Bay Linear LM2931 Service Manual

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Bay Linear

Bay Linear

Bay LinearBay Linear

Linear Excellenc e

100mA Low Dropout Voltage Regulator

Description

The Bay Linear LM2931 are low power voltage regulators
designed for a wide range of applications. They are an
excellent choice for use in Battery Powered applications. The
LM2931 feature low quiescent current (100 µA Typ.) and low
dropout of only 60mV at light loads and 300mV (typ.) at
100mA. The LM2931 has tight initial tolerance of 0.5% typ.,
extremely good load and line regulation of 0.05% typ. and very
low output temperature coefficient.

The Bay Linear LM2931 is available as a fixed voltage
regulator and as an adjustable regulator in TO-92 and 8SOIC
packages. The Bay Linear LM2931 in an 8SOIC package has
an adjustable output voltage from 3V to 24V, programmed
with a pair of external resistor. The logic compatible shutdown
enables the regulator to be switched ON and OFF.

Features

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Applications

• Battery Powered Systems

• Portable instrumentation

• Notebooks Computers

• Potable Consumer Equipment

• Automotive electronics

• SMPS Post-Regulator

Pin Connection

SOT-89

SOT-89

SOT-89

BAY

BAY

BAY

LM2931

LM2931

LM2931

GND

GND

GND

INPUT

INPUT

INPUT

OUTPUT

OUTPUT

OUTPUT

Front View

Front View

Front View

8SOIC (M)

Output

GND

GND

Feedback

TO-92

TO-92

TO-92

2

2

2

13

13

13

OUTPUT

OUTPUT

OUTPUT

GROUND

GROUND

GROUND

Bott om View

Bott om View

Bott om View

1

2

3

4

8

7

6

5

INPUT

INPUT

INPUT

Input

GND
GND

Shutdown

Ordering Information

Package Tolerance

SOT-89
TO-92
8-SOIC

“XX” Voltage Selection Guide

Vout XX Code

3.3V

5.0V

8.0V

8.5V

9.0V

10.0V

12.0V

15.0V
Adjustable

Guaranteed 100mA Output
Fixed Versions 3.3V, 50.V, 8.0
Very Low Quiescent Current
Low Dropout Voltage
Extremely Tight Load and Line

Regulation
Very Low Temperature Coefficient
Current and Thermal Limiting
Reverse Battery Protection of –20V
Transient protection of 60V
Output programmable from 3V to 24V

LM2931R-XX
LM2931Z-XX
LM2931M-XX

33
50
80
85
90
10
12
15
Left Blank

LM2931

Bay Linear, Inc

2478 Armstrong Street, Livermore, CA 94550 Tel: [phone], Fax: [phone] www.baylinear.com

LM2931

Absolute Maximum Rating

Parameter

Power Dissipation Internally Limited
Lead Temperature ( Soldering 5 seconds )
Storage Temperature Range
Operating Junction Temperatur e
Input Supply Voltage -20 to +35V

260 °C

-65 °C to +150 °C

-55 °C to +150 °C

Electrical Characteristics

TJ = 25°C , IO = 100µA, VIN = 14V ( for 2931-15 VIN = 16V), CO = 100µF; unless otherwise specified)

Parameter Conditions MIN TYP MAX UNIT

Output Voltage
(Fixed Version)

Output Voltage (Fixed Versi on)

-25 °C ≤ T
Full Operating Temperature

100µA ≤ I

≤

85 °C

j

≤

100mA, T

L

≤ T

j

jmax

0.985 [ V

0.98 [ V

0.975 [Vo ] Vo 1.025 [ Vo ]

]

o

]

o

1.015 [ Vo ]

V

o

1.02 [ V

]

o

Input Supply Voltage 26 V
Output Voltage Temperature

(Note 1) 50 150

Coefficient
Line Regulation (Note 2)
Load Regulation (Note 2)
Dropout Voltage (Note 4)

Ground Current (Note 5)

Dropout Ground Current
Current Limit V

13V ≤ V
100µA ≤ I

= 100µA

I

L

≤ 26V (Note 3)

IN

≤

100mA

L

IL = 100mA

= 100µA

I

L

IL = 10mA

= 100mA

I

L

= (V

V

IN
OUT

– 0.5V), IL = 100µA

OUT

= 0 160 200 mA

0.1 0.4 %

0.1 0.3 %
60

300

100

0.9
8

200
600

150

1.5
12

110 170

Thermal Regulation (Note 6) 0.05 0.2 % / W
Output Noise,

10Hz to 100KHz

= 10mA

I

L

Ripple Rejection Ratio

C

= 2.2µF

L

= 3.3µF

C

L

C

= 33µF

L

= 10mA, f = 120Hz, C0 = 100µF

I

O

500

350
120

60 dB

VIN = VO + 3V+2Vpp

8 pin Versions only (LP2951)

