LP2950CT-3.0 - Sipex Corporation

Rev. 11/2/00

LP2950/LP2951

100 mA Low Dropout Voltage Regulators

FEATURES APPLICATIONS

• 5.0V, 3.3V and 3.0V Versions @ 100mA Output • Battery Powered Systems

• Very Low Quiescent Current • Cordless Telephones

• Low Dropout Voltage • Radio Control Systems

• Extremely Tight Load and Line Regulation • Portable/Palm Top/Notebook Computers

• Very Low Temperature Coefficient • Portable Consumer Equipment

• Current & Thermal Limiting • Portable Instrumentation

• Need Only 1 µF for Stability • Avionics

• Offered in TO-263 & SOIC • SMPS Post-Regulator

• Direct Replacement For LP2950/LP2951 Sockets • Voltage Reference

• Automotive Electronics

LP2951 versions only

• Error Flag Warns of Output Dropout

• Logic-Controlled Electronic Shutdown

• Output Programmable From 1.24 to 29V

PRODUCT DESCRIPTION

The LP2950 and LP2951 are low power voltage regulators. These devices are an excellent choice for use in battery-powered

applications such as cordless telephones, radio control systems, and portable computers. The LP2950 and LP2951 features low

quiescent current and very low dropout voltage (Typ. 50mV at light load and 380 mV at 100mA). This includes a tight initial

tolerance of 0.5% typ., extremely good load and line regulation 0.05% typ., and very low output temperature coefficient, making the

LP2950/LP2951 useful as a low-power voltage reference.

The error flag output feature is used as power-on reset for warning of a low output voltage, due to falling voltage input of batteries.

Another feature is the logic-compatible shutdown input which enables the regulator to be switched ON and OFF. The LP2950 is

offered in a 3-pin TO-263 package compatible with other 5V, 3.0V & 3.3V regulators. The LP2951 is also available in 8-pin plastic,

SO-8 packages.

The regulator output voltage may be pin-strapped for 5.0V, 3.0V or 3.3V or programmed from 1.24V to 29V with an external pair of

resistors. Look for SPX2950/51 for 150mA, for SPX2975 for 180mA and SPX2954 for 250mA.

8-Pin Surface Mount (S)

ALPHA

AS2930

1

Top View

2

3

45

6

7

8

LP2951

OUTPUT

SENSE

SHUTDOWN

GROUND

INPUT

FEEDBACK

5V or 3.3V TAP

ERROR

Top View

TO-263-3 (T)

1

LP2950

23

V

IN

V

OUT

GND

Rev. 11/2/00

LP2950/51

ABSOLUTE MAXIMUM RATINGS

Power Dissipation ..................................Internally Limited Input Supply Voltage ................................................ -0.3V to +30V

Lead Temp. (Soldering, 5 Seconds) ......................... 260°C Feedback Input Voltage ............................................ -1.5V to +30V

Storage Temperature Range .......................-65° to +150°C Shutdown Input Voltage............................................ -0.3V to +30V

Operating Junction Temperature Range Error Comparator Output .......................................... -0.3V to +30V

LP2951 ........................................... -55°C to +150°C ESD Rating ...................................................................... 2kV Min

LP2950AC/LP2950C...................... -40°C to +125°C

LP2951AC/LP2951C...................... -40°C to +125°C

ELECTRICAL CHARACTERISTICS at Vs=15V, Ta=25°C, unless otherwise noted.

PARAMETER

CONDITIONS

(Note 2)

LP2951

Min. Typ. Max.

LP2950AC

LP2951AC

Min. Typ. Max.

LP2950C

LP2951C

Min. Typ. Max.

