LT1033.pdf

LT1033

NOT RECOMMENDED FOR NEW DESIGNS

Contact Linear Technology for Potential Replacement

3A Negative Adjustable

Regulator

FEATURES

DESCRIPTIO

Guaranteed 1% Initial Voltage Tolerance

The LT ® 1033 negative adjustable regulator will deliver up

to 3A output current over an output voltage range of –1.2V

to –32V. Linear Technology has made significant

improvements in these regulators compared to previous

devices, such as better line and load regulation, and a

maximum output voltage error of 1%.

The LT1033 is easy to use and difficult to damage. Internal

current and power limiting as well as true thermal limiting

prevents device damage due to overloads or shorts, even

if the regulator is not fastened to a heat sink.

Maximum reliability is attained with Linear Technology’s

advanced processing techniques combined with a 100%

burn-in in the thermal limit mode. This assures that all

device protection circuits are working and eliminates field

failures experienced with other regulators that receive

only standard electrical testing.

Guaranteed 0.015%/ V Line Regulation

Guaranteed 0.02%/ W Thermal Regulation

PRECO DITIO I G

100% Thermal Limit Burn-in

APPLICATIO U

Adjustable Power Supplies

System Power Supplies

Precision Voltage/Current Regulators

On-Card Regulators

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

TYPICAL APPLICATIO

Negative 5V Regulator

Current Limit

301

TANT

100

ADJ

–V IN

OUT

–5V, 3A

LT1033

LT1033 • TA01

INPUT-OUTPUT DIFFERENTIAL (V)

LT1033 • G01

1033fc

LT1033

ABSOLUTE AXI U RATI GS

(Note 1)

Power Dissipation ....................................... Internally Limited

Input to Output Voltage Differential ................................. 35V

Operating Junction Temperature Range

LT1033M (OBSOLETE) ............................... –55

Storage Temperature Range

LT1033M (OBSOLETE) ............................... –65

C to 150

LT1033C ..................................................... –65

C to 150

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

LT1033C ......................................................... 0

C to 125

PACKAGE/ORDER I FOR ATIO

BOTTOM VIEW

FRONT VIEW

ADJ V OUT

V OUT

V IN

CASE IS

V IN

ADJ

CASE IS V IN

K PACKAGE

4-LEAD TO-3 METAL CAN

T JMAX = 150 ° C, q JA = 35 ° C/W(MK)

T JMAX = 125 ° C, q JA = 35 ° C/W(CK)

T PACKAGE

3-LEAD PLASTIC TO-220

T JMAX = 125

q JA = 50

C/W

P PACKAGE

3-LEAD PLASTIC TO-3P

T JMAX = 125

q JA = 35

C/W

OBSOLETE PACKAGE

Consider the P or T Packages for Alternate Source

ORDER PART NUMBER

LT1033CP

LT1033MK

LT1033CK

LT1033CT

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

ELECTRICAL CHARACTERISTICS

(Note 2)

The l denotes specifications which apply over the full operating temperature range, otherwise specifications are T A = 25

LT1033M

LT1033C

SYMBOL PARAMETER

CONDITIONS

MIN

TYP

MAX

MIN

TYP

MAX UNITS

V REF

Reference Voltage

|V IN – V OUT | = 5V, I OUT = 5mA,

T J = 25

–1.238 –1.250 –1.262 –1.238 –1.250 –1.262

3V £ |V IN – V OUT | £ 35V

5mA £ I OUT £ ˚ I MAX , P £ P MAX

–1.215 –1.250 –1.285 –1.200 –1.250 –1.300

D V OUT

Load Regulation

10mA £ I OUT £ I MAX , (Note 3)

D I OUT

T J = 25 ° C, |V OUT | £ 5V

T J = 25 ° C, |V OUT | ³ 5V

0.2

1.0

0.2

1.0

|V OUT | £ 5V

|V OUT | ³ 5V

0.4

1.5

0.4

1.5

V OUT

Line Regulation

|V IN – V OUT |

35V, (Note 2)

V IN

T J = 25

0.005

0.015

0.01

0.02

%/V

0.01

0.04

0.02

0.05

%/V

Ripple Rejection

V OUT = –10V, f = 120Hz

C ADJ = 0

C ADJ = 10 m F

Thermal Regulation

T J = 25 ° C, 10ms Pulse

0.002

0.02

0.002

0.02

%/W

1033fc

LT1033

ELECTRICAL CHARACTERISTICS

(Note 2)

