Datasheet LT1529-3.3, LT1529, LT1529-5 Datasheet (Linear Technology)

1

LT1529

LT1529-3.3/LT1529-5

3A Low Dropout Regulators

with Micropower

Quiescent Current

and Shutdown

The LT®1529/LT1529-3.3/LT1529-5 are 3A low dropout
regulators with micropower quiescent current and shut­down. The devices are capable of supplying 3A of output
current with a dropout voltage of 0.6V. Designed for use
in battery-powered systems, the low quiescent current,
50µA operating and 16µA in shutdown, make them an
ideal choice. The quiescent current is well controlled; it
does not rise in dropout as it does with many other low
dropout PNP regulators.

Other features of the LT1529 /LT1529-3.3/LT1529-5 in­clude the ability to operate with small output capacitors.
They are stable with only 3.3µF on the output while most
older devices require between 10µF and 100µF for stabil-
ity. Small ceramic capacitors can be used, enhancing
manufacturabiltiy. Also the input may be connected to
voltages lower than the output voltage, including negative
voltages, without reverse current flow from output to
input. This makes the LT1529/LT1529-3.3/LT1529-5 ideal
for backup power situations where the output is held high
and the input is at ground or reversed. Under these
conditions, only 16µA will flow from the OUTPUT pin to
ground. The devices are available in 5-lead TO-220 and
5-lead DD packages.

■

Dropout Voltage: 0.6V at I

OUT

= 3A

■

Output Current: 3A

■

Quiescent Current: 50µA

■

No Protection Diodes Needed

■

Adjustable Output from 3.8V to 14V

■

3.3V and 5V Fixed Output Voltages

■

Controlled Quiescent Current in Dropout

■

Shutdown IQ = 16µA

■

Stable with 3.3µF Output Capacitor

■

Reverse Battery Protection

■

No Reverse Current

■

Thermal Limiting

OUTPUT CURRENT (A)

0

0

DROPOUT VOLTAGE (V)

0.1

0.2

0.3

0.4

0.6

0.5

1.0 1.5 2.0

LT1529 • TA02

2.5 3.0

0.5

Dropout Voltage

5V Supply with Shutdown

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

■

High Efficiency Regulator

■

Regulator for Battery-Powered Systems

■

Post Regulator for Switching Supplies

■

5V to 3.3V Logic Regulator

+

V

IN

VIN > 5.5V

3.3µF
SOLID
TANT

5V
3A

1

2

3

LT1529 • TA01

5

4

OUTPUT

SENSE

LT1529-5

SHDN

GND

V

SHDN

(PIN 4)

<0.25

>2.8

NC

OUTPUT

OFF

ON
ON

FEATURES

DESCRIPTIO

U

APPLICATIO S

U

TYPICAL APPLICATIO

U

2

LT1529
LT1529-3.3/LT1529-5

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

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

Operating Junction Temperature Range

Commercial .......................................... 0°C to 125°C

Industrial ......................................... – 45°C to 125°C

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

*For applications requiring input voltage ratings greater than 15V, contact

the factory.

A

U
G

W

A

WUW

ARB

S

O

LUTEXI TIS

Input Voltage ...................................................... ±15V*

OUTPUT Pin Reverse Current .............................. 10mA

SENSE Pin Current .............................................. 10mA

ADJ Pin Current ................................................... 10mA

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

SHDN Pin Input Current (Note 2) .......................... 5mA

WU

U

PACKAGE

/

O

RDER I FOR ATIO

ORDER PART

NUMBER

LT1529CQ
LT1529CQ-3.3
LT1529CQ-5
LT1529IQ
LT1529IQ-3.3
LT1529IQ-5

*PIN 2 = SENSE FOR LT1529-3.3/LT1529-5

= ADJ FOR LT1529

ORDER PART

NUMBER

LT1529CT
LT1529CT-3.3
LT1529CT-5
LT1529IT
LT1529IT-3.3
LT1529IT-5

*PIN 2 = SENSE FOR LT1529-3.3/LT1529-5
= ADJ FOR LT1529

Consult factory for Military grade parts.

