LM2931AZ-5.0/NOPB - NATIONAL SEMICONDUCTOR

LM2931

Series Low Dropout Regulators

General Description

The LM2931 positive voltage regulator features a very low

quiescent current of 1mA or less when supplying 10mA loads.

This unique characteristic and the extremely low input-output

differential required for proper regulation (0.2V for output cur-

rents of 10mA) make the LM2931 the ideal regulator for

standby power systems. Applications include memory stand-

by circuits, CMOS and other low power processor power

supplies as well as systems demanding as much as 100mA

of output current.

Designed originally for automotive applications, the LM2931

and all regulated circuitry are protected from reverse battery

installations or 2 battery jumps. During line transients, such

as a load dump (60V) when the input voltage to the regulator

can momentarily exceed the specified maximum operating

voltage, the regulator will automatically shut down to protect

both internal circuits and the load. The LM2931 cannot be

harmed by temporary mirror-image insertion. Familiar regu-

lator features such as short circuit and thermal overload pro-

tection are also provided.

The LM2931 family includes a fixed 5V output (±3.8% toler-

ance for A grade) or an adjustable output with ON/OFF pin.

Both versions are available in a TO-220 power package,

TO-263 surface mount package, and an 8-lead surface mount

package. The fixed output version is also available in the

TO-92 plastic package.

Features

●Very low quiescent current

●Output current in excess of 100 mA

●Input-output differential less than 0.6V

●Reverse battery protection

●60V load dump protection

●−50V reverse transient protection

●Short circuit protection

●Internal thermal overload protection

●Mirror-image insertion protection

●Available in TO-220, TO-92, TO-263, or SO-8 packages

●Available as adjustable with TTL compatible switch

Connection Diagrams

FIXED VOLTAGE OUTPUT

TO-220 3-Lead Power Package

525406

Front View

TO-263 Surface-Mount Package

525411

Top View

525412

Side View

8-Pin Surface Mount

525407

*NC = Not internally connected. Must be electrically isolated from the rest of

the circuit for the micro SMD package.

Top View

TO-92 Plastic Package

525408

Bottom View

PRODUCTION DATA information is current as of

publication date. Products conform to specifications per

the terms of the Texas Instruments standard warranty.

Production processing does not necessarily include

testing of all parameters.

6-Bump micro SMD

525438

Top View

(Bump Side Down)

micro SMD Laser Mark

525439

ADJUSTABLE OUTPUT VOLTAGE

TO-220 5-Lead Power Package

525409

Front View

TO-263

5-Lead Surface-Mount Package

525413

Top View

525414

Side View

8-Pin Surface Mount

525410

Top View

LM2931

Ordering Information

Output

Voltage

Package

Type

NSC

Drawing

Order

Number

Package

Marking

Transport

Media

8-Pin SOIC Narrow M08A

LM2931AM-5.0 2931AM-5.0 Rail of 95

LM2931AMX-5.0 2931AM-5.0 Reel of 2500

LM2931M-5.0 2931M-5.0 Rail of 95

LM2931MX-5.0 2931M-5.0 Reel of 2500

3-Pin TO-220 T03B LM2931AT-5.0 LM2931AT5.0 Rail of 45

LM2931T-5.0 LM2931T5.0 Rail of 45

3-Pin TO-263 TS3B

LM2931AS-5.0 LM2931AS5.0 Rail of 45

LM2931ASX-5.0 LM2931AS5.0 Reel of 500

LM2931S-5.0 LM2931S5.0 Rail of 45

3-Pin TO-92 Z03A LM2931AZ-5.0 LM2931AZ-5 Box of 1800

LM2931Z-5.0 LM2931Z-5 Box of 1800

Adjustable

3V to 24V

8-Pin SOIC Narrow M08A LM2931CM LM2931CM Rail of 95

LM2931CMX LM2931CM Reel of 2500

5-Pin TO-220 T05A LM2931CT LM2931CT Rail of 45

5-Pin TO-263 TS5B LM2931CS LM2931CS Rail of 45

LM2931

Typical Applications

LM2931 Fixed Output

525404

*Required if regulator is located far from power supply filter.