UNITS

3 V Versions

Output Voltage TJ = 25°C

-25°C ≤TJ ≤85°C

Full Operating Temperature

2.985

2.964

3.0 3.015

3.036

2.985

2.970

2.964

3.0

3.015

3.030

3.036

2.970

2.955

2.940

3.0

3.030

3.045

3.060

V

Output Voltage 100 µA ≤IL ≤100 mA

TJ ≤TJMAX

2.955 3.0 3.045 2.958 3.0 3.042 2.928 3.0 3.072 V

3.3 V Versions

Output Voltage TJ = 25°C

-25°C ≤TJ ≤85°C

Full Operating Temperature

3.284

3.260

3.3 3.317

3.340

3.284

3.267

3.260

3.3

3.317

3.333

3.340

3.267

3.251

3.234

3.3

3.333

3.350

3.366

V

Output Voltage 100 µA ≤IL ≤100 mA

TJ ≤TJMAX

3.251 3.3 3.350 3.254 3.3 3.346 3.221 3.3 3.379 V

5 V Versions

Output Voltage TJ = 25°C

-25°C ≤TJ ≤85°C

Full Operating Temperature

4.975

4.94

5.0 5.025

5.06

4.975

4.95

4.94

5.0

5.025

5.050

5.06

4.95

4.925

4.90

5.0

5.05

5.075

5.10

V

Output Voltage

100 µA ≤IL ≤100 mA

TJ ≤TJMAX

4.925 5.0 5.075 4.93 5.0 5.07 4.88 5.0 5.12 V

All Voltage Options

Output Voltage

Temperature Coefficient

(Note 1)

20 120 20 120 50 120 ppm/°C

Line Regulation (Note

3)

6V ≤Vin ≤30V (Note 4) 0.03 0.1 0.03 0.1 0.04 0.2 %

Load Regulation (Note

3)

100 µA ≤IL ≤ 100 mA 0.04 0.1 0.04 0.1 0.1 0.2 %

Dropout Voltage

(Note 5)

IL = 100µ A

IL = 100 mA

50

380

80

450

50

380

80

450

50

380

80

450

mV

Ground Current

IL = 100 µA

IL = 100 mA

150

8

170

12

150

8

170

12

150

8

170

12

µA

mA

Current Limit VOUT = 0 130 200 130 200 130 200 mA

Thermal Regulation 0.05 0.2 0.05 0.2 0.05 0.2 %/W

Output Noise,

10Hz to 100KHz

CL = 1µF

CL = 200 µF

CL = 13.3 µF

(Bypass = 0.01 µF pins 7 to

1(LP2951))

430

160

100

430

160

100

430

160

100

µV rms

8-Pin Versions only LP2951 LP2951AC LP2951C

Reference Voltage 1.22 1.235 1.25 1.22 1.235 1.25 1.21 1.235 1.26 V

Reference Voltage Over Temperature (Note 6) 1.19 1.27 1.19 1.27 1.185 1.285 V

Feedback Pin Bias

Current

40 60 40 60 40 60 nA

Rev. 11/2/00

FEEDBACK IN PUT OUTPUT

UNREGULATED DC

SHUTDOWN

GROUND

ERROR

______

5V TAP

SENSE

5V @ 100mA

MAX

TO CMOS OR

TTL

REFERENCE

ERROR DETECTION

COMPARATOR

ERROR

AM PL IFIE R

1.23V

FROM

CMOS OR

TTL

+

60 mV

3

781

2

6

5

4

Ω ..

60k

330k

180k

Ω ..

µ ..1F

_

LP2950 and LP2951 Block Diagram

LP2950/51

PARAMETER

CONDITIONS

(Note 2)

LP2951

Min. Typ. Max.

LP2950AC

LP2951AC

Min. Typ. Max.

LP2950C

LP2951C

Min. Typ. Max.