The l denotes specifications which apply over the full operating temperature range, otherwise specifications are T A = 25

LT1033M

LT1033C

SYMBOL PARAMETER

CONDITIONS

MIN

TYP

MAX

MIN

TYP

MAX UNITS

I ADJ

Adjust Pin Current

100

m A

I ADJ

Adjust Pin Current Change 10mA

˚ I OUT

I MAX

0.2

0.5

3V £ |V IN – V OUT | £ 35V

1.0

m A

Minimum Load Current

|V IN – V OUT |

35V

2.5

5.0

2.5

5.0

|V IN – V OUT |

10V

1.2

3.0

1.2

3.0

I SC

Current Limit

|V IN – V OUT | £ 10V, (Note 3)

4.3

|V IN – V OUT | = 35V, T J = 25 ° C

0.5

1.3

2.5

0.5

1.3

2.5

V OUT

Temperature Stability of

T MIN

T MAX

0.6

1.5

0.6

1.5

Temp

Output Voltage

V OUT

Long Term Stability

T A = 125

C, 1000 Hours

0.3

1.0

0.3

1.0

Time

e n

RMS Output Noise

T A = 25 ° C, 10Hz £ f £ 10kHz

0.003

(% of V OUT )

q JC

Thermal Resistance

T Package

2.5

4.0

C/W

Junction to Case

K Package

1.2

2.0

1.2

2.0

C/W

P Package

1.8

2.7

C/W

Note 1: Absolute Maximum Ratings are those values beyond which the life

of a device may be impaired.

Note 2: Unless otherwise indicated, these specifications apply:

|V IN – V OUT | = 5V; and I OUT = 5mA. Power dissipation is internally limited.

However, these specifications apply for power dissipation up to 30W.

See guaranteed minimum output current curve. I MAX = 3A.

Note 3: Testing is done using a pulsed low duty cycle technique. See

thermal regulation specifications for output changes due to heating effects.

Load regulation is measured on the output pin at a point 1/8" below the

base of the package.

TYPICAL PERFOR A CE CHARACTERISTICS

Dropout Voltage

Temperature Stability

Minimum Load Current

2.8

1.27

1.8

2.6

1.6

T J = –55

1.4

1.26

2.4

2.2

1.2

T J = 25

1.0

2.0

1.25

T J = 25

T J = 150

0.8

1.8

0.6

T J = 150 ° C

1.6

1.24

0.4

1.4

0.2

1.2

1.23

0.5

1.0

1.5

2.0

2.5

3.0

–75

–50

–25

75 100 125 150

OUTPUT CURRENT (A)

TEMPERATURE ( ° C)

INPUT-OUTPUT DIFFERENTIAL (V)

LT1033 • G02

LT1033 • G03

LT1033 • G04

1033fc

LT1033

TYPICAL PERFOR M A N CE CHARACTERISTICS

Ripple Rejection

100

C ADJ = 10

C ADJ = 10 µ F

C ADJ = 0

C ADJ = 10 µ F

C ADJ = 0

V IN – V OUT = 5V

I L = 500mA

f = 120Hz

T J = 25

V IN = –15V

V OUT = –10V

I L = 500mA

T J = 25

V IN = –15V

V OUT = –10V

f = 120Hz

T J = 25

–10

–20

–30

–40

100

10k

100k

0.01

0.1

OUTPUT VOLTAGE (V)

FREQUENCY (Hz)

OUTPUT CURRENT (A)

LT1033 • G05

LT1033 • G06

LT1033 • G07

Output Impedance

Line Transient Response

Load Transient Response

10 1

0.8

0.6

V IN = –15V

V OUT = –10V

I L = 500mA

C L = 1

0.6

0.4

C ADJ = 0

0.4

0.2

10 0

C ADJ = 0

T J = 25

0.2

C ADJ = 10

–0.2

10 –1

C ADJ = 10

–0.4

C ADJ = 0

–0.2

–0.6

–0.4

V IN = –15V

V OUT = –10V

I NL = 50mA

T J = 25

10 –2

C ADJ = 10

V OUT = –10V

I L = 50mA

T J = 25 ° C

C L = 1 µ F

–0.5

–1.0

C L = 1

–1.0

10 –3

–1.5

100

10k

100k

FREQUENCY (Hz)

TIME (

LT1033 • G08

LT1033 • G09

LT1033 • G10

Load Regulation*

Guaranteed Minimum

Output Current

Adjustment Current

0.8

0.4

–0.4

–0.8

0.8

1.6

2.4

3.2

4.0

–75 –50 –25 0 25

50 75 100 125

150

OUTPUT CURRENT (A)

INPUT-OUTPUT DIFFERENTIAL (V)

TEMPERATURE (

*THE LT1033 HAS LOAD REGULATION COMPENSATION

WHICH MAKES THE TYPICAL UNIT READ CLOSE TO ZERO.