**C2 must be at least 100 μF to maintain stability. May be increased without bound to maintain regulation during transients. Locate as close as possible to the

regulator. This capacitor must be rated over the same operating temperature range as the regulator. The equivalent series resistance (ESR) of this capacitor is

critical; see curve.

LM2931 Adjustable Output

525405

Note: Using 27k for R1 will automatically compensate for errors in VOUT due to the input bias current of the ADJ pin (approximately 1 μA).

LM2931

Absolute Maximum Ratings (Note 1)

If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/ Distributors for

availability and specifications.

Input Voltage

Operating Range 26V

Overvoltage Protection

LM2931A, LM2931C (Adjustable) 60V

LM2931 50V

Internal Power Dissipation

(Note 2, Note 4) Internally Limited

Operating Ambient Temperature

Range −40°C to +85°C

Maximum Junction Temperature 125°C

Storage Temperature Range −65°C to +150°C

Lead Temp. (Soldering, 10 seconds) 230°C

ESD Tolerance (Note 5) 2000V

Electrical Characteristics for Fixed 3.3V Version

VIN = 14V, IO = 10mA, TJ = 25°C, C2 = 100μF (unless otherwise specified) (Note 2)

Parameter Conditions

LM2931-3.3

Units

Typ Limit

(Note 3)

Output Voltage 3.3 3.465

3.135

VMAX

VMIN

4V ≤ VIN ≤ 26V, IO = 100 mA

−40°C ≤ TJ ≤ 125°C

3.630

2.970

VMAX

VMIN

Line Regulation 4V ≤ VIN ≤ 26V 4 33 mVMAX

Load Regulation 5mA ≤ IO ≤ 100mA 10 50 mVMAX

Output Impedance 100mADC and 10mArms,

100Hz - 10kHz

200 mΩ

Quiescent Current IO ≤ 10mA, 4V ≤ VIN ≤ 26V 0.4 1.0 mAMAX

−40°C ≤ TJ ≤ 125°C

IO = 100mA, VIN = 14V, TJ = 25°C 15 mA

Output Noise Voltage 10Hz -100kHz, COUT = 100μF330 μVrms

Long Term Stability 13 mV/1000 hr

Ripple Rejection fO = 120Hz 80 dB

Dropout Voltage IO = 10mA

IO = 100mA

0.05

0.30

0.2

0.6 VMAX

Maximum Operational Input

Voltage

33 26 VMIN

Maximum Line Transient RL = 500Ω, VO ≤ 5.5V,

T = 1ms, τ ≤ 100ms

70 50 VMIN

Reverse Polarity Input Voltage, DC VO ≥ −0.3V, RL = 500Ω −30 −15 VMIN

Reverse Polarity Input Voltage,

Transient

T = 1ms, τ ≤ 100ms, RL = 500Ω −80 −50 VMIN

LM2931

Electrical Characteristics for Fixed 5V Version

VIN = 14V, IO = 10mA, TJ = 25°C, C2 = 100 μF (unless otherwise specified) (Note 2)

Parameter Conditions

LM2931A-5.0 LM2931-5.0

Units

Typ Limit

(Note 3)Typ Limit

(Note 3)

