LM2990
Negative Low Dropout Regulator
General Description
The LM2990 is a three-terminal, low dropout, 1 ampere
negative voltage regulator available with fixed output volt-
ages of -5, -5.2, -12, and -15V.
The LM2990 uses new circuit design techniques to provide
low dropout and low quiescent current. The dropout voltage
at 1A load current is typically 0.6V and a guaranteed
worst-case maximum of 1V over the entire operating tem-
perature range. The quiescent current is typically 1 mA with
1A load current and an input-output voltage differential
greater than 3V. A unique circuit design of the internal bias
supply limits the quiescent current to only 9 mA (typical)
when the regulator is in the dropout mode (V
OUT
- V
IN
3V).
Output voltage accuracy is guaranteed to
5% over load,
and temperature extremes.
The LM2990 is short-circuit proof, and thermal shutdown in-
cludes hysteresis to enhance the reliability of the device
when overloaded for an extended period of time. The
LM2990 is available in a 3-lead TO-220 package and is rated
for operation over the automotive temperature range of
-40C to +125C.
Features
n
5% output accuracy over entire operating range
n
Output current in excess of 1A
n
Dropout voltage typically 0.6V at 1A load
n
Low quiescent current
n
Internal short circuit current limit
n
Internal thermal shutdown with hysteresis
n
Functional complement to the LM2940 series
Applications
n
Post switcher regulator
n
Local, on-card, regulation
n
Battery operated equipment
Typical Application
Ordering Information and Connection Diagrams
Temperature
Range
Output Voltage
Package
-5.0
-5.2
-12
-15
-40C to
+125C
LM2990T-5.0
LM2990T-5.2
LM2990T-12
LM2990T-15
TO-220
LM2990S-5.0
LM2990S-12
LM2990S-15
TO-263
-55C to
+125C
LM2990J-5.0-QML
5962-9571101QEA
LM2990J-12-QML
5962-9571001QEA
LM2990J-15-QML
5962-9570901QEA
J16A
LM2990WG5.0-QML
5962-9571101QXA
WG16A
DS010801-1
*Required if the regulator is located further than 6 inches from the power supply filter capacitors. A 1 F solid tantalum or a 10 F aluminum electrolytic
capacitor is recommended.
*
*
Required for stability. Must be at least a 10 F aluminum electrolytic or a 1 F solid tantalum to maintain stability. May be increased without bound to
maintain regulation during transients. Locate the capacitor as close as possible to the regulator. The equivalent series resistance (ESR) is critical, and
should be less than 10
over the same operating temperature range as the regulator.
June 1999
LM2990
Negative
Low
Dropout
Regulator
1999 National Semiconductor Corporation
DS010801
www.national.com
Ordering Information and
Connection Diagrams
(Continued)
3-Lead TO-220
DS010801-2
Front View
Order Number LM2990T-5.0, LM2990T-5.2, LM2990T-12
or LM2990T-15
See NS Package Number T03B
TO-263 Surface-Mount Package
DS010801-11
Top View
DS010801-12
Side View
Order Number LM2990S-5.0, LM2990S-12 or
LM2990S-15
See NS Package Number TS3B
16-Lead Ceramic Dual-in-Line Package
DS010801-33
Top View
Order Number
LM2990J-5.0-QML (5962-9571101QEA),
LM2990J-12-QML (5962-9571001QEA), or
LM2990J-15-QML (5962-9570901QEA),
See NS Package Number J16A
16-Lead Ceramic Surface Mount Package
DS010801-34
Top View
Order Number
LM2990WG5.0-QML (5962-9571101QXEA)
See NS Package Number WG16A
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2
Absolute Maximum Ratings
(Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Input Voltage
-26V to +0.3V
ESD Susceptibility (Note 2)
2 kV
Power Dissipation (Note 3)
Internally Limited
Junction Temperature (T
Jmax
)
125C
Storage Temperature
-65C to +150C
Lead Temperature
(Soldering, 10 sec.)
260C
Operating Ratings
(Note 1)
Junction Temperature Range (T
J
)
-40C to +125C
Maximum Input Voltage (Operational)
-26V
Electrical Characteristics
V
IN
= -5V + V
O(NOM)
(Note 6) , I
O
= 1A, C
O
= 47 F, unless otherwise specified. Boldface limits apply over the entire operat-
ing temperature range, -40C
T
J
125C, all other limits apply for T
J
= 25C.
LM2990-5.0
LM2990-5.2
Units
(Limit)
Parameter
Conditions
Typ
Limit
Typ
Limit
(Note 4)
(Note 5)
(Note 4)
(Note 5)
Output Voltage (V
O
)
5 mA
I
O
1A
-5
-4.90
-5.2
-5.10
V (max)
-5.10
-5.30
mV (min)
V
5 mA
I
O
1A
-4.75
-4.94
V (max)
-5.25
-5.46
V (min)
Line Regulation
I
O
= 5 mA,
4
40
4
40
mV (max)
V
O(NOM)
-1V
>
V
IN
>
-26V
Load Regulation
50 mA
I
O
1A
1
40
1
40
mV (max)
Dropout Voltage
I
O
= 0.1A,
V
O
100 mV
0.1
0.3
0.1
0.3
V (max)
I
O
= 1A,
V
O
100 mV
0.6
1
0.6
1
V (max)
Quiescent Current (I
q
)
I
O
1A
1
5
1
5
mA (max)
I
O
= 1A, V
IN
= V
O(NOM)
9
50
9
50
mA (max)
Short Circuit Current
R
L
= 1
(Note 7)
1.8
1.5
1.8
1.5
A (min)
Maximum Output Current
(Note 7)
1.8
1.5
1.8
1.5
A (min)
Ripple Rejection
V
ripple
= 1 V
rms
,
58
50
58
50
dB (min)
ripple
= 1 kHz, I
O
= 5 mA
Output Noise Voltage
10 Hz100 kHz, I
O
= 5 mA
250
750
250
750
V (max)
Long Term Stability
1000 Hours
2000
2000
ppm
Electrical Characteristics
V
IN
= -5V + V
O(NOM)
(Note 6) , I
O
= 1A, C
O
= 47 F, unless otherwise specified. Boldface limits apply over the entire operat-
ing temperature range, -40C
T
J
125C, all other limits apply for T
J
= 25C.