THIS BAND REPRESENTS THE TYPICAL PRODUCTION SPREAD

LT1033 • G12

LT1033 • G13

LT1033 • G11

1033fc

LT1033

APPLICATIO N S I N FOR M ATIO N

Output Voltage

The output voltage is determined by two external resis-

tors, R1 and R2 (see Figure 1). The exact formula for the

output voltage is:

which must be absorbed, is 5mA for the LT1033. If input-

output voltage differential is less than 10V, the operating

current that must be absorbed drops to 3mA.

Capacitors and Protection Diodes

An output capacitor, C3, is required to provide proper

frequency compensation of the regulator feedback loop.

A 2

OUT

REF

÷ +

ADJ

()

F or larger solid tantalum capacitor is generally

sufficient for this purpose if the 1MHz impedance of the

capacitor is 1

Where: V REF = Reference Voltage, I ADJ = Adjustment Pin

Current. In most applications, the second term is small

enough to be ignored, typically about 0.5% of V OUT . In

more critical applications, the exact formula should be

used, with I ADJ equal to 65

or less. High Q capacitors, such as Mylar,

are not recommended because their extremely low ESR

(effective series resistance) can drastically reduce phase

margin. When these types of capacitors must be used

because of other considerations, add a 0.5

A. Solving for R2 yields:

OUT

–

REF

carbon

F. Aluminum electrolytic capaci-

tors may be used, but the minimum value should be 25

REF

–

ADJ

to ensure a low impedance at 1MHz. The output capacitor

should be located within a few inches of the regulator to

keep lead impedance to a minimum. The following caution

should be noted: if the output voltage is greater than 6V

and an output capacitor greater than 20

, giving 12.5mA and 4.2mA

no-load current respectively. There is an additional con-

sideration in selecting R1, the minimum load current

specification of the regulator. The operating current of the

LT1033 flows from input to output. If this current is not

absorbed by the load, the output of the regulator will rise

above the regulated value. The current drawn by R1 and R2

is normally high enough to absorb the current, but care

must be taken in no-load situations where R1 and R2 have

high values. The maximum value for the operating current,

and 300

F has been used,

it is possible to damage the regulator if the input voltage

becomes shorted, due to the output capacitor discharging

into the regulator. This can be prevented by using diode D1

(see Figure 2) between the input and the output.

The input capacitor, C2, is only required if the regulator is

more than 4 inches from the raw supply filter capacitor.

Bypassing the Adjustment Pin

The adjustment pin of the LT1033 may be bypassed with

a capacitor to ground, C1, to reduce output ripple, noise,

and impedance. These parameters scale directly with

output voltage if the adjustment pin is not bypassed. A

bypass capacitor reduces ripple, noise and impedance to

that of a 1.25V regulator. In a 15V regulator for example,

these parameters are improved by 15V/1.25V = 12 to 1.

This improvement holds only for those frequencies where

the impedance of the bypass capacitor is less than R1. Ten

microfarads is generally sufficient for 60Hz power line

applications where the ripple frequency is 120Hz, since

X C = 130

10 µ F

I ADJ

V REF

ADJ

–V IN

V IN

V OUT

–V OUT

LT1033

LT1033 • F01

EXAMPLE:

1. A PRECISION 10V REGULATOR TO SUPPLY UP TO 3A LOAD CURRENT.

A. SELECT R1 = 100 ½ TO MINIMIZE EFFECT OF I ADJ

B. CALCULATE R2 =

V OUT – V REF

V REF

10V – 1.25V

1.25V

100 ½

= 704 ½

. The capacitor should have a voltage rating at

least as high as the output voltage of the regulator. Values

– I ADJ

– 65

Figure 1

1033fc

resistor in series with 1

Smaller values of R1 and R2 will reduce the influence of

I ADJ on the output voltage, but the no-load current drain on

the regulator will be increased. Typical values for R1 are

between 100

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