UNITS

8-Pin Versions only (Continued)

Reference Voltage

Temperature

Coefficient

( Note 7 )

20 20 50 ppm/°C

Feedback Pin Bias

Current

Temperature Coefficient

0.1 0.1 0.1 nA/°C

Error Comparator

Output Leakage Current VOH = 30V 0.01 1 0.01 1 0.01 1 µA

Output Low Voltage VIN = 4.5V

IOL = 400µA

150 250 150 250 150 250 mV

Upper Threshold

Voltage

(Note 8) 40 60 40 60 40 60 mV

Lower Threshold

Voltage

(Note 8) 75 95 75 95 75 95 mV

Hysteresis (Note 8) 15 15 15 mV

Shutdown Input

Input logic Voltage Low (Regulator ON)

High (Regulator OFF)

2

1.3 0.6

2

1.3 0.7

2

1.3 0.7 V

V

Shut down Pin Input

Current

VS = 2.4V

VS= 30V

30

675

50

800

30

675

50

800

30

675

50

800

µA

Regulator Output

Current in Shutdown

(Note 9) 3 10 3 10 3 10 µA

Note 1: Output or reference voltage temperature coefficients defined as the worst case voltage change divided by the total temperature range.

Note 2: Unless otherwise specified all limits guaranteed for TJ = 25°C, VIN = 6V, IL = 100µA and CL = 1µF. Additional conditions for the 8-pin versions are feedback

tied to 5V tap and output tied to output sense (VOUT = 5V) and VSHUTDOWN ≤ 0.8V.

Note 3: Regulation is measured at constant junction temperature, using pulse testing with a low duty cycle. Changes in output voltage due to heating effects are

covered under the specification for thermal regulation.

Note 4: Line regulation for the LP2951 is tested at 150°C for IL = 1mA. For IL = 100 µA and TJ = 125°C, line regulation is guaranteed by design to 0.2%. See typical

performance characteristics for line regulation versus temperature and load current.

Note 5: Dropout voltage is defined as the input to output differential at which the output voltage drops 100 mV below its nominal value measured at 1V differential at

very low values of programmed output voltage, the minimum input supply voltage of 2V ( 2.3V over temperature) must be taken into account.

Note 6: VREF ≤VOUT ≤ (VIN - 1V), 2.3 ≤VIN≤30V, 100µA≤IL≤ 100 mA, TJ ≤ TJMAX.

Note 7: Comparator thresholds are expressed in terms of a voltage differential at the feedback terminal below the nominal reference voltage measured at 6V input. To

express these thresholds in terms of output voltage change, multiply by the error amplifier gain = VOUT/VREF = (R1 + R2)/R2. For example, at a programmed output

voltage of 5V, the error output is guaranteed to go low when the output drops by 95 mV x 5V/1.235 = 384 mV. Thresholds remain constant as a percent of VOUT as VOUT

is varied, with the dropout warning occurring at typically 5% below nominal, 7.5% guaranteed.

Note 8: VSHUTDOWN ≥ 2V, VIN ≤ 30V, VOUT =0, Feedback pin tied to 5V Tap.

Note 9: All typical values are not guaranteed. The value could vary from lot to lot.

BLOCK DIAGRAM

Rev. 11/2/00

LP2950/51

APPLICATION HINTS

EXTERNAL CAPACITORS

The stability of the LP2950/LP2951 requires a 1.0 µF or greater

capacitor between output and ground. Oscillation could occur without

this capacitor. Most types of tantalum or aluminum electrolytic

works fine here. For operations below -25°C solid tantalum is

recommended since the many aluminum types have electrolytes that

freeze at about -30°C. The ESR of about 5 Ω or less and resonant

frequency above 500 kHz are the most important parameters in the

value of the capacitor. The capacitors value may be increased

without limit.

At lower values of output current, less output capacitance is required

for stability. For the currents below 10 mA the value of the capacitor

can be reduced to 0.33 µF and 0.1 µF for 1 mA. More output

capacitance is needed for the 8-pin version at voltages below 5V

since it runs the error amplifier at lower gain. At worst case 3.3 µF or

greater must be used for the condition of 100 mA load at 1.23V

output.