T

JMAX

= 125°C, θJA ≈ 30°C/W

PARAMETER CONDITIONS MIN TYP MAX UNITS

Regulated Output Voltage LT1529-3.3 VIN = 3.8V, I

OUT

= 1mA, TJ = 25°C 3.250 3.300 3.350 V

(Note 4) 4.3V < V

IN

< 15V, 1mA < I

OUT

< 3A ● 3.200 3.300 3.400 V

LT1529-5 VIN = 5.5V, I

OUT

= 1mA, TJ = 25°C 4.925 5.000 5.075 V

6V < V

IN

< 15V, 1mA < I

OUT

< 3A ● 4.850 5.000 5.150 V

LT1529 (Note 5) VIN = 4.3V, I

OUT

= 1mA, TJ = 25°C 3.695 3.750 3.805 V

4.8V < V

IN

< 15V, 1mA < I

OUT

< 3A ● 3.640 3.750 3.860 V

Line Regulation LT1529-3.3 ∆VIN = 3.8V to 15V, I

OUT

= 1mA ● 1.5 10 mV

LT1529-5 ∆VIN = 5.5V to 15V, I

OUT

= 1mA ● 1.5 10 mV

LT1529 (Note 5) ∆VIN = 4.3V to 15V, I

OUT

= 1mA ● 1.5 10 mV

Load Regulation LT1529-3.3 ∆I

LOAD

= 1mA to 3A, VIN = 4.3V, TJ = 25°C520mV

∆I

LOAD

= 1mA to 3A, VIN = 4.3V ● 12 30 mV

LT1529-5 ∆I

LOAD

= 1mA to 3A, VIN = 6V, TJ = 25°C520mV

∆I

LOAD

= 1mA to 3A, VIN = 6V ● 12 30 mV

LT1529 (Note 5) ∆I

LOAD

= 1mA to 3A, VIN = 4.8V, TJ = 25°C520mV

∆I

LOAD

= 1mA to 3A, VIN = 4.8V ● 12 30 mV

Dropout Voltage I

LOAD

= 10mA, TJ = 25°C 110 180 mV

(Note 6) I

LOAD

= 10mA ● 250 mV

I

LOAD

= 100mA, TJ = 25°C 200 300 mV

I

LOAD

= 100mA ● 400 mV

E

LECTRICAL C CHARA TERIST

ICS

V

IN

SHDN
GND
SENSE/ADJ*
OUTPUT

Q PACKAGE

5-LEAD PLASTIC DD PAK

TAB IS

GND

FRONT VIEW

5
4
3
2
1

T PACKAGE

5-LEAD PLASTIC TO-220

FRONT VIEW

TAB IS

GND

5
4
3
2
1

V

IN

SHDN
GND
SENSE/ADJ*
OUTPUT

(Note 1)

T

JMAX

= 125°C, θJA ≈ 50°C/W

The ● denotes specifications which apply over the operating temperature range, otherwise specificatons are at TA = 25°C. (Note 3)

3

LT1529

LT1529-3.3/LT1529-5

E

LECTRICAL C CHARA TERIST

ICS

PARAMETER CONDITIONS MIN TYP MAX UNITS

Dropout Voltage I

LOAD

= 700mA, TJ = 25°C 320 430 mV

(Note 6) I

LOAD

= 700mA ● 550 mV

I

LOAD

= 1.5A, TJ = 25°C 430 550 mV

I

LOAD

= 1.5A ● 700 mV

I

LOAD

= 3A, TJ = 25°C 600 750 mV

I

LOAD

= 3A ● 950 mV

GND Pin Current I

LOAD

= 0mA, TJ = 25°C 50 100 µA

(Note 7) I

LOAD

= 0mA, TJ = 125°C (Note 8) 400 µA

I

LOAD

= 100mA, TJ = 25°C 0.6 1.0 mA

I

LOAD

= 100mA, TJ = 125°C (Note 8) 1.0 mA

I

LOAD

= 700mA ● 5.5 12 mA

I

LOAD

= 1.5A ● 20 40 mA

I

LOAD

= 3A ● 80 160 mA

ADJ Pin Bias Current (Notes 5, 9) TJ = 25°C 150 300 nA
Shutdown Threshold V

OUT

= Off to On ● 1.20 2.8 V

V

OUT

= On to Off ● 0.25 0.75 V

SHDN Pin Current (Note 10) V

SHDN

= 0V ● 4.5 10 µA

Quiescent Current in Shutdown V

IN

= V

OUT

(Nominal) + 1V, V

SHDN

= 0V ● 15 30 µA

(Note 11)
Ripple Rejection V

IN

– V

OUT

= 1V (Avg), V

RIPPLE

= 0.5V

P-P

,5062dB

f

RIPPLE

= 120Hz, I

LOAD

= 1.5A

Current Limit V

IN

– V

OUT

= 7V, TJ = 25°C5A

VIN = V

OUT

(Nominal) + 1.5V, ∆V

OUT

= –0.1V ● 3.2 4.7 A

Input Reverse Leakage Current VIN = –15V, V

OUT

= 0V ● 1.0 mA

Reverse Output Current (Note 12) LT1529-3.3 V

OUT

= 3.3V, VIN = 0V 16 µA

LT1529-5 V

OUT

= 5V, VIN = 0V 16 µA

LT1529 (Note 6) V

OUT

= 3.8V, VIN = 0V 16 µA

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

Note 2: The SHDN pin input voltage rating is required for a low impedance
source. Internal protection devices connected to the SHDN pin will turn on
and clamp the pin to approximately 7V or –0.6V. This range allows the use
of 5V logic devices to drive the pin directly. For high impedance sources or
logic running on supply voltages greater than 5.5V, the maximum current
driven into the SHDN pin must be limited to less than 5mA.

Note 3: The device is tested under pulse load conditions such that T

J

= TA.

