATION

Output Capacitance and Transient Response

and temperature coefﬁcients 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 tempera-

ture 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 avail-

able 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

capacitancechangeovertemperature.Capacitancechange

due to DC bias with X5R and X7R capacitors is better than

Y5VandZ5Ucapacitors,butcanstillbesigniﬁcantenough

to drop capacitor values below appropriate levels. Capaci-

tor DC bias characteristics tend to improve as component

casesizeincreases, butexpectedcapacitanceatoperating

voltage should be veriﬁed.

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 capaci-

tors. 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 capaci-

tor is recommended. With a 330pF bypass capacitor or

larger, a 3.3μF output capacitor is recommended. The

shaded region of Figure 2 deﬁnes the region over which

the LT1761 regulators are stable. The minimum ESR

needed is deﬁned by the amount of bypass capacitance

used, while the maximum ESR is 3Ω.

20

BOTH CAPACITORS ARE 16V,

1210 CASE SIZE, 10μF

0

X5R

–20

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 speciﬁed with EIA temperature char-

acteristic 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

–40

–60

Y5V

–80

–100

0

8

12 14

2

4

6

10

16

DC BIAS VOLTAGE (V)

1761 F03

Figure 3. Ceramic Capacitor DC Bias Characteristics

4.0

3.5

40

20

3.0

STABLE REGION

2.5

X5R

0

–20

2.0

–40

C

= 0

1.5

1.0

0.5

0

BYP

C

Y5V

= 100pF

BYP

–60

C

= 330pF

BYP

C

> 3300pF

BYP

–80

BOTH CAPACITORS ARE 16V,

1210 CASE SIZE, 10μF

–100

1

3

6 9 10

7 8

2

4

5

50

TEMPERATURE (°C)

100 125

–50 –25

0

25

75

OUTPUT CAPACITANCE (μF)

1761 F02

1761 F04

Figure 4. Ceramic Capacitor Temperature Characteristics

Figure 2. Stability

1761sff

16

LT1761 Series

APPLICATIONS INFORMATION

Voltage and temperature coefﬁcients 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 micro-

phone 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.

The ground pin current can be found by examining the

GND Pin Current curves in the Typical Performance Char-

acteristics section. Power dissipation will be equal to the

sum of the two components listed above.

TheLT1761seriesregulatorshaveinternalthermallimiting

designedtoprotectthedeviceduringoverloadconditions.

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 gener-

ated 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.

V

OUT

500μV/DIV

Table 1. Measured Thermal Resistance

1761 F05

LT1761-5

100ms/DIV

COPPER AREA

THERMAL RESISTANCE

C

LOAD

= 10μF

OUT

BYP

= 0.01μF

= 100mA

TOPSIDE*

BACKSIDE BOARD AREA (JUNCTION-TO-AMBIENT)

I

2

2500mm

125°C/W

130°C/W

135°C/W

150°C/W

2

1000mm

Figure 5. Noise Resulting from Tapping on a Ceramic Capacitor

2

225mm

Thermal Considerations

2

100mm

2

50mm

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:

*Device is mounted on topside.

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

1. Output current multiplied by the input/output voltage

differential: (I )(V – V ), and

OUT

IN

OUT

2. GND pin current multiplied by the input voltage:

(I )(V ).

GND

IN

1761sff

17

LT1761 Series

APPLICATIONS INFORMATION

and a maximum ambient temperature of 50°C, what will

the maximum junction temperature be?

Current limit protection and thermal overload protection

areintendedtoprotectthedeviceagainstcurrentoverload

conditionsattheoutputofthedevice.Fornormaloperation,

the junction temperature should not exceed 125°C.

The power dissipated by the device will be equal to:

I

(V

– V ) + I (V

)

OUT(MAX) IN(MAX)

OUT

GND IN(MAX)

The input of the device will withstand reverse voltages

of 20V. Current ﬂow 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.

where,

I

= 50mA

= 6V

OUT IN

OUT(MAX)

V

IN(MAX)

I

at (I

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

GND

So,

The output of the LT1761-X can be pulled below ground

withoutdamagingthedevice.Iftheinputisleftopencircuit

or grounded, the output can be pulled below ground by

20V. For ﬁxed voltage versions, the output will act like a

largeresistor,typically500korhigher,limitingcurrentﬂow

to typically less than 100μA. For adjustable versions, the

output will act like an open circuit; no current will ﬂow 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.

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

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

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.

Protection Features

The LT1761 regulators incorporate several protection

features which make them ideal for use in battery-pow-

ered 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.