The LP2950/51 unlike other low dropout regulators will remain

stable and in regulation with no load in addition to the internal

voltage divider. This feature is especially important in applications

like CMOS RAM keep-alive. When setting the output voltage of the

LP2950/51 version with external resistors, a minimum load of 1µA is

recommended

If there is more than 10 inches of wire between the input and the AC

filter capacitor or if a battery is used as the input then a 1µA tantalum

or aluminum electrolytic capacitor should be placed from the input to

the ground.

Instability can occur if there is stray capacitance to the LP2951

feedback terminal (pin 7). This could cause more problems when

using a higher value of external resistors to set the output voltage.

This problem can be fixed by adding a 100 pF capacitor between

output and feedback and increasing the output capacitor to at least 3.3

µF.

ERROR DETECTION COMPARATOR OUTPUT

The Comparator produces a logic low output whenever the LP2951

output falls out of regulation by more than around 5%. This is around

60 mV offset divided by the 1.235 reference voltage. This trip level

remains 5% below normal regardless of the programmed output

voltage of the regulator.

Figure 1 shows the timing diagram depicting the ERROR signal and

the regulator output voltage as the LP2951 input is ramped up and

down. The ERROR signal becomes low at around 1.3V input, and

goes high around 5V input (input voltage at which VOUT = 4.75 ).

Since the LP2951’s dropout voltage is load dependent, the input

voltage trip point (around 5V) will vary with the load current. The

output voltage trip point (approx. 4.75V) does not vary with load.

The error comparator has an open-collector output, which requires an

external pull-up resistor. Depending on the system requirements the

resistor may be returned to 5V output or other supply voltage. In

determining the value of this resistor, note that the output is rated to

sink 400µA, this value adds to battery drain in a low battery

condition. Suggested values range from 100K to 1MΩ. If the output

is unused this resistor is not required.

PROGRAMMING THE OUTPUT VOLTAGE OF LP2951

The LP2951 may be pin-strapped for 5V using its internal voltage

divider by tying Pin 1 (output) to Pin 2 (sense) and Pin 7 (feedback)

to Pin 6 (5V Tap). Also, it may be programmed for any output

voltage between its 1.235V reference and its 30V maximum rating .

As seen in Figure 2, an external pair of resistors is required. Refer to

the below equation for the programming of the output voltage:

VOUT = VREF × (1 + R1/R2)+ IFBR1

The VREF is 1.235 and IFB is the feedback bias current, nominally -20

nA. The minimum recommended load current of 1 µA forces an

upper limit of 1.2 MΩ on value of R2. If no load is presented the IFB

produces an error of typically 2% in VOUT which may be eliminated

at room temperature by trimming R1. To improve the accuracy

choose the value of R2 = 100k this reduces the error by 0.17% and

increases the resistor program current by 12 µA. Since the LP2951

typically draws 60 µA at no load with Pin 2 open-circuited this is a

small price to pay

REDUCING OUTPUT NOISE

It may be an advantage to reduce the AC noise present at the output.

One way is to reduce the regulator bandwidth by increasing the size

of the output capacitor. This is the only way that noise can be

reduced on the 3 lead LP2950 but is relatively inefficient, as

increasing the capacitor from 1 µF to 220 µF only decreases the noise

from 430 µV to 160 µVRMS for a 100 kHz bandwidth at 5V output.

Noise could also be reduced fourfold by a bypass capacitor across R1,

since it reduces the high frequency gain from 4 to unity. Pick

CBYPASS ≅ 1 / 2πR1 × 200 Hz

or choose 0.01 µF. When doing this, the output capacitor must be

increased to 3.3 µF to maintain stability. These changes reduce the

output noise from 430 µV to 100 µVRMS for a 100 kHz bandwidth at

5V output. With the bypass capacitor added, noise no longer scales

with output voltage so that improvements are more dramatic at higher

output voltages.

