LTC3025-1_技术文档

LTC3025-1/LTC3025-2/

LTC3025-3/LTC3025-4

500mA Micropower

VLDO Linear Regulators

FEATURES

DESCRIPTION

The LTC^®3025-X is a micropower, VLDO™ (very low drop-

out)linearregulatorwhichoperatesfrominputvoltagesas

low as 0.9V. The device is capable of supplying 500mA of

outputcurrentwithatypicaldropoutvoltageofonly85mV.

A BIAS supply is required to run the internal reference and

LDOcircuitrywhileoutputcurrentcomesdirectlyfromthe

IN supply for high efﬁciency regulation. The LTC3025-1

features an adjustable output with a low 0.4V reference

while the LTC3025-2, LTC3025-3, and LTC3025-4 have

ﬁxed 1.2V, 1.5V and 1.8V output voltages respectively.

n

Wide Input Voltage Range: 0.9V to 5.5V

n

Stable with Ceramic Capacitors

n

Very Low Dropout: 85mV at 500mA

n

Adjustable Output Range: 0.4V to 3.6V (LTC3025-1)

n

Fixed Output: 1.2V(LTC3025-2), 1.5V(LTC3025-3),

1.8V(LTC3025-4)

n

2% Voltage Accuracy over Temperature,

Supply and Load

Low Noise: 80μV

n

(10Hz to 100kHz)

RMS

n

BIAS Voltage Range: 2.5V to 5.5V

Fast Transient Recovery

The LTC3025-X’s low quiescent current makes it an ideal

choiceforuseinbattery-poweredsystems.For3-cellNiMH

and single cell Li-Ion applications, the BIAS voltage can

be supplied directly from the battery while the input can

come from a high efﬁciency buck regulator, providing a

high efﬁciency, low noise output.

Shutdown Disconnects Load from V and V

IN

BIAS

= 50μA Typ

= 0.01μA Typ

Low Operating Current: I = 4μA, I

Low Shutdown Current: I = 1μA, I

Output Current Limit

Thermal Overload Protection

Available in 6-Lead (2mm × 2mm) DFN Package

IN

BIAS

IN

BIAS

Other features include high output voltage accuracy,

excellent transient response, stability with ultralow ESR

ceramic capacitors as small as 1μF, short-circuit and

thermal overload protection and output current limiting.

The LTC3025-X is available in a tiny, low proﬁle (0.75mm)

6-lead DFN (2mm × 2mm) package.

APPLICATIONS

n

Low Power Handheld Devices

n

Low Voltage Logic Supplies

n

DSP Power Supplies

Cellular Phones

Portable Electronic Equipment

Handheld Medical Instruments

n

L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.

VLDO is a trademark of Linear Technology Corporation.

All other trademarks are the property of their respective owners.

Protected by U.S. Patents including 7224204, 7218082.

n

Post Regulator for Switching Supply Noise Rejection

TYPICAL APPLICATION

1.2V Output Voltage from 1.5V Input Supply

1MHz V_INSupply Rejection

50

V

I

= 1.2V

≤ 500mA

OUT

BIAS

OUT

SENSE

GND

45

40

35

30

25

20

15

10

5

C

= 10μF

OUT

0.1μF

1μF

Li-Ion

OR

3-CELL

NiMH

1.5V HIGH

EFFICIENCY

DC/DC

LTC3025-2

1.5V

IN

C

= 1μF

OUT

BUCK

0.1μF

OFF ON

SHDN

30251234 TA01

BIAS = 3.6V

OUT

I

= 100mA

= 300mA

OUT

V

= 1.2V

0

1.2

1.6 1.8 2.0

(V)

2.2 2.4 2.6

1.4

V

IN

30251234fc

30251234 TA01b

1

LTC3025-1/LTC3025-2/

LTC3025-3/LTC3025-4

ABSOLUTE MAXIMUM RATINGS

PIN CONFIGURATION

(Notes 1, 2)

