Bay Linear
Linear Excellence
100mA Low Dropout Voltage Regulator
LM2931
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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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
Battery Powered Systems
Portable instrumentation
Notebooks Computers
Potable Consumer Equipment
Automotive electronics
SMPS Post-Regulator
Applications
Pin Connection
TO-92
SOT-89
1
BAY
LM2931
OUTPUT
INPUT
GND OUTPUT
Ordering Information
Package
2
3
SOT-89
TO-92
8-SOIC
INPUT
Tolerance
LM2931R-XX
LM2931Z-XX
LM2931M-XX
GROUND
Front View
“XX” Voltage Selection Guide
Vout
3.3V
5.0V
8.0V
8.5V
9.0V
10.0V
12.0V
15.0V
Adjustable
XX Code
33
50
80
85
90
10
12
15
Left Blank
Bottom View
8SOIC (M)
Output
GND
GND
Feedback
1
2
3
4
8
7
6
5
Input
GND
GND
Shutdown
Bay Linear, Inc
2478 Armstrong Street, Livermore, CA 94550 Tel: (925) 989-7144, Fax: (925) 940-9556
www.baylinear.com
LM2931
Absolute Maximum Rating
Parameter
Power Dissipation
Lead Temperature ( Soldering 5 seconds )
Storage Temperature Range
Operating Junction Temperature
Input Supply Voltage
Internally Limited
260
°C
-65
°C
to +150
°C
-55
°C
to +150
°C
-20 to +35V
Electrical Characteristics
T
J
= 25°C , I
O
= 100µA, V
IN
= 14V ( for 2931-15 V
IN
= 16V), C
O
= 100µF; unless otherwise specified)
Parameter
Conditions
MIN
TYP
MAX
Output Voltage
(Fixed Version)
Output Voltage (Fixed Version)
Input Supply Voltage
Output Voltage Temperature
Coefficient
Line Regulation (Note 2)
Load Regulation (Note 2)
Dropout Voltage (Note 4)
Ground Current (Note 5)
-25
°C ≤
T
j
≤
85
°C
Full Operating Temperature
100µA
≤
I
L
≤
100mA, T
j
≤
T
jmax
(Note 1)
13V
≤
V
IN
≤
26V (Note 3)
100µA
≤
I
L
≤
100mA
I
L
= 100µA
I
L
= 100mA
I
L
= 100µA
I
L
= 10mA
I
L
= 100mA
V
IN
= (V
OUT
– 0.5V), I
L
= 100µA
V
OUT
= 0
C
L
= 2.2µF
C
L
= 3.3µF
C
L
= 33µF
I
O
= 10mA, f = 120Hz, C
0
= 100µF
V
IN
= V
O
+ 3V+2Vpp
0.985 [ V
o
]
0.98 [ V
o
]
0.975 [V
o
]
V
o
50
0.1
0.1
60
300
100
0.9
8
110
160
0.05
500
350
120
60
V
o
1.015 [ V
o
]
1.02 [ V
o
]
1.025 [ V
o
]
26
150
0.4
0.3
200
600
150
1.5
12
170
200
0.2
V
V
ppm /
°
C
%
%
mV
µA
mA
mA
µA
mA
%/W
µVrms
UNIT
V
Dropout Ground Current
Current Limit
Thermal Regulation (Note 6)
Output Noise,
10Hz to 100KHz
I
L
= 10mA
Ripple Rejection Ratio
dB
8 pin Versions only (LP2951)
Reference Voltage
Over Temperature (Note 7)
Feedback Pin Bias Current
Reference Voltage Temperature
Coefficient
Feedback Pin Bias Current
Temperature Coefficient
Shutdown Input
Input Logic Voltage
Shutdown Pin Input Current
Regulator Output Current
in Shutdown
(Note 1)
1.21
1.185
1.235
20
50
0.1
1.26
1.285
40
V
ηA
ppm/°C
ηA/°C
Low (Regulator ON)
High (Regulator OFF)
V
S
= 2.4V
V
S
= 26V
(Note 8)
5.0V
≤
V
OUT
≤
15.0V
3.3V
≤
V
OUT
≤
5.0V
2.0V
≤
V
OUT
≤
3.3V
1.3
2
30
450
0.7
50
600
10
20
30
V
µA
µA
Bay Linear, Inc
2478 Armstrong Street, Livermore, CA 94550 Tel: (925) 989-7144, Fax: (925) 940-9556
www.baylinear.com
LM2931
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 T
J
= 25°C, V
IN
= V
O
+1V, I
L
= 100µA and C
L
= 1µF. Additional conditions for the 8-
pin versions are feedback tied to –XX Voltage tap and output tied to output Sense pin ( V
OUT
= XX V) and V
SHUTDOWN
≤
0.8V
Note 2:
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 specification for thermal regulation.