+

4.75V

OUTPUT

VOLTAGE

ERROR*

_______

INPUT

VOLTAGE 1.3V

5.0V

Figure 1. ERROR Output Timing

_______

* See Application Info.

Rev. 11/2/00

LP2950/ LP2951

TYPICAL PERFORMANCE CHARACTERISTIC

INPUT CURRENT (mA)

160

150

140

130

70

50

0

INPUT VOLTAGE (VOLTS)

GROUND PIN CURRENT (mA)

10

1

0.1

0.01

0.1 1 10 150

LOAD CURRENT (mA)

120

110

100

90

80

60

40

30

20

10

0

12345678910

INPUT CURRENT

QUIESCENT CURRENT

240

220

200

180

-75 -50 -25 0 25 50 75 100 125 150

TEMPERATURE (ºC)

QUIESCENT CURRENT

QUIESCENT CURRENT (µA)

170

150

130

110

-75 -50 -25 0 25 50 75 100 125 150

TEMPERATURE (ºC)

SHORT CIRCUIT CURRENT

SHORT CIRCUIT CURRENT (mA)

160

140

120

110

V

IN

=6V

I

L

=100mA

R

L

=50

Ω

600

400

300

50

-75 -50 -25 0 25 50 75 100 125 150

TEMPERATURE (ºC)

DROP-OUT VOLTAGE

DROP-OUT VOLTAGE (mV)

500

100

0

OUTPUT VOLTAGE (V)

5.06

5.04

5.0

TEMPERATURE (ºC)

OUTPUT VOLTAGE (VOLTS)

0

INPUT VOLTAGE (VOLTS)

5.02

4.98

4.96

4.94

OUTPUT VOLTAGE VS. TEMP OF 3

REPRESENTATIVE UNITS

DROPOUT CHARACTERISTICS

16

12

8

4

-75 -50 -25 0 25 50 75 100 125 150

TEMPERATURE (ºC)

GROUND CURRENT

GROUND CURRENT (mA)

123 456

1

2

3

4

5

6

-75 -50 -25 0 25 50 75 100 125 150

0.2%

I

L

= 100mA

I

L

= 100µA

R

L

=50k

Ω

R

L

=50k

Ω

V

IN

= 6V

I

L

= 100mA

~

INPUT CURRENT (µA)

75

0

010 150

INPUT VOLTAGE (VOLTS)

INPUT CURRENT

GROUND CURRENT (µA)

320

280

0

INPUT VOLTAGE (VOLTS)

240

80

40

012345678

GROUND CURRENT

16

14

12

012345678

INPUT VOLTAGE

GROUND CURRENT

R

L

= 50k

Ω

25

50

100

125

150

175

200

225

250

123

120

160

200

10

8

6

4

2

0

I

L

= 1mA

I

L

= 0

I

L

=100mA

T

J

= 25ºC

DROP-OUT VOLTAGE

OUTPUT CURRENT

DROP-OUT VOLTAGE (mV)

100mA

10mA

1mA100µA

500

400

300

200

100

0

R

L

=

8

Rev. 11/2/00

LP2950/LP2951

TYPICAL PERFORMANCE CHARACTERISTICS (continued)

10

0.5

0.1

0.02

10 100 1K 10K 100K 1M

FREQUENCY (Hz)

OUTPUT IMPEDANCE

OUTPUT IMPEDANCE (OHMS)

5

0.2

0.05

0.01

90

70

60

40

10

1

10

2

10

3

10

4

10

5

10

6

FREQUENCY (Hz)

RIPPLE REJECTION

RIPPLE REJECTION (dB)

80

50

20

RIPPLE REJECTION

FREQUENCY (Hz)

RIPPLE REJECTION (dB)

10

6

10

3

10

2

10

1

90

80

70

60

50

20

1

2

30

I

L

= 100µA

I

L

= 0

C

L

= 1µF

V

IN

= 6V

V

OUT

= 5V

40

30

10

4

10

5

I

L

= 10mA

I

L

= 10mA

C

L

= 1µF

V

IN

= 6V

V

OUT

= 5V

I

O

= 100mA

I

O

= 100µA

I

O

= 1mA

V

OUT

= 5V

C

L

= 1µF

COMPARATOR OUTPUT (V)