TOP VIEW

V

, V to GND......................................... –0.3V to 6V

BIAS IN

SHDN to GND............................................... –0.3V to 6V

BIAS

GND

IN

1

2

3

6

5

4

SHDN

SENSE, ADJ to GND..................................... –0.3V to 6V

V

7

ADJ/SENSE*

OUT

........................................–0.3V to V + 0.3V or 6V

OUT

IN

Operating Junction Temperature Range

(Note 3).................................................. –40°C to 125°C

Storage Temperature Range................... –65°C to 125°C

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

DC6 PACKAGE

6-LEAD (2mm × 2mm) PLASTIC DFN

T

= 125°C, θ = 102°C/W, θ = 20°C/W

JMAX

JA JC

EXPOSED PAD (PIN 7) IS GND, MUST BE SOLDERED TO PCB

*ADJ FOR LTC3025-1, SENSE FOR LTC3025-2, LTC3025-3, LTC3025-4

ORDER INFORMATION

LEAD FREE FINISH

LTC3025EDC-1#PBF

LTC3025IDC-1#PBF

LTC3025EDC-2#PBF

LTC3025IDC-2#PBF

LTC3025EDC-3#PBF

LTC3025IDC-3#PBF

LTC3025EDC-4#PBF

LTC3025IDC-4#PBF

LEAD BASED FINISH

LTC3025EDC-1

TAPE AND REEL

PART MARKING*

LDDW

PACKAGE DESCRIPTION

TEMPERATURE RANGE

LTC3025EDC-1#TRPBF

LTC3025IDC-1#TRPBF

LTC3025EDC-2#TRPBF

LTC3025IDC-2#TRPBF

LTC3025EDC-3#TRPBF

LTC3025IDC-3#TRPBF

LTC3025EDC-4#TRPBF

LTC3025IDC-4#TRPBF

TAPE AND REEL

–40°C to 125°C

TEMPERATURE RANGE

–40°C to 125°C

6-Lead (2mm × 2mm) Plastic DFN

PACKAGE DESCRIPTION

LDDW

LDMK

LDQS

LDPQ

PART MARKING*

LDDW

LTC3025EDC-1#TR

LTC3025IDC-1#TR

LTC3025EDC-2#TR

LTC3025IDC-2#TR

LTC3025EDC-3#TR

LTC3025IDC-3#TR

LTC3025EDC-4#TR

LTC3025IDC-4#TR

6-Lead (2mm × 2mm) Plastic DFN

LTC3025IDC-1

LDDW

LTC3025EDC-2

LDMK

LTC3025IDC-2

LDMK

LTC3025EDC-3

LDQS

LTC3025IDC-3

LDQS

LTC3025EDC-4

LDPQ

LTC3025IDC-4

LDPQ

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/

ELECTRICAL CHARACTERISTICS

The l denotes the speciﬁcations which apply over the full operating

temperature range, otherwise speciﬁcations are at T_A= 25°C. V_IN= 1.5V, V_BIAS= 3.6V, C_OUT= 1μF, C_IN= 0.1μF, C_BIAS= 0.1μF

(all capacitors ceramic) unless otherwise noted.

PARAMETER

Operating Voltage (Note 4)

CONDITIONS

LTC3025-1

LTC3025-2

LTC3025-3

LTC3025-4

MIN

0.9

1.4

1.7

2.0

TYP

MAX

5.5

UNITS

l

V

IN

V

5.5

V

30251234fc

2

LTC3025-1/LTC3025-2/

LTC3025-3/LTC3025-4

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

temperature range, otherwise speciﬁcations are at T_A= 25°C. V_IN= 1.5V, V_BIAS= 3.6V, C_OUT= 1μF, C_IN= 0.1μF, C_BIAS= 0.1μF

(all capacitors ceramic) unless otherwise noted.

PARAMETER

CONDITIONS

LTC3025-1

LTC3025-2

LTC3025-3

LTC3025-4

MIN

2.5

2.7

3.0

3.3

TYP

MAX

5.5

2.5

10

80

5

UNITS

V

l

V

Operating Voltage (Note 4)

BIAS

V

Undervoltage Lockout

2.2

4

V

BIAS

Operating Current

I

= 10μA, V = 1.2V, LTC3025-1

OUT

μA

IN

OUT

= 0μA, LTC3025-2/LTC3025-3/LTC3025-4

= 10μA, V = 1.2V, LTC3025-1

4

IN

Operating Current

50

1

BIAS

OUT

= 0μA, LTC3025-2/LTC3025-3/LTC3025-4

Shutdown Current

V

SHDN

V

SHDN

= 0V

IN

Shutdown Current

0.01

1

BIAS

V

Regulation Voltage (Note 5)

1mA ≤ I

≤ 500mA, V

= 1.2V, 1.5V ≤ V ≤ 5V, LTC3025-1

0.395

0.392

0.4

0.405

0.408

V

ADJ

OUT

IN

l

= 1.2V, 1.5V ≤ V ≤ 5V, LTC3025-1

IN

V

Regulation Voltage (Note 5)

1mA ≤ I

≤ 500mA, 1.5V ≤ V ≤ 5V, LTC3025-2

1.185

1.176

1.2

1.215

1.224

V

SENSE

OUT

IN

V

1mA ≤ I

≤ 500mA, 1.7V ≤ V ≤ 5V, LTC3025-3

1.481

1.470

1.5

1.519

1.530

V

OUT

IN

1mA ≤ I

≤ 500mA, 2.0V ≤ V ≤ 5V, LTC3025-4

1.777

1.764

1.8

1.823

1.836

V

OUT

IN

I

ADJ Input Current

V

ADJ

= 0.45V, LTC3025-1

–50

0

50

nA

ADJ

OUT Load Regulation (Referred to ADJ Pin)

OUT Load Regulation

–0.35

mV

ΔI

= 1mA to 500mA, LTC3025-1

OUT

–1

–1.3

–1.5

mV

ΔI

= 1mA to 500mA, LTC3025-2

= 1mA to 500mA, LTC3025-3

= 1mA to 500mA, LTC3025-4

OUT

V

Line Regulation (Referred to ADJ Pin)