Output Voltage 5 5.19

4.81

5 5.25

4.75

VMAX

VMIN

6.0V ≤ VIN ≤ 26V, IO = 100mA

−40°C ≤ TJ ≤ 125°C

5.25

4.75

5.5

4.5

VMAX

VMIN

Line Regulation 9V ≤ VIN ≤ 16V

6V ≤ VIN ≤ 26V

30 mVMAX

Load Regulation 5 mA ≤ IO ≤ 100mA 14 50 14 50 mVMAX

Output Impedance 100mADC and 10mArms,

100Hz -10kHz

200 200 mΩ

Quiescent Current IO ≤ 10mA, 6V ≤ VIN ≤ 26V 0.4 1.0 0.4 1.0 mAMAX

−40°C ≤ TJ ≤ 125°C

IO = 100mA, VIN = 14V, TJ = 25°C 15 30 15 mAMAX

Output Noise Voltage 10Hz -100kHz, COUT = 100μF500 500 μVrms

Long Term Stability 20 20 mV/1000

Ripple Rejection fO = 120 Hz 80 55 80 dBMIN

Dropout Voltage IO = 10mA

IO = 100mA

0.05

0.3

0.2

0.6

0.05

0.3

0.2

0.6 VMAX

Maximum Operational Input

Voltage

33 26 33 26 VMIN

Maximum Line Transient RL = 500Ω, VO ≤ 5.5V,

T = 1ms, τ ≤ 100ms 70 60 70 50 VMIN

Reverse Polarity Input Voltage,

VO ≥ −0.3V, RL = 500Ω −30 −15 −30 −15 VMIN

Reverse Polarity Input Voltage,

Transient

T = 1ms, τ ≤ 100ms, RL = 500Ω −80 −50 −80 −50 VMIN

Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Electrical specifications do not apply when operating the device

beyond its rated operating conditions.

Note 2: See circuit in Typical Applications. To ensure constant junction temperature, low duty cycle pulse testing is used.

Note 3: All limits are guaranteed for TJ = 25°C (standard type face) or over the full operating junction temperature range of −40°C to +125°C (bold type face).

Note 4: The maximum power dissipation is a function of maximum junction temperature TJmax, total thermal resistance θJA, and ambient temperature TA. The

maximum allowable power dissipation at any ambient temperature is PD = (TJmax − TA)/θJA. If this dissipation is exceeded, the die temperature will rise above 150°

C and the LM2931 will go into thermal shutdown. For the LM2931 in the TO-92 package, θJA is 195°C/W; in the SO-8 package, θJA is 160°C/W, and in the TO-220

package, θJA is 50°C/W; in the TO-263 package, θJA is 73°C/W; and in the 6-Bump micro SMD package θJA is 290°C/W. If the TO-220 package is used with a

heat sink, θJA is the sum of the package thermal resistance junction-to-case of 3°C/W and the thermal resistance added by the heat sink and thermal interface.

If the TO-263 package is used, the thermal resistance can be reduced by increasing the P.C. board copper area thermally connected to the package: Using 0.5

square inches of copper area, θJA is 50°C/W; with 1 square inch of copper area, θJA is 37°C/W; and with 1.6 or more square inches of copper area, θJA is 32°C/

Note 5: Human body model, 100 pF discharged through 1.5 kΩ.

LM2931

Electrical Characteristics for Adjustable Version

VIN = 14V, VOUT = 3V, IO = 10 mA, TJ = 25°C, R1 = 27k, C2 = 100 μF (unless otherwise specified) (Note 2)