8

6

0

INPUT VOLTAGE (V)

4

2

0

-2

12345

ERROR COMPARATOR OUTPUT

SINK CURRENT (mA)

2.5

1.5

OUTPUT LOW VOLTAGE (V)

2.0

1.0

0.5

0.0

COMPARATOR SINK CURRENT

TIME(µs)

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

V

OUT

= 5V

PULLUP RESISTOR TO

SEPARATE 5V SUPPLY

HYSTERESIS

100

0 200 400 600 800

LINE TRANSIENT RESPONSE

INPUT OUTPUT VOLTAGE

VOLTAGE CHANGE

4V

6V

8V

-50

0

50

~

mV

C

L

= 1µF

I

L

= 1mA

V

OUT

= 5V

T

A

= -55ºC

T

A

= 25ºC

T

A

= 125ºC

LP2951

7

6

4

-100 0100 200 300 400 500 600 700

TIME

ENABLE TRANSIENT

SHUTDOWN OUTPUT

PINOUT VOLTAGE (V) VOLTAGE (V)

3

2

1

0

2

-2

250

100

-50

100

012345

TIME (ms)

LOAD TRANSIENT RESPONSE

LOAD OUTPUT VOLTAGE

CURRENT CHANGE (mV)

µA

~

mA

-100

0

50

150

200

C

L

= 1µF

V

OUT

= 5V

80

20

-40

100

04 8121620

TIME (ms)

LOAD TRANSIENT RESPONSE

LOAD OUTPUT VOLTAGE

CURRENT CHANGE (mV)

µA

100

-60

-20

0

40

60

µA

C

L

= 1µF

V

OUT

= 5V

0

5

C

L

= 10µF V

OUT

= 5V

V

IN

= 8V

I

L

= 10mA

100

~

MINIMUM OPERATING VOLTAGE (V)

10

1

0.1

0.01

-75 0 75 150

TEMPERATURE

MINIMUM OPERATING VOLTAGE

BIAS CURRENT (nA)

-30

-75

TEMPEATURE (ºC)

FEEDBACK BIAS CURRENT

FEEDBACK CURRENT (µA)

-150

-250

-2.0 -0.5 1.0

FEEDBACK VOLTAGE (V)

FEEDBACK PIN CURRENT

-50 0 50 75 100 150

-20

-10

0

10

20

-200

-100

-50

0

50

-1.5 -1.0

-50 -25 25 50 100 125 -25 25 125 0 0.5

T

A

= 25ºC

T

A

= 55ºC

T

A

=1 25ºC

LP2951 LP2951 LP2951

PIN 7 DRIVEN BY EXTERNAL

SOURCE (REGULATOR RUN

OPEN LOOP)

Rev. 11/2/00

LP2950/LP2951

TYPICAL PERFORMANCE CHARACTERISTICS (continued)

VOLTAGE NOISE

SPECTRAL DENSITY (µV/Hz)

3.5

2.5

2.0

0.0

10

2

10

3

10

4

10

5

FREQUENCY (Hz)

OUTPUT NOISE

I

L

= 100mA

C

L

= 1µF

C

L

= 220µF

C

L

= 3.3µF

3.0

1.5

1.0

0.5

OUTPUT CURRENT (mA)

120

100

60

40

0

INPUT VOLTAGE (V)

80

20

0

510 15 202530

LP2950 MAXIUM RATED OUTPUT

CURRENT

T

JMAX

= 125º C

V

OUT

= 5V

T

A

= 25ºC

T

A

= 50ºC

T

A

= 85ºC

8-PIN

MOLDED

DIP SOLDERED

TO PC BOARD

SHUTDOWN THRESHOLD VOLTAGE (V)