Line Regulation

V

OUT

= 1.5V to 5V, V

= 3.6V, V

= 1.2V,

0.07

mV

IN

BIAS

OUT

I

= 1mA, LTC3025-1

V

IN

V

IN

V

IN

= 1.5V to 5V, V

= 1.8V to 5V, V

= 2.1V to 5V, V

= 3.6V, I

= 1mA, LTC3025-2

= 1mA, LTC3025-3

= 1mA, LTC3025-4

0.21

0.26

0.32

mV

IN

BIAS

OUT

l

V

Line Regulation

V

= 1.5V, V

= 2.7V to 5V, V

= 1.2V, I = 1mA,

OUT

4.5

16.5

mV

BIAS

IN

BIAS

OUT

LTC3025-1

l

V

= 1.5V, V

= 1.8V, V

= 2.1V, V

= 2.7V to 5V, I

= 3.0V to 5V, I

= 3.3V to 5V, I

= 1mA, LTC3025-2

= 1mA, LTC3025-3

= 1mA, LTC3025-4

4.5

16.5

mV

BIAS

IN

BIAS

OUT

V

to V

Dropout Voltage (Notes 4, 6)

V

ADJ

= 2.8V, V = 1.5V, I = 500mA,

OUT

85

90

120

170

mV

IN

OUT

BIAS

IN

l

V

= 0.37V(LTC3025-1), V

= 1.15V(LTC3025-2)

SENSE

to V

Dropout Voltage (Notes 4, 6)

V

SENSE

= 3.1V, V = 1.7V, I

OUT

= 500mA,

130

185

mV

BIAS

IN

V

= 1.45V(LTC3025-3)

V

= 3.4V, V = 2.0V, I

OUT

= 500mA,

130

185

mV

BIAS

SENSE

IN

l

= 1.75V(LTC3025-4)

to V

Dropout Voltage (Note 4)

OUT

LTC3025-1

1.5

V

mA

BIAS

I

Continuous Output Current

Current Limit

500

OUT

V

SENSE

= 0V(LTC3025-1),

= 0V(LTC3025-2/LTC3025-3/LTC3025-4)

1130

80

ADJ

V

e Output Voltage Noise

n

f = 10Hz to 100kHz, I

= 300mA

μV

RMS

OUT

30251234fc

3

LTC3025-1/LTC3025-2/

LTC3025-3/LTC3025-4

ELECTRICAL CHARACTERISTICS

The l denotes the speciﬁcations which apply over the full operating

temperature range, otherwise speciﬁcations are at T_A= 25°C. V_IN= 1.5V, V_BIAS= 3.6V, C_OUT= 1μF, C_IN= 0.1μF, C_BIAS= 0.1μF

(all capacitors ceramic) unless otherwise noted.

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

V

l

V

SHDN Input High Voltage

SHDN Input Low Voltage

SHDN Input High Current

0.9

IH

IL

0.3

1

V

I

SHDN = 1.2V

SHDN = 0V

–1

μA

IH

I SHDN Input Low Current

L

1

Note 4: For the LTC3025-1, a regulated output voltage will only be available

when the minimum IN and BIAS operating voltages as well as the IN to

OUT and BIAS to OUT dropout voltages are all satisﬁed. For the

LTC3025-2/LTC3025-3/LTC3025-4 the minimum IN operating voltage

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: This IC includes overtemperature protection that is intended

to protect the device during momentary overload conditions. Junction

temperature will exceed 125°C when overtemperature protection is active.

Continuous operation above the speciﬁed maximum operating junction

temperature may impair device reliability.

assumes I

= 500mA. For correct regulation at I

< 500mA the

OUT

minimum IN operating voltage decreases to the maximum V

SENSE

Regulation Voltage as I

decreases to 0mA (i.e. V = 1.312V at I

INMIN OUT

OUT

= 250mA for the LTC3025-2).

Note 5: 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 6: Dropout voltage is minimum input to output voltage differential

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

Note 3: The LTC3025-X regulators are tested and speciﬁed under pulse

load conditions such that T ≈ T . The LTC3025E-X are guaranteed to

J

A

meet performance speciﬁcations from 0°C and 125°C. Speciﬁcations over

the –40°C to 125°C operating junction temperature range are assured by

design, characterization and correlation with statistical process controls.

The LTC3025I-X are guaranteed to meet performance speciﬁcations over

the full –40°C to 125°C operating junction temperature range.

output voltage will be equal to V – V

.

IN

DROPOUT

(T_A= 25°C unless otherwise noted)

TYPICAL PERFORMANCE CHARACTERISTICS

V_INto V_OUTDropout Voltage

vs I_OUT

Operating BIAS Current

vs Output Current

BIAS No Load Operating Current

500

450

400

350

300

250

200

150

100

50

120

100

80

70

60

50

V

= 2.8V

V

= 1.5V

BIAS

IN

OUT

= 1.4V

= 1.2V

T

= 125°C

A

T

= 25°C

80

60

A

125°C

–40°C

125°C

25°C

40

30

25°C

–40°C

T

A

= –40°C

40

20

0

20

10

0

0.1

1

I

100

0.01

1000

10

(mA)

2.5

3

3.5

4.5

5

5.5

4

0

50 100 150 200 250 300 350 400 450 500

(mA)

I

V

(V)

OUT

BIAS

30251234 G02

30251234 G03

30251234 G01

30251234fc

4

LTC3025-1/LTC3025-2/

LTC3025-3/LTC3025-4

(T_A= 25°C unless otherwise noted)