LM2990-12
LM2990-15
Units
(Limit)
Parameter
Conditions
Typ
Limit
Typ
Limit
(Note 4)
(Note 5)
(Note 4)
(Note 5)
Output Voltage (V
O
)
5 mA
I
O
1A
-12
-11.76
-15
-14.70
V (max)
-12.24
-15.30
V (min)
V
5 mA
I
O
1A
-11.40
-14.25
V (max)
-12.60
-15.75
V (min)
Line Regulation
I
O
= 5 mA,
6
60
6
60
mV (max)
V
O(NOM)
-1V
>
V
IN
>
-26V
Load Regulation
50 mA
I
O
1A
3
50
3
50
mV (max)
Dropout Voltage
I
O
= 0.1A,
V
O
100 mV
0.1
0.3
0.1
0.3
V (max)
I
O
= 1A,
V
O
100 mV
0.6
1
0.6
1
V (max)
Quiescent Current (I
q
)
I
O
1A
1
5
1
5
mA (max)
I
O
= 1A, V
IN
= V
O(NOM)
9
50
9
50
mA (max)
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3
Electrical Characteristics
(Continued)
V
IN
= -5V + V
O(NOM)
(Note 6) , I
O
= 1A, C
O
= 47 F, unless otherwise specified. Boldface limits apply over the entire operat-
ing temperature range, -40C
T
J
125C, all other limits apply for T
J
= 25C.
LM2990-12
LM2990-15
Units
(Limit)
Parameter
Conditions
Typ
Limit
Typ
Limit
(Note 4)
(Note 5)
(Note 4)
(Note 5)
Short Circuit Current
R
L
= 1
(Note 7)
1.2
0.9
1.0
0.75
A (min)
Maximum Output Current
(Note 7)
1.8
1.4
1.8
1.4
A (min)
Ripple Rejection
V
ripple
= 1 V
rms
,
52
42
52
42
dB (min)
ripple
= 1 kHz, I
O
= 5 mA
Output Noise Voltage
10 Hz100 kHz, I
O
= 5 mA
500
1500
600
1800
V (max)
Long Term Stability
1000 Hours
2000
2000
ppm
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is in-
tended to be functional, but do not guarantee specific performance limits. For guaranteed specifications and test conditions, see the Electrical Characteristics.
Note 2: Human body model, 100 pF discharged through a 1.5 k
resistor.
Note 3: The maximum power dissipation is a function of T
Jmax
,
JA
, and T
A
. The maximum allowable power dissipation at any ambient temperature is P
D
= (T
Jmax
- T
A
)/
JA
. If this dissipation is exceeded, the die temperature will rise above 125C, and the LM2990 will eventually go into thermal shutdown at a T
J
of approximately
160C. For the LM2990, the junction-to-ambient thermal resistance, is 53C/W, 73C/W for the TO-263, and the junction-to-case thermal resistance is 3C. 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,
JA
is 50C/W; with 1 square inch of copper area,
JA
is 37C/W; and with 1.6 or more square inches of copper area,
JA
is 32C/W.
Note 4: Typicals are at T
J
= 25C and represent the most likely parametric norm.
Note 5: Limits are guaranteed and 100% production tested.
Note 6: V
O(NOM)
is the nominal (typical) regulator output voltage, -5V, -5.2V, -12V or -15V.
Note 7: The short circuit current is less than the maximum output current with the -12V and -15V versions due to internal foldback current limiting. The -5V and
-5.2V versions, tested with a lower input voltage, does not reach the foldback current limit and therefore conducts a higher short circuit current level. If the LM2990
output is pulled above ground, the maximum allowed current sunk back into the LM2990 is 1.5A.
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 (V
O
+
5V) 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 volt-
age 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 condi-
tions of low dissipation or by using pulse techniques such
that the average chip temperature is not significantly af-
fected.
Load Regulation: The change in output voltage for a
change in load current at constant chip temperature.
Long Term Stability: Output voltage stability under accelle-
rated 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.
Temperature Stability of V
O
: The percentage change in
output voltage for a thermal variation from room temperature
to either temperature extreme.
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4
Typical Performance Characteristics
Dropout Voltage
DS010801-14
Normalized Output Voltage
DS010801-15
LM2990-5.0 and LM2990-5.2
Quiescent Current
DS010801-16
LM2990-12
Quiescent Current
DS010801-17
LM2990-15
Quiescent Current
DS010801-18
LM2990-5 and LM2990-5.2
Low Voltage Behavior
DS010801-19
LM2990-5 and LM2990-5.2
Line Transient Response
DS010801-20
LM2990-5 and LM2990-5.2
Load Transient Response
DS010801-21
LM2990-12 and LM2990-15
Low Voltage Behavior
DS010801-22
LM2990-12 and LM2990-15
Line Transient Response
DS010801-23
LM2990-12 and LM2990-15
Load Transient Response
DS010801-24
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