Note 4: Operating conditions are limited by maximum junction
temperature. The regulated output voltage specification will not apply for
all possible combinations of input voltage and output current. When
operating at maximum input voltage, the output current range must be
limited. When operating at maximum output current the input voltage
range must be limited.

Note 5: The LT1529 is tested and specified with the ADJ pin connected to
the OUTPUT pin.

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

IN

– V

DROPOUT

).

Note 7: GND pin current is tested with V

IN

= V

OUT

(nominal) and a current
source load. This means that the device is tested while operating in its
dropout region. This is the worst-case GND pin current. The GND pin
current will decrease slightly at higher input voltages.

Note 8: GND pin current will rise at TJ > 75°C. This is due to internal
circuitry designed to compensate for leakage currents in the output
transistor at high temperatures. This allows quiescent current to be
minimized at lower temperatures, yet maintain output regulation at high
temperatures with light loads. See quiescent current curve in typical
performance characteristics.

Note 9: ADJ pin bias current flows into the ADJ pin.
Note 10: SHDN pin current at V

SHDN

= 0V flows out of the SHDN pin.

Note 11: Quiescent current in shutdown is equal to the sum total of the
SHDN pin current (5µA) and the GND pin current (10µA).

Note 12: Reverse output current is tested with the V

IN

pin grounded and
the OUTPUT pin forced to the rated output voltage. This current flows into
the OUTPUT pin and out of the GND pin.

The ● denotes specifications which apply over the operating temperature range, otherwise specificatons are at TA = 25°C. (Note 3)

4

LT1529
LT1529-3.3/LT1529-5

Quiescent Current

CCHARA TERIST

ICS

UW

ATYPICA

LPER

F

O

R

C

E

TEMPERATURE (°C)

–50

0

QUIESCENT CURRENT (µA)

100

250

0

50

75

LT1529 • G03

50

200

150

–25

25

100

125

VIN = 6V
R

L

=

∞

V

SHDN

= OPEN

V

SHDN

= 0V

Guaranteed Dropout Voltage

Dropout Voltage

TEMPERATURE (°C)

–50

DROPOUT VOLTAGE (V)

0.7

A

B

C
D

E

F

25

LT1529 • G02

0.4

0.2

–25 0 50

0.1

0

0.8

0.6

0.5

0.3

75 100 125

A: I

LOAD

= 3A

B: I

LOAD

= 1.5A

C: I

LOAD

= 700mA

D: I

LOAD

= 300mA

E: I

LOAD

= 100mA

F: I

LOAD

= 10mA

LT1529
Quiescent Current

INPUT VOLTAGE (V)

0

QUIESCENT CURRENT (µA)

150

200

250

8

LT1529 • G06

100

50

125

175

225

75

25

0

2

4

6

19

3

5

7

10

I

LOAD

= 0

R

L

= ∞

V

OUT

= V

ADJ

V

SHDN

= OPEN (HIGH)

V

SHDN

= 0V

LT1529-3.3
Quiescent Current

INPUT VOLTAGE (V)

0

QUIESCENT CURRENT (µA)

150

200

250

8

LT1529 • G04

100

50

125

175

225

75

25

0

2

4

6

19

3

5

7

10

I

LOAD

= 0

R

L

= ∞

V

SHDN

= OPEN (HIGH)

V

SHDN

= 0V

LT1529-5
Quiescent Current

INPUT VOLTAGE (V)

0

QUIESCENT CURRENT (µA)

150

200

250

8

LT1529 • G05

100

50

125

175

225

75

25

0

2

4

6

19

3

5

7

10

I

LOAD

= 0

R

L

= ∞

V

SHDN

= OPEN (HIGH)

V

SHDN

= 0V

LT1529-3.3
Output Voltage

TEMPERATURE (°C)

–50

OUTPUT VOLTAGE (V)

3.375

25

LT1529 • G07

3.300

3.250

–25 0 50

3.225

3.200

3.400

3.350

3.325

3.275

75 100 125

I

LOAD

= 1mA

LT1529-5
Output Voltage

TEMPERATURE (˚C)

–50

OUTPUT VOLTAGE (V)

5.075

25

LT1529 • G08

5.000

4.950

–25 0 50

4.925

4.900

5.100

5.050

5.025

4.975

75 100 125

I

LOAD

= 1mA

LT1529
ADJ Pin Voltage

TEMPERATURE (°C)

–50

ADJ PIN VOLTAGE (V)

3.825

25

LT1529 • G09

3.750

3.700

–25 0 50

3.675

3.650

3.850

3.800

3.775

3.725

75 100 125

I

LOAD

= 1mA

OUTPUT CURRENT (A)

0

0

DROPOUT VOLTAGE (V)