TYPICAL PERFORMANCE CHARACTERISTICS

V_INShutdown Current

Adjust Voltage vs Temperature

V_INNo Load Operating Current

14

12

405

7

6

V

= 5V

BIAS

OUT

V

= 5V

V

OUT

= 3.6V

BIAS

IN

= 0.8V

404

403

402

401

400

399

398

397

396

395

= 1.5V

I

= 10μA

10

8

5

4

3

2

1

0

125°C

–40°C

25°C

85°C

25°C

6

–40°C

4

85°C

2

0

0.5

1.5

2.5

3.5

(V)

5.5

4.5

–50

0

25

50

75 100 125

1.5

2.5

3.5

(V)

5.5

–25

0.5

4.5

V

TEMPERATURE (°C)

V

IN

30251234 G04

30251234 G06

30251234 G05

Burst Mode DC/DC Buck Ripple

Rejection

SHDN Threshold vs Temperature

Current Limit vs V_INVoltage

1000

900

800

700

600

500

400

300

200

100

0

1600

1400

1200

1000

V

IN

AC

100mV/DIV

V

= 5V

BIAS

V

= 2.5V

800

600

BIAS

V

OUT

AC

10mV/DIV

400

200

0

30251234 G09

V

C

I

= 1.8V

10μs/DIV

IN

OUT

= 1.5V

= 1μF

= 50mA

1

2

4

0

5

6

3

OUT

–50

0

25

50

75 100 125

–25

V

(V)

TEMPERATURE (°C)

IN

30251234 G08

30251234 G07

V_INRipple Rejection

vs Frequency

BIAS Ripple Rejection

vs Frequency

3MHz V_INSupply Rejection

50

45

40

35

30

25

20

15

10

5

70

60

70

60

C

= 10μF

= 1μF

OUT

C

= 10μF

C

= 10μF

OUT

50

40

30

20

10

0

50

40

30

20

10

0

C

OUT

C

= 1μF

OUT

C

= 1μF

1M

OUT

V

I

= 3.6V

V

I

= 3.6V

BIAS

IN

OUT

BIAS

IN

OUT

= 1.5V

= 1.2V

= 100mA

V

BIAS

V

OUT

= 3.6V

= 1.2V

I

= 100mA

OUT

= 300mA

OUT

= 1.2V

= 100mA

0

1.2

1.6 1.8 2.0

(V)

2.2 2.4 2.6

1k

10k

100k

10M

1.4

100

1M

1k

10k

100k

10M

100

V

FREQUENCY (Hz)

IN

30251234 G12

30251234 G10

30251234 G11

30251234fc

5

LTC3025-1/LTC3025-2/

LTC3025-3/LTC3025-4

(T_A= 25°C unless otherwise noted)

TYPICAL PERFORMANCE CHARACTERISTICS

V_INto V_OUTDropout Voltage

vs V_IN(25°C) LTC3025-1

V_INto V_OUTDropout Voltage

vs V_IN(90°C) LTC3025-1

Transient Response

0.300

0.725

0.250

0.225

0.200

0.175

0.150

0.125

0.100

0.075

0.050

0.025

0

0.300

0.725

0.250

0.225

0.200

0.175

0.150

0.125

0.100

0.075

0.050

0.025

0

BIAS = 2.7V

250mA

10mA

I

OUT

BIAS = 3.3V

BIAS = 3V

BIAS = 3.8V

V

OUT

AC

BIAS = 3.8V

BIAS = 5V

10mV/DIV

BIAS = 5V

BIAS = 3.3V

BIAS = 3V

BIAS = 2.7V

V

OUT

= 0.385

ADJ

V

OUT

= 0.385

ADJ

30251234 G13

V

C

= 1.5V

100μs/DIV

IN

I

= 500mA

I

= 500mA

= 1.2V

= 3.6V

= 1μF

OUT

BIAS

OUT

T

A

= 25°C

T = 90°C

A

1

2

2.5

3

3.5

4

4.5

1

2

2.5

3

3.5

4

4.5

1.5

V

(V)

V

(V)

IN

30251234 G14

30251234 G15

PIN FUNCTIONS

BIAS (Pin 1): BIAS Input Voltage. BIAS provides internal

power for LTC3025-X circuitry. The BIAS pin should be

locallybypassedtogroundiftheLTC3025-Xismorethana

few inches away from another source of bulk capacitance.

In general, the output impedance of a battery rises with

frequency, so it is usually advisable to include an input

bypass capacitor in battery-powered circuits. A capacitor

in the range of 0.01μF to 0.1μF is usually sufﬁcient.

SeetheApplicationsInformationsectionformoreinforma-

tion on output capacitance.

ADJ (Pin 5) LTC3025-1: Adjust Input. This is the input to

the error ampliﬁer. The ADJ pin reference voltage is 0.4V

referenced to ground. The output voltage range is 0.4V to

3.6V and is typically set by connecting ADJ to a resistor

divider from OUT to GND. See Figure 2.

SENSE (Pin 5) LTC3025-2, LTC3025-3, LTC3025-4: Out-

put Sense. The sense is the input to the resistor divider

driving the error ampliﬁer. Optimum regulation will be

obtained at the point where SENSE is connected to OUT.

The SENSE pin bias current is 10μA at the nominal rated

output voltage.

GND (Pin 2): Ground. Connect to a ground plane.