1761sff

18

LT1761 Series

APPLICATIONS INFORMATION

In situations where the ADJ pin is connected to a resistor

dividerthatwouldpulltheADJpinaboveits7Vclampvolt-

age 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.

voltage may be held up while the input is either pulled

to ground, pulled to some intermediate voltage or is left

open circuit. Current ﬂow 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 cur-

rent 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.

In circuits where a backup battery is required, several

different input/output conditions can occur. The output

100

T = 25°C

LT1761-BYP

LT1761-SD

J

90 V = 0V

IN

CURRENT FLOWS

80

70

60

50

40

30

20

10

0

INTO OUTPUT PIN

= V

(LT1761-BYP, -SD)

LT1761-1.5

LT1761-1.2

V

OUT

ADJ

LT1761-1.8

LT1761-2

LT1761-2.5

LT1761-2.8

LT1761-3

LT1761-3.3

LT1761-5

4

0

1

2

3

5

6

7

8

9

10

OUTPUT VOLTAGE (V)

1761 F06

Figure 6. Reverse Output Current

1761sff

19

LT1761 Series

PACKAGE DESCRIPTION

S5 Package

5-Lead Plastic TSOT-23

(Reference LTC DWG # 05-08-1635)

0.62

MAX

0.95

REF

2.90 BSC

(NOTE 4)

1.22 REF

1.50 – 1.75

(NOTE 4)

2.80 BSC

1.4 MIN

3.85 MAX 2.62 REF

PIN ONE

RECOMMENDED SOLDER PAD LAYOUT

PER IPC CALCULATOR

0.30 – 0.45 TYP

5 PLCS (NOTE 3)

0.95 BSC

0.80 – 0.90

0.20 BSC

DATUM ‘A’

0.01 – 0.10

1.00 MAX

0.30 – 0.50 REF

1.90 BSC

0.09 – 0.20

(NOTE 3)

NOTE:

S5 TSOT-23 0302 REV B

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

1761sff

20

LT1761 Series

REVISION HISTORY ^{(Revision history begins at Rev F)}

REV

DATE

DESCRIPTION

PAGE NUMBER

F

5/10

Added MP-grade

2, 3

22

Added Typical Application

1761sff

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 representa-

tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.

21

LT1761 Series

TYPICAL APPLICATION

Noise Bypassing Provides Soft-Start

Startup Time

100

10

1

5V

AT 100mA

IN

OUT

BYP

V

IN

LT1761-5

10μF

1μF

C

BYP

5.4V TO 20V

OFF ON

SHDN

GND

1761 TA02a

0.1

10

100

1000

10000

C

(pF)

BYP

1761 TA02b

RELATED PARTS

PART NUMBER

DESCRIPTION

COMMENTS

Includes 2.5V Reference and Comparator

LT1120

125mA Low Dropout Regulator with 20μA I

Q

LT1121

150mA Micropower Low Dropout Regulator

700mA Micropower Low Dropout Regulator

30μA I , SOT-223 Package

Q

LT1129

50μA Quiescent Current

LT1175

500mA Negative Low Dropout Micropower Regulator

300mA Low Dropout Micropower Regulator with Shutdown

3A Low Dropout Regulator with 50μA I

45μA I , 0.26V Dropout Voltage, SOT-223 Package

Q

LT1521

15μA I , Reverse-Battery Protection

Q

LT1529

500mV Dropout Voltage

Q

LT1762 Series

LT1763 Series

LTC1928

LT1962 Series

LT1963

150mA, Low Noise, LDO Micropower Regulator

500mA, Low Noise, LDO Micropower Regulator

Doubler Charge Pump with Low Noise Linear Regulator

300mA, Low Noise, LDO Micropower Regulator

1.5A, Low Noise, Fast Transient Response LDO

3A, Low Noise, Fast Transient Response LDO

25μA Quiescent Current, 20μV

30μA Quiescent Current, 20μV

Noise

RMS

Low Output Noise: 60μV

(100kHz BW)

RMS

30μA Quiescent Current, 20μV

Noise

RMS

40μV

, SOT-223 Package

RMS

LT1764

, 340mV Dropout Voltage

RMS

LTC3404

High Efﬁciency Synchronous Step-Down Switching Regulator Burst Mode^®Operation, Monolithic, 100% Duty Cycle

1761sff

LT 0510 REV F • PRINTED IN USA

LinearTechnology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

22

●

(408) 432-1900 FAX: (408) 434-0507 www.linear.com


型号：	LT1761MPS5-5#TRM
厂家：	Linear
描述：	LT1761 - 100mA, Low Noise, LDO Micropower Regulators in TSOT-23; Package: SOT; Pins: 5; Temperature Range: -55°C to 125°C 光电二极管输出元件调节器
文件：	总22页 (文件大小：1159K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

LT1761MPS5-5#TRM [Linear]

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