Reference Voltage

Over Temperature (Note 7)
Feedback Pin Bias Current 20 40
Reference Voltage Temperature

(Note 1) 50
Coefficient
Feedback Pin Bias Current

0.1

Temperature Coefficient

Shutdown I nput

Input Logic Voltage Low (Regulator ON)

High (Regulator OFF)
Shutdown Pin Input Current VS = 2.4V

VS = 26V
Regulator Output Current
in Shutdown

(Note 8)

5.0V ≤ V

3.3V ≤ V

2.0V ≤ V

OUT
OUT
OUT

≤

15.0V

≤

5.0V

≤

3.3V

1.21

1.235 1.26

1.185

1.3 0.7 V

2

30

450

1.285

50

600

10
20
30

Bay Linear, Inc

2478 Armstrong Street, Livermore, CA 94550 Tel: [phone], Fax: [phone] www.baylinear.com

V

V

ppm / ° C

mV

µ

A
mA
mA

µ

A

µ

Vrms

V

η

A

ppm/°C

ηA/°

C

µ

A

µ

A

OUT

= XX V) and V

SHUTDOWN

LM2931

≤ 0.8V

decreases. In most

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 sp ecified all limits guaranteed for T

pin versions are feedback tied to –XX Voltage tap and output tied to output Sense pin ( V

Note 2:

Regulation is measured at constant junction temperature , using pulse test ing with a low duty cycle. Changes in output voltage due to

heating effects are covered under specification for th ermal regulation.

Note 3:

Line regulation for is tested at 150°C for I

B2931-15 16V ≤ V

Note 4:

Dropout voltage is defined as the input to output differentia l at which the output voltage drops 2% below its nominal value measured at

1V differential .

Note 5:

Ground pin Current is the regulator quiescent current. The total current drawn from the source is the sum of the ground pin curr e nt an d

output load current.

Note 6:

Thermal regulation is the change in output voltage at a time T a f ter a change in power dissipation, exclu d ing load or line regulation

effects. Specifications are for a 50 mA load pulse (1.25W) for T = 10ms.

Note 7:

V

Note 8:

REF

V

SHUTDOWN

≤ 26V.

IN

≤ V

≤ (V

OUT

IN

≥ 2V, VIN ≤ 26V, V

–1V), 2.3V ≤ VIN ≤ 26V, 100µA ≤ IL ≤100mA, T

OUT

= 1mA. For IL = 100µA and TJ = 125°C, line regulation is guarant eed by design to 0.2%. for

L

= 0

Application Hints

The LM2931 requires an output capacitor for device
stability. The value required varies greatly
depending upon the application circuit and other
factors. The high frequency characteristics of
electrolytic capacitors depend greatly on the type and
also on the manufacturer. Sometimes only bench
testing is the only means to determine the proper
capacitor type and value. The high quality 100 µF
aluminum electrolytic covers all general application
circuits, this stability can be o btained with a ta ntalu m
electrolytic value of 47 µF.

Another critical point of electrolytic characteristics is
its performance over temperature. The LM2931 is
designed to operate starting at -40°C which may not
be true in the case of electrolytic. Higher
temperatures generally no problem. The electrolytic.
type in aluminum will freeze around -30°C. This
could cause an oscillation at output of regulator. At a
lower temperature requirement by many applications
the capacitor should maintain its performance. So as
a result, for an application which regulator junction
temperature does not exceed 25°C, the output
capacitor can be reduced by the

= 25°C, VIN = VO +1V, IL = 100µA and CL = 1µF. Additional conditions for the 8-

J

≤ T

J

JMAX

factor of two over the value needed for the entire
temperature range.

Other points with linear regulators are that the twitch
higher output current stability
applications the LM2931 is operating at few
milliamps. In these applications the output capacitance
can be further reduced. For example, when the
regulator is running at 10mA output current the output
capacitance value is half compared to the same
regulator that is running at 100 mA.
With the LM2931 adjustable regulator, the minimum
value of output capacitance is a function of the output
voltage. The value decreases with higher output
voltages, since the internal loop gain is reduced.

The worst case occurs at the lower temperature and
maximum operating currents, the entire circuit and the
electrolytic, should be cooled down to the minimum
temperature. The minimum of 0.6 volts required at
the input of regulator above the output to keep the
power dissipation and die heating to its minimum.
After the value for the capacitor has been determined
for actual use, the value should be doubled.

Bay Linear, Inc

2478 Armstrong Street, Livermore, CA 94550 Tel: [phone], Fax: [phone] www.baylinear.com