IN (Pin 3): Input Supply Voltage. The output load current

is supplied directly from IN. The IN pin should be locally

bypassed to ground if the LTC3025-X is more than a few

inches away from another source of bulk capacitance. In

general, the output impedance of a battery rises with fre-

quency,soitisusuallyadvisabletoincludeaninputbypass

capacitor when supplying IN from a battery. A capacitor

in the range of 0.1μF to 1μF is usually sufﬁcient.

SHDN (Pin 6): Shutdown Input, Active Low. This pin is

used to put the LTC3025-X into shutdown. The SHDN pin

current is typically less than 10nA. The SHDN pin cannot

be left ﬂoating and must be tied to a valid logic level (such

as BIAS) if not used.

OUT (Pin 4): Regulated Output Voltage. The OUT pin

supplies power to the load. A minimum ceramic output

capacitor of at least 1μF is required to ensure stability.

Larger output capacitors may be required for applications

with large transient loads to limit peak voltage transients.

Exposed Pad (Pin 7): Ground and Heat Sink. Must be

soldered to PCB ground plane or large pad for optimal

thermal performance.

30251234fc

6

LTC3025-1/LTC3025-2/

LTC3025-3/LTC3025-4

BLOCK DIAGRAM

LTC3025-1

LTC3025-2, LTC3025-3, LTC3025-4

BIAS

1

BIAS

1

6

SOFT-START

REFERENCE

IN

3

SHDN

6

2

SHDN 0.4V

+

–

SHDN 0.4V

+

–

6μA

R2

OUT

ADJ

OUT

GND

4

5

4

5

2

SENSE

R1

40k

80k (LTC3025-2)

110k (LTC3025-3)

140k (LTC3025-4)

30251234 BD

APPLICATIONS INFORMATION

Operation (Refer to Block Diagram)

Adjustable Output Voltage (LTC3025-1)

The LTC3025-X is a micropower, VLDO (very low dropout)

linear regulator which operates from input voltages as low

as 0.9V. The device provides a highly accurate output that

is capable of supplying 500mA of output current with a

typical dropout voltage of only 85mV. A single ceramic

capacitor as small as 1μF is all that is required for output

bypassing. A low reference voltage allows the LTC3025-1

output to be programmed to much lower voltages than

available in common LDOs (range of 0.4V to 3. 6V). The

LTC3025-2/LTC3025-3/LTC3025-4 have ﬁxed outputs of

1.2V, 1.5V and 1.8V respectively, eliminating the need for

an external resistor divider.

The output voltage is set by the ratio of two external resis-

tors as shown in Figure 2. The device servos the output

to maintain the ADJ pin voltage at 0.4V (referenced to

ground). Thus, the current in R1 is equal to 0.4V/R1. For

goodtransientresponse,stability,andaccuracy,thecurrent

300mA

I

OUT

0mA

V

OUT

AC

As shown in the Block Diagram, the BIAS input supplies

the internal reference and LDO circuitry while all output

currentcomesdirectlyfromtheINinputforhighefﬁciency

20mV/DIV

30251234 F01

V

C

= 1.5V

100μs/DIV

IN

regulation. The low quiescent supply currents I = 4μA,

IN

= 1.2V

= 3.6V

= 1μF

OUT

BIAS

OUT

I

= 50μA drop to I = 1μA, I

= 0.01μA typical in

shutdown making the LTC3025-X an ideal choice for use

BIAS

IN

BIAS

Figure 1. LTC3025-X Transient Response

in battery-powered systems.

The device includes current limit and thermal overload

protection. The fast transient response of the follower

output stage overcomes the traditional tradeoff between

dropout voltage, quiescent current and load transient

response inherent in most LDO regulator architectures.

TheLTC3025-Xalsoincludesovershootdetectioncircuitry

which brings the output back into regulation when going

from heavy to light output loads (see Figure 1).

R2

OUT

ADJ

GND

V

= 0.4V 1 +

OUT

(

)

R1

R2

R1

C

OUT

30251234 F02

Figure 2. Programming the LTC3025-1

30251234fc

7

LTC3025-1/LTC3025-2/

LTC3025-3/LTC3025-4

APPLICATIONS INFORMATION

in R1 should be at least 8μA, thus the value of R1 should

be no greater than 50k. The current in R2 is the current in

R1 plus the ADJ pin bias current. Since the ADJ pin bias

current is typically <10nA, it can be ignored in the output

voltage calculation. The output voltage can be calculated

using the formula in Figure 2. Note that in shutdown the

output is turned off and the divider current will be zero

Output Capacitance and Transient Response

The LTC3025-X is designed to be stable with a wide range

ofceramicoutputcapacitors.TheESRoftheoutputcapaci-

tor affects stability, most notably with small capacitors. A

minimum output capacitor of 1μF with an ESR of 0.05Ω or

less is recommended to ensure stability. The LTC3025-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

provideimprovedtransientresponseforlargerloadcurrent

changes. Note that bypass capacitors used to decouple

individual components powered by the LTC3025-X will

increase the effective output capacitor value. High ESR

tantalum and electrolytic capacitors may be used, but

a low ESR ceramic capacitor must be in parallel at the

output. There is no minimum ESR or maximum capacitor

size requirements.

once C

is discharged.