0.2

0.3

0.4

0.5

0.6

0.7

0.5

1.0

1.5 2.0

LT1529 • G01

2.5

0.8

0.9

1.0

0.1

3.0

= TEST POINT

5

LT1529

LT1529-3.3/LT1529-5

CCHARA TERIST

ICS

UW

ATYPICA

LPER

F

O

R

C

E

LT1529-3.3
GND Pin Current

LT1529-5
GND Pin Current

LT1529
GND Pin Current

LT1529-5
GND Pin Current

GND Pin Current

SHDN Pin Threshold
(Off-to-On)

LT1529-3.3
GND Pin Current

LT1529
GND Pin Current

INPUT VOLTAGE (V)

0

GND PIN CURRENT (mA)

60

80

100

8

LT1529 • G15

40

20

50

70

90

30

10

0

2

4

6

19

3

5

7

10

TJ = 25°C
V

OUT

= V

ADJ

*FOR V

OUT

= 3.75V

R

LOAD

= 1.25Ω

I

LOAD

= 3A*

R

LOAD

= 2.5Ω

I

LOAD

= 1.5A*

R

LOAD

= 5.3Ω

I

LOAD

= 700mA*

OUTPUT CURRENT (A)

0

0

GND PIN CURRENT (mA)

20

30

40

50

60

70

0.5

1.0

1.5 2.0

LT1529 • G16

2.5

80

90

100

10

3.0

VIN = 3.75V (LT1529)
V

IN

= 3.3V (LT1529-3.3)

V

IN

= 5V (LT1529-5)
DEVICE IS OPERATING
IN DROPOUT

TJ = 125°C

T

J

= –50°C

TJ = 25°C

SHDN Pin Threshold
(On-to-Off)

TEMPERATURE (°C)

–50

0

SHDN THRESHOLD (V)

0.2

0.6

0.8

1.0

2.0

1.4

0

50

75

LT1529 • G17

0.4

1.6

1.8

1.2

–25

25

100

125

I

LOAD

= 1mA

TEMPERATURE (°C)

–50

0

SHDN THRESHOLD (V)

0.2

0.6

0.8

1.0

2.0

1.4

0

50

75

LT1529 • G18

0.4

1.6

1.8

1.2

–25

25

100

125

I

LOAD

= 3A

I

LOAD

= 1mA

INPUT VOLTAGE (V)

0

GND PIN CURRENT (mA)

3.0

4.0

5.0

8

LT1529 • G10

2.0

1.0

2.5

3.5

4.5

1.5

0.5
0

2

4

6

19

3

5

7

10

TJ = 25°C
V

OUT

= V

SENSE

*FOR V

OUT

= 3.3V

R

LOAD

= 6.6Ω

I

LOAD

= 500mA*

R

LOAD

= 11Ω

I

LOAD

= 300mA*

R

LOAD

= 33Ω

I

LOAD

= 100mA*

R

LOAD

= 330Ω

I

LOAD

= 10mA*

INPUT VOLTAGE (V)

0

GND PIN CURRENT (mA)

60

80

100

8

LT1529 • G13

40

20

50

70

90

30

10

0

2

4

6

19

3

5

7

10

TJ = 25°C
V

OUT

= V

SENSE

R

LOAD

= 1.1Ω

I

LOAD

= 3A*

R

LOAD

= 2.2Ω

I

LOAD

= 1.5A*

R

LOAD

= 4.7Ω

I

LOAD

= 700mA*

*FOR V

OUT

= 3.3V

INPUT VOLTAGE (V)

0

GND PIN CURRENT (mA)

60

80

100

8

LT1529 • G14

40

20

50

70

90

30

10

0

2

4

6

19

3

5

7

10

TJ = 25°C
V

OUT

= V

SENSE

*FOR V

OUT

= 5V

R

LOAD

= 1.7Ω

I

LOAD

= 3A*

R

LOAD

= 3.3Ω

I

LOAD

= 1.5A*

R

LOAD

= 7.1Ω

I

LOAD

= 700mA*

INPUT VOLTAGE (V)

0

GND PIN CURRENT (mA)

3.0

4.0

5.0

8

LT1529 • G11

2.0

1.0

2.5

3.5

4.5

1.5

0.5
0

2

4

6

19

3

5

7

10

TJ = 25°C
V

OUT

= V

SENSE

*FOR V

OUT

= 5V

R

LOAD

= 10Ω

I

LOAD

= 500mA*

R

LOAD

= 16.6Ω

I

LOAD

= 300mA*

R

LOAD

= 500Ω

I

LOAD

= 10mA*

R

LOAD

= 50Ω

I

LOAD

= 100mA*

INPUT VOLTAGE (V)

0

GND PIN CURRENT (mA)

3.0

4.0

5.0

8

LT1529 • G12

2.0

1.0

2.5

3.5

4.5

1.5

0.5
0

2

4

6

19

3

5

7

10

TJ = 25°C
V

OUT

= V

ADJ

*FOR V

OUT

=

3.75V

R

LOAD

= 7.5Ω

I

LOAD

= 500mA*

R

LOAD

= 12.5Ω

I

LOAD

= 300mA*

R

LOAD

= 375Ω

I

LOAD

= 10mA*

R

LOAD

= 38Ω

I

LOAD

= 100mA*

6

LT1529
LT1529-3.3/LT1529-5

CCHARA TERIST

ICS

UW

ATYPICA

LPER

F

O

R

C

E

SHDN Pin Current ADJ Pin Bias Current

TEMPERATURE (°C)