Parameter Conditions Typ Limit Units Limit

Reference Voltage 1.20 1.26 VMAX

1.14 VMIN

IO ≤ 100 mA, −40°C ≤ Tj ≤ 125°C, R1 = 27k 1.32 VMAX

Measured from VOUT to Adjust Pin 1.08 VMIN

Output Voltage Range 24 VMAX

3 VMIN

Line Regulation VOUT + 0.6V ≤ VIN ≤ 26V 0.2 1.5 mV/VMAX

Load Regulation 5 mA ≤ IO ≤ 100 mA 0.3 1 %MAX

Output Impedance 100 mADC and 10 mArms, 100 Hz–10 kHz 40 mΩ/V

Quiescent Current IO = 10 mA 0.4 1 mAMAX

IO = 100 mA 15 mA

During Shutdown RL = 500Ω 0.8 1 mAMAX

Output Noise Voltage 10 Hz–100 kHz 100 μVrms/V

Long Term Stability 0.4 %/1000 hr

Ripple Rejection fO = 120 Hz 0.02 %/V

Dropout Voltage IO ≤ 10 mA 0.05 0.2 VMAX

IO = 100 mA 0.3 0.6 VMAX

Maximum Operational Input

Voltage 33 26 VMIN

Maximum Line Transient IO = 10 mA, Reference Voltage ≤ 1.5V 70 60 VMIN

T = 1 ms, τ ≤ 100 ms

Reverse Polarity Input VO ≥ −0.3V, RL = 500Ω

Voltage, DC −30 −15 VMIN

Reverse Polarity Input T = 1 ms, τ ≤ 100 ms, RL = 500Ω

Voltage, Transient −80 −50 VMIN

On/Off Threshold Voltage VO=3V

On 2.0 1.2 VMAX

Off 2.2 3.25 VMIN

On/Off Threshold Current 20 50 μAMAX

LM2931

Typical Performance Characteristics

Dropout Voltage

525416

Dropout Voltage

525417

Low Voltage Behavior

525418

Output at Voltage Extremes

525419

Line Transient Response

525420

Load Transient Response

525421

LM2931

Peak Output Current

525422

Quiescent Current

525423

Quiescent Current

525424

Quiescent Current

525425

Ripple Rejection

525426

Ripple Rejection

525427

LM2931

Output Impedance

525428

Operation During Load

Dump

525429

Reference Voltage

525430

Maximum Power Dissipation

(SO-8)

525431

Maximum Power Dissipation

(TO-220)

525432

Maximum Power Dissipation

(TO-92)

525433

LM2931

Maximum Power Dissipation

(TO-263) (Note 4)

525434

On/Off Threshold

525435

Output Capacitor ESR

525436

LM2931

Schematic Diagram

525401

LM2931

Application Hints

One of the distinguishing factors of the LM2931 series regulators is the requirement of an output capacitor for device stability. The

value required varies greatly depending upon the application circuit and other factors. Thus some comments on the characteristics

of both capacitors and the regulator are in order.

High frequency characteristics of electrolytic capacitors depend greatly on the type and even the manufacturer. As a result, a value

of capacitance that works well with the LM2931 for one brand or type may not necessary be sufficient with an electrolytic of different

origin. Sometimes actual bench testing, as described later, will be the only means to determine the proper capacitor type and value.

Experience has shown that, as a rule of thumb, the more expensive and higher quality electrolytics generally allow a smaller value

for regulator stability. As an example, while a high-quality 100 μF aluminum electrolytic covers all general application circuits, similar

stability can be obtained with a tantalum electrolytic of only 47μF. This factor of two can generally be applied to any special appli-

cation circuit also.

Another critical characteristic of electrolytics is their performance over temperature. While the LM2931 is designed to operate to

−40°C, the same is not always true with all electrolytics (hot is generally not a problem). The electrolyte in many aluminum types

will freeze around −30°C, reducing their effective value to zero. Since the capacitance is needed for regulator stability, the natural

result is oscillation (and lots of it) at the regulator output. For all application circuits where cold operation is necessary, the output

capacitor must be rated to operate at the minimum temperature. By coincidence, worst-case stability for the LM2931 also occurs

at minimum temperatures. As a result, in applications where the regulator junction temperature will never be less than 25°C, the

output capacitor can be reduced approximately by a factor of two over the value needed for the entire temperature range. To

continue our example with the tantalum electrolytic, a value of only 22μF would probably thus suffice. For high-quality aluminum,

47μF would be adequate in such an application.

Another regulator characteristic that is noteworthy is that stability decreases with higher output currents. This sensible fact has

important connotations. In many applications, the LM2931 is operated at only a few milliamps of output current or less. In such a

circuit, the output capacitor can be further reduced in value. As a rough estimation, a circuit that is required to deliver a maximum

of 10mA of output current from the regulator would need an output capacitor of only half the value compared to the same regulator

required to deliver the full output current of 100mA. If the example of the tantalum capacitor in the circuit rated at 25°C junction

temperature and above were continued to include a maximum of 10mA of output current, then the 22μF output capacitor could be

reduced to only 10μF.