Note 3:
Line regulation for is tested at 150°C for I
L
= 1mA. For I
L
= 100µA and T
J
= 125°C, line regulation is guaranteed by design to 0.2%. for
B2931-15 16V
≤
V
IN
≤
26V.
Note 4:
Dropout voltage is defined as the input to output differential 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 current and
output load current.
Note 6:
Thermal regulation is the change in output voltage at a time T after a change in power dissipation, excluding load or line regulation
effects. Specifications are for a 50 mA load pulse (1.25W) for T = 10ms.
Note 7:
V
REF
≤
V
OUT
≤
(V
IN
–1V), 2.3V
≤
V
IN
≤
26V, 100µA
≤
I
L
≤100mA,
T
J
≤
T
JMAX
Note 8:
V
SHUTDOWN
≥
2V, V
IN
≤
26V, V
OUT
= 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 obtained with a tantalum
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
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 decreases. In most
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: (925) 989-7144, Fax: (925) 940-9556
www.baylinear.com
LM2931
TYPICAL CHARACTERISTICS
QUIESCENT CURRENT
QUIESCENT CURRENT
REFERENCE VOLTAGE
25
QUIESCENT CURRENT (mA)
30
25
20
15
10
5
0
-40
0
40
80
120
0
V
IN
= 14V
REFERENCE VOLTAGE (V)
1.30
1.28
1.26
1.24
1.22
1.20
1.18
1.16
1.14
1.12
1.10
LM2931CT ADJUSTABLE
QUIESCENT CURRENT (mA)
20
15
10
~
~
~
~
I
O
= 50mA
3
2
1
0
I
O
= 0mA
30
60
90
0
3
6
9
12
15
18
21
24
JUNCTION TEMPERATURE (ºC)
OUTPUT CURRENT (mA)
OUTPUT VOLTAGE (V)
DROPOUT VOLTAGE
DROPOUT VOLTAGE
PEAK OUTPUT CURRENT
0.6
INPUT OUTPUT DIFFERENTIAL (V)
0.6
INPUT OUTPUT DIFFERENTIAL (V)
800
500
OUTPUT CURRENT (mA)
0.5
0.4
0.3
0.2
0.1
0
0
40
80
120
JUNCTION TEMPERATURE (ºC)
LOW VOLTAGE BEHAVIOR
I
O
= 50mA
I
O
= 10mA
I
O
= 100mA
0.5
0.4
0.3
0.2
0.1
0
0
50
OUTPUT CURRENT (mA)
MAXIMUM POWER DISSIPATION (TO-220)
T
J
= 25ºC
400
300
200
100
0
T
J
= 85ºC
T
J
= -40ºC
100
0
10
20
30
INPUT VOLTAGE (V)
MAXIMUM POWER DISSIPATION (TO-92)
6.0
LM2931 5.0
I
O
= 100 mA
POWER DISSIPATION (W)
22
20
18
16
14
12
10
8
6
4
2
0
2.0
3.0
4.0
5.0
6.0
INFINITE HEAT SINK
POWER DISSIPATION (W)
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0
10 20 30 40 50 60 70 80 90
AMBIENT TEMPERATURE (ºC)
0.4" LENGTH
FROMPC BOARD
0.125" LEAD LENGTH
FROM PC BOARD
5.0
OUTPUT VOLTAGE (V)
4.0
10 ºC/W HEAT SINK
3.0
2.0
NO HEAT SINK
1.0
0 10 20 30 40 50 60 70 80 90 100
AMBIENT TEMPERATURE (ºC)
INPUT VOLTAGE (V)
MAXIMUM POWER DISSIPATION (SO-
8)
MAXIMUM POWER DISSIPATION
OPERATION DURING LOAD DUMP
1.0
0.9
POWER DISSIPATION (W)
OUTPUT IMPEDANCE (Ω)
Ω)
10
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0
5
10
15
20
25
30
AMBIENT TEMPERATURE (ºC)
1
OUTPUT
VOLTAGE (V)
LM2931-
5.0
I
O
= 10mA
70
60
50
40
30
20
10
0
~
~
6
4
2
0
-2
-100
0.1
0.01
0
30
60
90
120
150
FREQUENCY (Hz)
OUTPUT
VOLTAGE (V)
C
O
= 100µF
R
L
= 500W
~
~
0
100
200
300
400
500
TIME (ms)
Bay Linear, Inc
2478 Armstrong Street, Livermore, CA 94550 Tel: (925) 989-7144, Fax: (925) 940-9556
www.baylinear.com
Programming Basics
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