1.8

1.6

1.0

-75

TEMPERATURE (ºC)

1.4

1.2

0.8

0.6

-50 -25 0 25 50 75 100 125 150

SHUTDOWN THRESHOLD VOLTAGE

OUTPUT CURRENT (mA)

120

80

0

010 20 30

INPUT VOLTAGE (V)

LP2950 MAXIUM RATED OUTPUT

25155

T

A

= 85 ºC

T

A

=25 ºC

T

JMAX

= 125 ºC

0.25" LEADS SOLDERED

TO-92 PACKAGE

TO PC BOARD

100

60

40

20

RIPPLE REJECTION (dB)

80

60

40

10

1

10

3

10

4

10

6

FREQUENCY (Hz)

RIPPLE REJECTION

I

L

= 50µA

I

L

= 100mA

C

L

= 1µF

V

IN

= 6V

V

OUT

= 5V

70

50

30

20

10

2

10

5

OUTPUT VOLTAGE CHANGE (mV)

30

25

20

10

5

INPUT VOLTAGE (V)

15

10

5

0

5

0

-5

-10

10 15 20 25 30

LINE REGULATION

~

I

L

= 100µA

I

L

= 1mA

T

J

= 150 ºC

T

J

= 125 ºC I

L

= 100µA

PIN 2 TO PIN 4 RESISTANCE (k

Ω)

Ω)Ω)

Ω)

400

200

100

0

-75 0 75 150

TEMPERATURE (ºC)

LP2951 DIVIDER RESISTANCE

-50 -25 25 50 100 125

300

POWER OUTPUT VOLTAGE

DISSIPATION (W) CHANGE (mV)

4

2

1

0

TIME (µs)

0

-2

0

-1

10 20 30 40 50

THERMAL RESPONSE

5

1.25W

~

Rev. 11/2/00

LP2950/LP2951

TYPICAL APPLICATIONS

100K

OUTPUT

ERROR

______

SD

VOUT

GND FB

+VIN

1.23V

1.2 to30V

R1

.01uF

3.3uF

R2

VREF

3

8

5

1

47

SHUTDOWN

INPUT

+

Figure 1. Adjustable Regulator

LP2951

470K

ERROR

______

SD

V

OUT

GND

+V

IN

+V

IN

R

1 1uF

R

2

3

8

5

1

4

+

FB

7

V

OUT

Ω

..

Ω

..

470K

LP2951

Fig.2 Latch Off When Error Flag Occurs

OUTPUT

ERROR ERROR

______

SD

V

OUT

GND FB

+V

IN

+V

IN

*V

OUT

= V

IN

3

8

5

1

4 7

SHUTDOWN

INPUT

LP2951

Fig.3 Wide Input Voltage Range Current Limiter

*MINIMUM INPUT-OUTPUT VOLTAGE RANGES FROM 4mV TO 400mV.

DEPENDING ON LOAD CURRENT. CURRENT LIMIT IS TYPICALLY 160mA

Rev. 11/2/00

LP2950/LP2951

TYPICAL APPLICATIONS (continued)

100K

SENSE

SD

V

OUT

GND

+V

IN

3

8

1

1uF

+

4

Ω

..

Ω

..

400K

120K 1.5K

Ω

..

Ω

..

6V

SEALED

LEAD-

ACID

BATTERY

SOURCE FB

FOR 5.5 V

+

1N457

2 Ω

..

20K

NI-CAD

BACKUP

BATTERY

MEMORY V+

MAIN V-

AS385

Fig.4 Low Battery Disconnect

LP2951

GND

4

3

5

8 2

1

7

6

SD

TAP

FB

+V

IN SENSE

V

OUT

ERROR

______

RESET

100k

1k

100k

10k

20k

1k

39k

C3

C1

C2

C4

1%

6V

LEAD-

ACID

BATTERY

R

3

<6.2V**

<5.8V**

<6.0V**

-

+

-

Ω

..