OUT

The LTC3025-1 operates at a relatively high gain of

–0.7μV/mA referred to the ADJ input. Thus a load cur-

rent change of 1mA to 500mA produces a –0.35mV drop

at the ADJ input. To calculate the change referred to the

outputsimplymultiplybythegainofthefeedbacknetwork

(i. e. ,1 + R2/R1). For example, to program the output for

1.2V choose R2/R1 = 2. In this example, an output current

change of 1mA to 500mA produces –0.35mV • (1 + 2) =

1.05mV drop at the output.

BecausetheADJpinisrelativelyhighimpedance(depend-

ing on the resistor divider used), stray capacitance at this

pin should be minimized (<10pF) to prevent phase shift

in the error ampliﬁer loop. Additionally, special attention

should be given to any stray capacitances that can couple

external signals onto the ADJ pin producing undesirable

output ripple. For optimum performance connect the ADJ

pin to R1 and R2 with a short PCB trace and minimize all

other stray capacitance to the ADJ pin.

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 di-

electrics used are Z5U, Y5V, X5R and X7R. The Z5U and

Y5V dielectrics are good for providing high capacitances

in a small package, but exhibit large voltage and tem-

perature coefﬁcients as shown in Figures 3 and 4. When

used with a 2V regulator, a 1μF Y5V capacitor can lose as

20

BOTH CAPACITORS ARE 1μF,

10V, 0603 CASE SIZE

0

X5R

–20

–40

–20

Y5V

–40

–60

Y5V

–60

–80

BOTH CAPACITORS ARE 1μF,

10V, 0603 CASE SIZE

–100

0

8

2

4

6

10

–50

0

25

50

75

–25

DC BIAS VOLTAGE (V)

TEMPERATURE (°C)

30251234 F03

30251234 F04

Figure 3. Ceramic Capacitor DC Bias Characteristics

Figure 4. Ceramic Capacitor Temperature Characteristics

30251234fc

8

LTC3025-1/LTC3025-2/

LTC3025-3/LTC3025-4

APPLICATIONS INFORMATION

much as 75% of its intial capacitance over the operating

temperature range. The X5R and X7R dielectrics result in

more stable characteristics and are usually more suitable

for use as the output capacitor. The X7R type has better

stabilityacrosstemperature,whiletheX5Rislessexpensive

and is available in higher values. In all cases, the output

capacitance should never drop below 0.4μF, or instability

or degraded performance may occur.

Calculating Junction Temperature

Example: Given an output voltage of 1.2V, an input voltage

of 1.8V to 3V, an output current range of 0mA to 100mA

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

(V

– V

)

OUT(MAX) IN(MAX)

OUT

Thermal Considerations

where:

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 the output current

multiplied by the input/output voltage differential:

I

= 100mA

= 3V

OUT(MAX)

V

IN(MAX)

So:

(I ) (V – V )

OUT

P = 100mA(3V – 1.2V) = 0.18W

OUT

IN

Note that the BIAS current is less than 500μA even under

heavy loads, so its power consumption can be ignored

for thermal calculations.

Even under worst-case conditions, the LTC3025-X’s BIAS

pin power dissipation is only about 1mW, thus can be ig-

nored.Assumingajunction-to-ambientthermalresistance

of 102°C/W, the junction temperature rise above ambient

will be approximately equal to:

The LTC3025-X has internal thermal limiting designed to

protectthedeviceduringmomentaryoverloadconditions.

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.

0.18W(102°C/W) = 18.4°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 + 18.4°C = 68.4°C

J

Short-Circuit/Thermal Protection

The LTC3025-X has built-in short-circuit current limiting

aswellasovertemperatureprotection.Duringshort-circuit

conditions,internalcircuitryautomaticallylimitstheoutput

currenttoapproximately1130mA.Athighertemperatures,

orincaseswhereinternalpowerdissipationcausesexces-

sive self heating on chip, the thermal shutdown circuitry

will shut down the LDO when the junction temperature

exceeds approximately 150°C. It will re enable the LDO

oncethejunctiontemperaturedropsbacktoapproximately

140°C. The LTC3025-X will cycle in and out of thermal

The LTC3025-X 2mm × 2mm DFN package is speciﬁed

as having a junction-to-ambient thermal resistance of

102°C/W, which assumes a minimal heat spreading cop-

per plane. The actual thermal resistance can be reduced

substantially by connecting the package directly to a good

2

heatspreadinggroundplane.Whensolderedto2500mm

double-sided 1 oz. copper plane, the actual junction-to-

ambient thermal resistance can be less than 60°C/W.

30251234fc

9

LTC3025-1/LTC3025-2/

LTC3025-3/LTC3025-4

APPLICATIONS INFORMATION

ON

shutdown without latch-up or damage until the overstress

SHDN

OFF

condition is removed. Long term overstress (T > 125°C)

J

should be avoided as it can degrade the performance or

1.2V

shorten the life of the part.

Soft-Start Operation

V

OUT

200mV/DIV

The LTC3025-X includes a soft-start feature to prevent

excessive current ﬂow during start-up. When the LDO is

enabled,thesoft-startcircuitrygraduallyincreasestheLDO

reference voltage from 0V to 0.4V over a period of about

600μs. There is a short 700μs delay from the time the

part is enabled until the LDO output starts to rise. Figure

5 shows the start-up and shutdown output waveform.