–50

0

SHDN PIN CURRENT (µA)

1

3

4

5

10

7

0

50

75

LT1529 • G19

2

8

9

6

–25

25

100

125

V

SHDN

= 0V

SHDN Pin Input Current

SHDN PIN VOLTAGE (V)

0

0

SHDN PIN INPUT CURRENT (mA)

5

15

20

25

2

4

59

LT1529 • G20

10

13

6

7

8

TEMPERATURE (°C)

–50

0

ADJ PIN BIAS CURRENT (nA)

50

150

200

250

500

350

0

50

75

LT1529 • G21

100

400

450

300

–25

25

100

125

V

ADJ

= V

OUT

= 3.75V

Current LimitCurrent LimitReverse Output Current

TEMPERATURE (°C)

–50

OUTPUT CURRENT (µA)

100

125

150

25 75

LT1529 • G22

75

50

–25 0

50 100 125

25

0

INPUT VOLTAGE (V)

0

SHORT-CIRCUIT CURRENT (A)

4

5

6

35

LT1529 • G23

3

2

12

467

1

0

V

OUT

= 0V

TEMPERATURE (°C)

–50

SHORT-CIRCUIT CURRENT (A)

4

5

6

25 75

LT1529 • G24

3

2

–25 0

50 100 125

1

0

VIN = 7V
V

OUT

= 0V

Reverse Output Current

OUTPUT VOLTAGE (V)

0

OUTPUT CURRENT (µA)

60

80

100

8

LT1529 • G25

40

20

50

70

90

30

10

0

2

4

6

19

3

5

7

10

LT1529

LT1529-5

LT1529-3.3

TJ = 25°C, VIN = 0V
V

OUT

= V

SENSE

(LT1529-3.3/LT1529-5)
V

OUT

= V

ADJ

(LT1529)
CURRENT FLOWS
INTO DEVICE

Ripple Rejection

TEMPERATURE (°C)

–50

56

58

62

25 75

LT1529 • G26

54

52

–25 0

50 100 125

50

48

60

RIPPLE REJECTION (dB)

(VIN – V

OUT

)AVG = 1V

V

RIPPLE

= 0.5V

P-P

I

LOAD

= 1.5A

f = 120Hz

Ripple Rejection

FREQUENCY (Hz)

20

RIPPLE REJECTION (dB)

40

60
50

80

100

10

30

70

90

10 1k 10k 100k

LT1529 • G27

0

100

I

OUT

= 1.5A

V

IN

= V

OUT

(NOMINAL) + 1

+ 50mV

RMS

RIPPLE

C

OUT

= 47µF

SOLID TANT

C

OUT

= 3.3µF

SOLID TANT

7

LT1529

LT1529-3.3/LT1529-5

CCHARA TERIST

ICS

UW

ATYPICA

LPER

F

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OUTPUT (Pin 1): OUTPUT Pin. The OUTPUT pin supplies
power to the load. A minimum output capacitor of 3.3µF is
required to prevent oscillations. Larger values will be
required to optimize transient response for large load
current deltas. See the Applications Information section
for further information on output capacitance and reverse
output characteristics.

SENSE (Pin 2): SENSE Pin. For fixed voltage versions of
the LT1529 (LT1529-3.3, LT1529-5) the SENSE pin is the
input to the error amplifier. Optimum regulation will be
obtained at the point where the SENSE pin is connected to
the output pin. For most applications the SENSE pin is
connected directly to the OUTPUT pin at the regulator. In
critical applications small voltage drops caused by the
resistance (RP) of PC traces between the regulator and the
load, which would normally degrade regulation, may be
eliminated by connecting the SENSE pin to the OUTPUT
pin at the load as shown in Figure 1 (Kelvin Sense Connec­tion). Note that the voltage drop across the external PC
traces will add to the dropout voltage of the regulator. The
SENSE pin bias current is 15µA at the nominal regulated
output voltage. This pin is internally clamped to –0.6V
(one VBE).

ADJ (Pin 2): Adjust Pin. For the LT1529 (adjustable
version) the ADJ pin is the input to the error amplifier. This

+

V

IN

V

IN

1

2

3

LT1529 • F01

5

4

OUTPUT

SENSE

LT1529-5

R

P

SHDN

GND

LOAD

+

R

P

Figure 1. Kelvin Sense Connection

pin is internally clamped to 6V and –0.6V (one VBE). This
pin has a bias current of 150nA which flows into the pin.
See Bias Current curve in the Typical Performance Char­acteristics. The ADJ pin reference voltage is equal to 3.75V
referenced to ground.