Ω

..

Ω

..

Ω

..

Ω

..

Ω

..

Ω

..

Ω

..

Ω

..

Ω

..

+V

OUT

= 5V

1uF

+

Fig. 5 Regulator with State-of-Charge Indicator

* OPTIONAL LATCH OFF WHEN DROPOUT OCCURS. ADJUST R3 FOR C2 SWITCHING WHEN

V

IN

IS 6.0V

* OUTPUTS GO LOW WHEN V IN

DROPS BELOW DESGNATED THRESHHOLDS

LP2951

Rev. 11/2/00

LP2950/LP2951

TYPICAL APPLICATIONS (continued)

330K

IN

V

OUT

FB

3

5

1

4.7uF

+

7

Ω

..

Ω

..

27K

LP2951

V

TAP GND

SENSE

4

2

UNREGULATED INPUT

2N5432

5V

OUTPUT

LOAD

50mA

TO

300 mA

Fig 8. 300 mA Regulator with 0.75V

360K

0.1uF

V

OUT

MIN VOLTAGE = 4V

+V

IN

8

1

FB 7

1N4001

20mA

1N457

4.7mA

+5V

OUTPUT

2

GND

4

Open Circuit Detector for 4mA to 20mA Current Loop

LP2951

Ω

..

Fig. 7

EXTERNAL CIRCUIT

PROTECTED FROM

OVER TEMPERATURE

(V+ GOES OFF WHEN

TEMP > 125)

OR

RELAY

8.2K

TEMP

SENSOR

GND

V

OUT

FB

SD

+V

IN

+V

IN

10K

5 DEGREE SHUTDOWN FLAG

ERROR

_______

3 5

8

4 7

1

AUX SHUTDOW

INPUT

OFF

ON

Ω

..

AS35

+

-

Fig 6. System Over Temperature Protection

LP2951

Ω

..

Rev. 11/2/00

LP2950/LP2951

SCHEMATIC DIAGRAM

Rev. 11/2/00

LP2950/LP2951

ORDERING INFORMATION

Ordering No. Precision Output Voltage Packages

LP2950AS 1% Adj 8 Lead SOIC

LP2950AS-3.0 1% 3.0V 8 Lead SOIC

LP2950AS-3.3 1% 3.3V 8 Lead SOIC

LP2950AS-5.0 1% 5.0V 8 Lead SOIC

LP2950CS 0.5% Adj 8 Lead SOIC

LP2950CS-3.0 0.5% 3.0V 8 Lead SOIC

LP2950CS-3.3 0.5% 3.3V 8 Lead SOIC

LP2950CS-5.0 0.5% 5.0V 8 Lead SOIC

LP2950AT 1% Adj 3 Lead TO-263

LP2950AT-3.0 1% 3.0V 3 Lead TO-263

LP2950AT-3.3 1% 3.3V 3 Lead TO-263

LP2950AT-5.0 1% 5.0V 3 Lead TO-263

LP2950CT 0.5% Adj 3 Lead TO-263

LP2950CT-3.0 0.5% 3.0V 3 Lead TO-263

LP2950CT-3.3 0.5% 3.3V 3 Lead TO-263

LP2950CT-5.0 0.5% 5.0V 3 Lead TO-263

SIGNAL PROCESSING EXCELLENCE

Sipex Corporation

Headquarters and Main Offices:

22 Linnell Circle

Billerica, MA 01821

TEL: (978) 667-8700

FAX: (978) 670-9001

e-mail: sales@sipex.com

233 South Hillview Drive

Milpitas, CA 95035

TEL: (408) 935-7600

FAX: (408) 934-7500

Sipex Corporation reserves the right to make changes to any products described herein. Sipex does not assume any liability arising out of the application or use of any product or circuit described

hereing; neither does it convey any license under its patent rights nor the rights of others.

Corporation