0V

30251234 F05

T

= 25°C

500μs/DIV

A

V

C

= 1.5V

IN

BIAS

OUT

= 3.6V

= 1μF

= 4Ω

R

LOAD

Figure 5. Output Start-Up and Shutdown

TYPICAL APPLICATION

High Efﬁciency 1.5V Step-Down Converter with Efﬁcient 1.2V VLDO Output

OFF ON

1

3

6

4

5

2

V

= 1.2V

≤ 500mA

OUT

BIAS

OUT

ADJ

GND

I

0.1μF

1μF

LTC3025-1

80.6k

2.2μH*

V

IN

4

1

3

5

2.7V

IN

V

SW

LTC3406-1.5

RUN

IN

C

4.7μF

CER

**

TO 5.5V

IN

40.2k

V

OUT

1.5V

SHDN

600mA

V

OUT

30251234 TA02

†

C

OUT

GND

10μF

CER

*MURATA LQH32CN2R2M33

**TAIYO YUDEN JMK212BJ475MG

^†TAIYO YUDEN JMK316BJ106ML

Efﬁciency vs Output Current

100

V

= 3.6V

IN

LTC3406-1.5

= 1.5V

V

OUT

90

80

70

60

50

40

LTC3025-1

= 1.2V

V

OUT

0.1

1

10

100

1000

OUTPUT CURRENT (mA)

30251234 TA03

30251234fc

10

LTC3025-1/LTC3025-2/

LTC3025-3/LTC3025-4

PACKAGE DESCRIPTION

DC Package

6-Lead Plastic DFN (2mm × 2mm)

(Reference LTC DWG # 05-08-1703)

R = 0.115

TYP

0.56 0.05

(2 SIDES)

0.38 0.05

4

6

0.675 0.05

2.50 0.05

1.15 0.05

0.61 0.05

(2 SIDES)

2.00 0.10

(4 SIDES)

PIN 1 BAR

PIN 1

PACKAGE

OUTLINE

TOP MARK

CHAMFER OF

(SEE NOTE 6)

EXPOSED PAD

(DC6) DFN 1103

3

1

0.25 0.05

0.50 BSC

0.75 0.05

0.200 REF

1.37 0.05

(2 SIDES)

1.42 0.05

(2 SIDES)

RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS

0.00 – 0.05

BOTTOM VIEW—EXPOSED PAD

NOTE:

1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WCCD-2)

2. DRAWING NOT TO SCALE

3. ALL DIMENSIONS ARE IN MILLIMETERS

4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE

MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE

5. EXPOSED PAD SHALL BE SOLDER PLATED

6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE

TOP AND BOTTOM OF PACKAGE

30251234fc

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.

11

LTC3025-1/LTC3025-2/

LTC3025-3/LTC3025-4

RELATED PARTS

PART NUMBER

DESCRIPTION

COMMENTS

LT^®1129

700mA, Micropower, LDO

V : 4.2V to 30V, V

OUT

= 3.75V, V = 0.40V, I = 50μA, I < 16μA,

IN

OUT(MIN) DO Q SD

V

= Adj, 3.3V, 5V, DD, SOT-223, S8, TO-220, TSSOP20 Packages

LT1175

500mA, Micropower, Negative LDO

V : –20V to –4.3V, V

OUT

Guaranteed Voltage Tolerance and Line/Load Regulation

= –3.8V, V = 0.50V, I = 45μA, I < 10μA,

IN

OUT(MIN) DO Q SD

V

= Adj, –5V, DD, SOT-223, S8, N8 Packages.

LT1185

LT1761

3A, Negative LDO

V : –35V to –4.2V, V = –2.40V, V = 0.80V, I = 2.5mA, I < 1μA,

OUT

IN

OUT(MIN)

DO

Q

SD

V

= Adj, TO-220 Package. Accurate Programmable Current Limit, Remote Sense

100mA, Low Noise Micropower, LDO

V : 1.8V to 20V, V

OUT

= 1.22V, V = 0.30V, I = 20μA, I < 1μA,

IN

OUT(MIN) DO Q SD

V

= Adj, 1.5V, 1.8V, 2V, 2.5V, 2.8V, 3V, 3.3V, 5V, ThinSOT^TMPackage.

Low Noise < 20μV

, Stable with 1μF Ceramic Capacitors

RMSP-P

LT1762

LT1763

150mA, Low Noise Micropower LDO

500mA, Low Noise Micropower LDO

V : 1.8V to 20V, V

OUT

= 1.22V, V = 0.30V, I = 25μA, I < 1μA,

IN

OUT(MIN) DO Q SD

V

= Adj, 2.5V, 3V, 3.3V, 5V, MS8 Package. Low Noise < 20μV

RMSP-P

V : 1.8V to 20V, V

OUT

= 1.22V, V = 0.30V, I = 30μA, I < 1μA,

DO Q SD

IN

OUT(MIN)

V

= 1.5, 1.8V, 2.5V, 3V, 3.3V, 5V, S8 Package. Low Noise < 20μV

RMSP-P

LT1764/LT1764A 3A, Low Noise, Fast Transient Response, LDO

V : 2.7V to 20V, V

OUT

“A” Version Stable with Ceramic Capacitors

= 1.21V, V = 0.34V, I = 1mA, I < 1μA,

IN

OUT(MIN) DO Q SD

V

= 1.8V, 2.5V, 3.3V, DD, TO-220 Packages. Low Noise < 40μV

,

RMSP-P

LTC1844

LT1962

150mA, Very Low Dropout LDO

V : 1.6V to 6.5V, V = 1.25V, V = 0.08V, I = 40μA, I < 1μA,

IN

V

OUT(MIN)

DO

Q

SD

= Adj, 1.5V, 1.8V, 2.5V, 2.8V, 3.3V, ThinSOT Package.