SHDN (Pin 4): Shutdown Pin. This pin is used to put the
device into shutdown. In shutdown the output of the
device is turned off. This pin is active low. The device will
be shut down if the SHDN pin is actively pulled low. The
SHDN pin current with the pin pulled to ground will be 6µA.
The SHDN pin is internally clamped to 7V and –0.6V (one
VBE). This allows the SHDN pin to be driven directly by 5V
logic or by open-collector logic with a pull-up resistor. The
pull-up resistor is only required to supply the leakage
current of the open-collector gate, normally several mi­croamperes. Pull-up current must be limited to a maxi­mum of 5mA. A curve of SHDN pin input current as a

Load Regulation

TEMPERATURE (°C)

–50

LOAD REGULATION (mV)

–5

0

5

25 75

LT1529 • G28

–10

–15

–25 0

50 100 125

–20

–25

LT1529-5

LT1529-3.3

LT1529

VIN = V

OUT

(NOMINAL) + 1V

∆I

LOAD

= 100mA to 3A

V

ADJ

= V

OUT

TIME (µs)

0

OUTPUT VOLTAGE

DEVIATION (V)

LOAD CURRENT (A)

–0.1

0.1

160

LT1529 • G30

2

–0.2

0

0.2

3

1

40

80

120

20 180

60

100

140

200

VIN = 6V
C

IN

= 10µF TANT

C

OUT

= 4.7µF TANT

LT1529-5 Transient Response

TIME (µs)

0

OUTPUT VOLTAGE

DEVIATION (V)

LOAD CURRENT (A)

–0.1

0.1

800

LT1529 • G29

2

–0.2

0

0.2

3

1

200

400

600

100 900

300

500

700

1000

VIN = 6V
C

IN

= 3.3µF TANT

C

OUT

= 47µF TANT

LT1529-5 Transient Response

8

LT1529
LT1529-3.3/LT1529-5

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function of voltage appears in the Typical Performance
Characteristics. If the SHDN pin is not used it can be left
open circuit. The device will be active, output on, if the
SHDN pin is not connected.

VIN (Pin 5): Input Pin. Power is supplied to the device
through the VIN pin. The VIN pin should be bypassed to
ground 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

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The LT1529 is a 3A low dropout regulator with mi­cropower quiescent current and shutdown capable of
supplying 3A of output current at a dropout voltage of

0.6V. The device operates with very low quiescent current
(50µA). In shutdown the quiescent current drops to only
16µA. In addition to the low quiescent current the LT1529
incorporates several protection features which make it
ideal for use in battery-powered systems. The device is
protected against reverse input voltages. In battery backup
applications where the output can be held up by a backup
battery when the input is pulled to ground, the LT1529 acts
like it has a diode in series with its output and prevents
reverse current flow.

Adjustable Operation

The adjustable version of the LT1529 has an output
voltage range of 3.75V to 14V. The output voltage is set
by the ratio of two external resistors as shown in Figure 2.
The device servos the output voltage to maintain the
voltage at the ADJ pin at 3.75V. The current in R1 is then
equal to 3.75V/R1. The current in R2 is equal to the sum
of the current in R1 and the ADJ pin bias current. The ADJ
pin bias current, 150nA at 25°C, flows through R2 into the
ADJ pin. The output voltage can be calculated according
to the formula in Figure 2. The value of R1 should be less
than 400k 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

include a bypass capacitor in battery-powered circuits. A
bypass capacitor in the range of 1µF to 10µF is sufficient.
The LT1529 is designed to withstand reverse voltages on
the VIN pin with respect to ground and OUTPUT pin. In the
case of a reversed input, which can happen if a battery is
plugged in backwards, the LT1529 will act as if there is a
diode in series with its input. There will be no reverse
current flow into the LT1529 and no reverse voltage will
appear at the load. The device will protect both itself and
the load.

+

V

IN

V

OUT

= 3.75V + (I

ADJ

× R2)

V

IN

V

OUT

R2

R1

1

2

3

LT1529 • F02

5

4

OUTPUT

SENSE

LT1529

SHDN

GND

()

1 +

R2
R1

V

ADJ

= 3.75V

I

ADJ

= 150nA AT 25°C

OUTPUT RANGE = 3.3V TO 14V

Figure 2. Adjustable Operation

Bias Current vs Temperature appear in the Typical Perfor­mance Characteristics. The reference voltage at the ADJ
pin has a positive temperature coefficient of approxi­mately 15ppm/°C. The ADJ pin bias current has a negative
temperature coefficient. These effects will tend to cancel
each other.

The adjustable device is specified with the ADJ pin tied to
the OUTPUT pin. This sets the output voltage to 3.75V.
Specifications for output voltage greater than 3.75V will be
proportional to the ratio of the desired output voltage to

3.75V (V

OUT

/3.75V). For example: load regulation for an
output current change of 1mA to 3A is –0.5mV typical at
V

OUT

= 3.75V. At V

OUT

= 12V, load regulation would be:

12

375

05 16

V

V

mV mV

.