In the case of the LM2931CT adjustable regulator, the minimum value of output capacitance is a function of the output voltage. As

a general rule, the value decreases with higher output voltages, since internal loop gain is reduced.

At this point, the procedure for bench testing the minimum value of an output capacitor in a special application circuit should be

clear. Since worst-case occurs at minimum operating temperatures and maximum operating currents, the entire circuit, including

the electrolytic, should be cooled to the minimum temperature. The input voltage to the regulator should be maintained at 0.6V

above the output to keep internal power dissipation and die heating to a minimum. Worst-case occurs just after input power is

applied and before the die has had a chance to heat up. Once the minimum value of capacitance has been found for the brand

and type of electrolytic in question, the value should be doubled for actual use to account for production variations both in the

capacitor and the regulator. (All the values in this section and the remainder of the data sheet were determined in this fashion.)

LM2931 micro SMD Light Sensitivity

When the LM2931 micro SMD package is exposed to bright sunlight, normal office fluorescent light, and other LED's, it operates

within the guaranteed limits specified in the electrical characteristic table.

Definition of Terms

Dropout Voltage: The input-output voltage differential at which the circuit ceases to regulate against further reduction in input

voltage. Measured when the output voltage has dropped 100 mV from the nominal value obtained at 14V input, dropout voltage is

dependent upon load current and junction temperature.

Input Voltage: The DC voltage applied to the input terminals with respect to ground.

Input-Output Differential: The voltage difference between the unregulated input voltage and the regulated output voltage for which

the regulator will operate.

Line Regulation: The change in output voltage for a change in the input voltage. The measurement is made under conditions of

low dissipation or by using pulse techniques such that the average chip temperature is not significantly affected.

Load Regulation: The change in output voltage for a change in load current at constant chip temperature.

Long Term Stability: Output voltage stability under accelerated life-test conditions after 1000 hours with maximum rated voltage

and junction temperature.

Output Noise Voltage: The rms AC voltage at the output, with constant load and no input ripple, measured over a specified

frequency range.

Quiescent Current: That part of the positive input current that does not contribute to the positive load current. The regulator ground

lead current.

Ripple Rejection: The ratio of the peak-to-peak input ripple voltage to the peak-to-peak output ripple voltage at a specified

frequency.

Temperature Stability of VO: The percentage change in output voltage for a thermal variation from room temperature to either

temperature extreme.

LM2931

Physical Dimensions inches (millimeters) unless otherwise noted

8-Lead Surface Mount Package (M)

NS Package Number M08A

3-Lead TO-220 Plastic Package (T)

NS Package Number T03B

LM2931

5-Lead TO-220 Power Package (T)

NS Package Number T05A

3-Lead TO-263 Surface Mount Package

NS Package Number TS3B

LM2931

5-Lead TO-263 Surface Mount Package

NS Package Number TS5B

3-Lead TO-92 Plastic Package (Z)

NS Package Number Z03A

LM2931

NOTE: UNLESS OTHERWISE SPECIFIED.

1. EPOXY COATING.

2. 63Sn/37Pb EUTECTIC BUMP.

3. RECOMMEND NON-SOLDER MASK DEFINED LANDING PAD.

4. PIN A1 IS ESTABLISHED BY LOWER LEFT CORNER WITH RESPECT TO TEST ORIENTATION PINS ARE NUMBERED COUNTERCLOCKWISE.

5. XXX IN DRAWING NUMBER REPRESENTS PACKAGE SIZE VARIATION WHERE X1 IS PACKAGE WIDTH, X2 IS PACKAGE LENGTH AND X3 IS PACKAGE

HEIGHT.

6. REFERENCE JEDEC REGISTRATION MO-211, VARIATION BC.

6-Bump micro SMD

NS Package Number BPA06HTB

X1 = 0.955 X2 = 1.717 X3 = 0.850

LM2931

Notes

Incorporated

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