OUT

Low Noise < 30μV

, Stable with 1μF Ceramic Capacitors

RMSP-P

300mA, Low Noise Micropower LDO

V : 1.8V to 20V, V

OUT

= 1.22V, V = 0.27V, I = 30μA, I < 1μA,

IN

OUT(MIN) DO Q SD

V

= 1.5, 1.8V, 2.5V, 3V, 3.3V, 5V, MS8 Package. Low Noise < 20μV

RMSP-P

LT1963/LT1963A 1.5A, Low Noise, Fast Transient Response, LDO V : 2.1V to 20V, V

= 1.21V, V = 0.34V, I = 1mA, I < 1μA,

DO Q SD

IN

OUT(MIN)

V

= 1.5V, 1.8V, 2.5V, 3.3V, DD, SOT-223, S8, TO-220 Packages.

OUT

Low Noise < 40μV

, “A”Version Stable with Ceramic Capacitors

RMSP-P

LT1964

200mA, Low Noise Micropower, Negative LDO

V : –0.9V to –20V, V

= –1.21V, V = 0.34V, I = 30μA, I < 3μA,

IN

OUT(MIN) DO Q SD

V

= Adj, –5V, ThinSOT Package.

OUT

Low Noise < 30μV

, Stable with Ceramic Capacitors

RMSP-P

LT1965

LT3020

LT3023

1.1A, Low Noise, Low Dropout Linear Regulator 290mV Dropout Voltage, Low Noise: 40μV

, V : 1.8V to 20V, V : 1.2V to

RMS IN OUT

19.5V, Stable with Ceramic Caps, TO-220, DD, MSOP and 3 × 3 DFN Packages

100mA, Low Voltage, VLDO

V : 0.9V to 10V, V = 0.20V, V = 0.15V, I = 120μA, I < 3μA,

OUT

IN

OUT(MIN)

DO

Q

SD

V

= Adj, DFN, MS8 Package

Dual, 2 × 100mA, Low Noise Micropower, LDO

V : 1.8V to 20V, V

OUT

= 1.22V, V = 0.30V, I = 40μA, I < 1μA,

IN

OUT(MIN) DO Q SD

V

= Adj, DFN, MS Packages.

Low Noise < 20μV

, Stable with 1μF Ceramic Capacitors

RMSP-P

LT3024

Dual 100mA/500mA, Low Noise Micropower,

LDO

V : 1.8V to 20V, V

OUT

= 1.22V, V = 0.30V, I = 60μA, I < 1μA,

IN

OUT(MIN) DO Q SD

V

= Adj, DFN, TSSOP Packages.

Low Noise < 20μV

, Stable with 1μF Ceramic Capacitors

RMSP-P

LTC3025

LTC3026

300mA Micropower VLDO Linear Regulator

1.5A, Low Input Voltage VLDO Regulator

45mV Dropout Voltage, Low Noise: 80μV

, V : 0.9V to 5.5V, Low I = 54μA,

RMS IN Q

2mm × 2mm 6-Lead DFN Package

V : 1.14V to 3.5V (Boost Enabled), 1.14V to 5.5V (with External 5V Rail),

IN

DO

V

= 0.1V, I = 950μA, Stable with 10μF Ceramic Capacitors,

Q

DFN-10 and MSOP-10 Packages

LT3080/LT3080-1 1.1A, Parallelable, Low Noise, Low Dropout

Linear Regulator

300mV Dropout Voltage (2-supply operation), Low Noise: 40μV

, V : 1.2V to

OUT

RMS IN

36V, V : 0V to 35.7V, Current-Based Reference with 1-Resistor V

Set; Directly

OUT

Parallelable (No Op Amp Required), Stable with Ceramic Caps, TO-220, SOT-223,

MSOP and 3 × 3 DFN Packages; “–1” Version Has Integrated Internal Ballast

Resistor

ThinSOT is a trademark of Linear Technology Corporation.

30251234fc

LT 1008 REV C • PRINTED IN USA

LinearTechnology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

12

●

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


型号：	LTC3025-1
厂家：	Linear
描述：	500mA Micropower VLDO Linear Regulators 500毫安微VLDO线性稳压器稳压器
文件：	总12页 (文件大小：183K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

LTC3025-1 [Linear]

相关型号：

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LTC3025-1_1

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LTC3025-2

LTC3025-2_15

LTC3025-3

LTC3025-3_15

LTC3025-4

LTC3025-4_15

LTC3025EDC

LTC3025EDC#PBF

LTC3025EDC#TRMPBF