–. –.











()

=

()

9

LT1529

LT1529-3.3/LT1529-5

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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. Ground pin current multiplied by the input voltage:
I

GND

• VIN .

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

The LT1529 series regulators have internal thermal limit­ing designed to protect the device during overload condi­tions. For continuous normal load 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. Experiments have shown that the
heat spreading copper layer does not need to be electri­cally connected to the tab of the device. The PC material
can be very effective at transmitting heat between the pad
area, attached to the tab of the device, and a ground or
power plane layer either inside or on the opposite side of
the board. Although the actual thermal resistance of the PC
material is high, the length/area ratio of the thermal
resistor between layers is small. Copper board stiffeners
and plated through-holes can also be used to spread the
heat generated by power devices.

The following tables list thermal resistances for each
package. For the TO-220 package, thermal resistance is
given for junction-to-case only since this package is
usually mounted to a heat sink. Measured values of
thermal resistance for several different copper areas are
listed for the DD package. All measurements were taken in
still air on 3/32" FR-4 board with 1-oz copper. This data can
be used as a rough guideline in estimating thermal resis-

tance. The thermal resistance for each application will be
affected by thermal interactions with other components as
well as board size and shape. Some experimentation will
be necessary to determine the actual value.

Table 1. Q Package, 5-Lead DD

COPPER AREA

TOPSIDE* BACKSIDE BOARD AREA

2500 sq. mm 2500 sq. mm 2500 sq. mm 23°C/W
1000 sq. mm 2500 sq. mm 2500 sq. mm 25°C/W
125 sq. mm 2500 sq. mm 2500 sq. mm 33°C/W
* Device is mounted on topside.

THERMAL RESISTANCE

(JUNCTION-TO-AMBIENT)

Calculating Junction Temperature

Example: Given an output voltage of 3.3V, an input voltage
range of 4.5V to 5.5V, an output current range of 0mA to
500mA, 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)

• (V

IN(MAX)

– V

OUT

) + (I

GND

• V

IN(MAX)

)

where, I

OUT(MAX)

= 500mA

V

IN(MAX)

= 5.5V

I

GND

at (I

OUT

= 500mA, VIN = 5.5V) = 3.6mA

so, P = 500mA • (5.5V – 3.3V) + (3.6mA • 5.5V)

= 1.12W

If we use a DD package, then the thermal resistance will be
in the range of 23°C/W to 33°C/W depending on copper
area. So the junction temperature rise above ambient will
be approximately equal to:

1.12W • 28°C/W = 31.4°C

The maximum junction temperature will then be equal to
the maximum junction temperature rise above ambient
plus the maximum ambient temperature or:

T

JMAX

= 50°C + 31.4°C = 81.4°C

Output Capacitance and Transient Performance

The LT1529 is designed to be stable with a wide range of
output capacitors. The minimum recommended value is

3.3µF with an ESR of 2Ω or less. The LT1529 is a

T Package, 5-Lead TO-220

Thermal Resistance (Junction-to-Case) = 2.5°C/W

10

LT1529
LT1529-3.3/LT1529-5

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micropower device and output transient response will be
a function of output capacitance. See the Transient Re­sponse curves in the Typical Performance Characteristics.
Larger values of output capacitance will decrease the peak
deviations and provide improved output transient re­sponse for larter load current deltas. Bypass capacitors,
used to decouple individual components powered by the
LT1529, will increase the effective value of the output
capacitor.

Protection Features

The LT1529 incorporates several protection features which
make it 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 device is protected against reverse input
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
15V. 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
that can be plugged in backwards.

For fixed voltage versions of the device, the SENSE pin is
internally clamped to one diode drop below ground. For
the adjustable version of the device, the OUTPUT pin is
internally clamped at one diode drop below ground. If the

OUTPUT pin of an adjustable device, or the SENSE pin of
a fixed voltage device, is pulled below ground, with the
input open or grounded, current must be limited to less
than 5mA.

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 flow back into the output will vary
depending on the conditions. Many battery-powered cir­cuits incorporate some form of power management. The
following information will help optimize battery life. Table
2 summarizes the following information.

The reverse output current will follow the curve in Figure
3 when the input is pulled to ground. This current flows
through the device to ground. The state of the SHDN pin
will have no effect on output current when the VIN pin is
pulled to ground.

Table 2. Fault Conditions

VIN PIN SHDN PIN OUTPUT/SENSE PINS

<V

OUT

(Nominal) Open (High) Forced to V

OUT

(Nominal) Reverse Output Current ≈ 15µA (See Figure 3), Input Current ≈ 1µA (See Figure 4)

<V

OUT

(Nominal) Grounded Forced to V

OUT

(Nominal) Reverse Output Current ≈ 15µA (See Figure 3), Input Current ≈ 1µA (See Figure 4)
Open Open (High) > 1V Reverse Output Current ≈ 15µA Peak (See Figure 3)
Open Grounded > 1V Reverse Output Current ≈ 15µA (See Figure 3)

≤0.8V Open (High) ≤0V Output Current = 0
≤0.8V Grounded ≤0V Output Current = 0

>1.5V Open (High) ≤0V Output Current = Short-Circuit Current

–15V < VIN < 15V Grounded ≤0V Output Current = 0

OUTPUT VOLTAGE (V)

0

OUTPUT CURRENT (µA)

60

80

100

8

LT1529 • F03

40

20

50

70

90

30

10

0

2

4

6

19

3

5

7

10

LT1529

LT1529-5

LT1529-3.3

TJ = 25°C, VIN = 0V
V

OUT

= V

SENSE

(LT1529-3.3/LT1529-5)
V

OUT

= V

ADJ

(LT1529)
CURRENT FLOWS
INTO DEVICE

Figure 3. Reverse Output Current

11

LT1529

LT1529-3.3/LT1529-5

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In some applications it may be necessary to leave the input
to the LT1529 unconnected when the output is held high.
This can happen when the LT1529 is powered from a
rectified AC source. If the AC source is removed, then the
input of the LT1529 is effectively left floating. The reverse
output current also follows the curve in Figure 3 if the V

IN

pin is left open. The state of the SHDN pin will have no
effect on the reverse output current when the VIN pin is
floating.

When the input of the LT1529 is forced to a voltage below
its nominal output voltage and its output is held high, the
output current will follow the curve shown in Figure 3 . This
can happen if the input of the LT1529 is connected to a
discharged (low voltage) battery and the output is held up
by either a backup battery or by a second regulator circuit.
When the VIN pin is forced below the OUTPUT pin or the
OUTPUT pin is pulled above the VIN pin, the input current

will typically drop to less than 2µA (see Figure 4). The state
of the SHDN pin will have no effect on the reverse output
current when the output is pulled above the input.

INPUT VOLTAGE (V)

0

INPUT CURRENT (µA)

3

4

5

4

LT1529 • F04

2

1

0

1

2

3

5

LT1529-5LT1529-3.3

V

OUT

= 3.3V (LT1529-3.3)

V

OUT

= 5V (LT1529-5)

Figure 4. Input Current

PACKAGE DESCRIPTIO

U

Dimensions in inches (millimeters) unless otherwise noted.

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 circuits as described herein will not infringe on existing patent rights.

Q Package

5-Lead Plastic DD Pak

(LTC DWG # 05-08-1461)

Q(DD5) 0396

0.028 – 0.038

(0.711 – 0.965)

0.143

+0.012
–0.020

()

3.632

+0.305
–0.508

0.057 – 0.077

(1.447 – 1.955)

0.013 – 0.023

(0.330 – 0.584)

0.095 – 0.115

(2.413 – 2.921)

0.004

+0.008
–0.004

()

0.102

+0.203
–0.102

0.050

± 0.012

(1.270 ± 0.305)

0.059

(1.499)

TYP

0.045 – 0.055

(1.143 – 1.397)

0.165 – 0.180

(4.191 – 4.572)

0.330 – 0.370

(8.382 – 9.398)

0.060

(1.524)

TYP

0.390 – 0.415

(9.906 – 10.541)

15

° TYP

0.300

(7.620)

0.075

(1.905)

0.183

(4.648)

0.060

(1.524)

0.060

(1.524)

0.256

(6.502)

BOTTOM VIEW OF DD PAK

HATCHED AREA IS SOLDER PLATED

COPPER HEAT SINK

12

LT1529
LT1529-3.3/LT1529-5

 LINEAR TECHNOLOGY CORPORATION 1995

152935fa LT/TP 0499 2K REV A • PRINTED IN USA

PACKAGE DESCRIPTIO

U

Dimensions in inches (millimeters) unless otherwise noted.

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T Package

5-Lead Plastic TO-220 (Standard)

(LTC DWG # 05-08-1421)

Linear Technology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

[phone] ● FAX: [phone]

●

www.linear-tech.com

T5 (TO-220) 0398

0.028 – 0.038

(0.711 – 0.965)

0.057 – 0.077

(1.448 – 1.956)

0.135 – 0.165

(3.429 – 4.191)

0.700 – 0.728

(17.78 – 18.491)

0.045 – 0.055

(1.143 – 1.397)

0.095 – 0.115

(2.413 – 2.921)

0.013 – 0.023

(0.330 – 0.584)

0.620

(15.75)

TYP

0.155 – 0.195

(3.937 – 4.953)

0.152 – 0.202

(3.861 – 5.131)

0.260 – 0.320
(6.60 – 8.13)

0.165 – 0.180

(4.191 – 4.572)

0.147 – 0.155

(3.734 – 3.937)

DIA

0.390 – 0.415

(9.906 – 10.541)

0.330 – 0.370

(8.382 – 9.398)

0.460 – 0.500

(11.684 – 12.700)

0.570 – 0.620

(14.478 – 15.748)

0.230 – 0.270

(5.842 – 6.858)