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 temperature
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 regu-
lator is in the dropout mode (V
OUT
− V
IN
≤
3V). Output
voltage accuracy is guaranteed to
±
5% over load, and tem-
perature extremes.
The LM2990 is short-circuit proof, and thermal shutdown
includes 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
−40˚C to +125˚C.
Features
n
n
n
n
n
n
n
5% output accuracy over entire operating range
Output current in excess of 1A
Dropout voltage typically 0.6V at 1A load
Low quiescent current
Internal short circuit current limit
Internal thermal shutdown with hysteresis
Functional complement to the LM2940 series
Applications
n
Post switcher regulator
n
Local, on-card, regulation
n
Battery operated equipment
Typical Application
01080101
*Required if the regulator is located further than 6 inches from the power supply filter capacitors. A 1 µF solid tantalum or a 10 µF aluminum electrolytic
capacitor is recommended.
**Required for stability. Must be at least a 10 µF aluminum electrolytic or a 1 µF 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 10Ω over the same operating temperature range as the regulator.
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Input Voltage
ESD Susceptibility (Note 2)
Power Dissipation (Note 3)
Junction Temperature (T
Jmax
)
Storage Temperature
−26V to +0.3V
2 kV
Internally Limited
125˚C
−65˚C to +150˚C
Lead Temperature
(Soldering, 10 sec.)
260˚C
Operating Ratings
(Note 1)
Junction Temperature Range (T
J
)
Maximum Input Voltage
(Operational)
−40˚C to +125˚C
−26V
Electrical Characteristics
V
IN
= −5V + V
O(NOM)
(Note 6) , I
O
= 1A, C
O
= 47 µF, unless otherwise specified.
Boldface
limits apply over the entire operat-
ing temperature range, −40˚C
≤
T
J
≤
125˚C, all other limits apply for T
J
= 25˚C.
LM2990-5.0
Parameter
Output Voltage (V
O
)
Conditions
5 mA
≤
I
O
≤
1A
−5
5 mA
≤
I
O
≤
1A
Line Regulation
Load Regulation
Dropout Voltage
Quiescent Current (I
q
)
Short Circuit Current
Maximum Output Current
Ripple Rejection
Output Noise Voltage
Long Term Stability
I
O
= 5 mA,
V
O(NOM)
−1V
>
V
IN
>
−26V
50 mA
≤
I
O
≤
1A
I
O
= 0.1A,
∆V
O
≤
100 mV
I
O
= 1A,
∆V
O
≤
100 mV
I
O
≤
1A
I
O
= 1A, V
IN
= V
O(NOM)
R
L
= 1Ω (Note 7)
(Note 7)
V
ripple
= 1 V
rms
,
ƒ
ripple
= 1 kHz, I
O
= 5 mA
10 Hz–100 kHz, I
O
= 5 mA
1000 Hours
250
2000
750
250
2000
750
µV (max)
ppm
1
0.1
0.6
1
9
1.8
1.8
58
40
0.3
1
5
50
1.5
1.5
50
1
0.1
0.6
1
9
1.8
1.8
58
40
0.3
1
5
50
1.5
1.5
50
mV (max)
V (max)
V (max)
mA (max)
mA (max)
A (min)
A (min)
dB (min)
4
−4.75
−5.25
40
4
Typ
(Note 4)
Limit
(Note 5)
−4.90
−5.10
−5.2
−4.94
−5.46
40
LM2990-5.2
Typ
(Note 4)
Limit
(Note 5)
−5.10
−5.30
V (max)
mV (min)
V
V (max)
V (min)
mV (max)
Units
(Limit)
Electrical Characteristics
V
IN
= −5V + V
O(NOM)
(Note 6) , I
O
= 1A, C
O
= 47 µF, unless otherwise specified.
Boldface
limits apply over the entire operat-
ing temperature range, −40˚C
≤
T
J
≤
125˚C, all other limits apply for T
J
= 25˚C.
LM2990-12
Parameter
Output Voltage (V
O
)
Conditions
5 mA
≤
I
O
≤
1A
−12
5 mA
≤
I
O
≤
1A
Line Regulation
Load Regulation
Dropout Voltage
I
O
= 5 mA,
V
O(NOM)
−1V
>
V
IN
>
−26V
50 mA
≤
I
O
≤
1A
I
O
= 0.1A,
∆V
O
≤
100 mV
I
O
= 1A,
∆V
O
≤
100 mV
3
0.1
0.6
50
0.3
1
3
0.1
0.6
50
0.3
1
mV (max)
V (max)
V (max)
6
−11.40
−12.60
60
6
Typ
(Note 4)
Limit
(Note 5)
−11.76
−12.24
−15
−14.25
−15.75
60
LM2990-15
Typ
(Note 4)
Limit
(Note 5)
−14.70
−15.30
V (max)
V (min)
V
V (max)
V (min)
mV (max)
Units
(Limit)
3
www.national.com
LM2990
Electrical Characteristics
(Continued)
V
IN
= −5V + V
O(NOM)
(Note 6) , I
O
= 1A, C
O
= 47 µF, unless otherwise specified.
Boldface
limits apply over the entire operat-
ing temperature range, −40˚C
≤
T
J
≤
125˚C, all other limits apply for T
J
= 25˚C.
LM2990-12
Parameter
Conditions
I
O
≤
1A
I
O
= 1A, V
IN
= V
O(NOM)
R
L
= 1Ω (Note 7)
(Note 7)
V
ripple
= 1 V
rms
,
ƒ
ripple
= 1 kHz, I
O
= 5 mA
10 Hz–100 kHz, I
O
= 5 mA
1000 Hours
Typ
(Note 4)
1
9
1.2
1.8
52
500
2000
Limit
(Note 5)
5
50
0.9
1.4
42
1500
LM2990-15
Typ
(Note 4)
1
9
1.0
1.8
52
600
2000
Limit
(Note 5)
5
50
0.75
1.4
42
1800
mA (max)
mA (max)
A (min)
A (min)
dB (min)
µV (max)
ppm
Units
(Limit)
Quiescent Current (I
q
)
Short Circuit Current
Maximum Output Current
Ripple Rejection
Output Noise Voltage
Long Term Stability
Note 1:
Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is
intended 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 kΩ resistor.
Note 3:
The maximum power dissipation is a function of T
Jmax
,
θ
JA
, and T
A
. The maximum allowable power dissipation at any ambient temperature is P
D
= (T
Jmax
− T
A
)/θ
JA
. If this dissipation is exceeded, the die temperature will rise above 125˚C, and the LM2990 will eventually go into thermal shutdown at a T
J
of approximately
160˚C. For the LM2990, the junction-to-ambient thermal resistance, is 53˚C/W, 73˚C/W for the TO-263, and the junction-to-case thermal resistance is 3˚C. 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,
θ
JA
is 50˚C/W; with 1 square inch of copper area,
θ
JA
is 37˚C/W; and with 1.6 or more square inches of copper area,
θ
JA
is 32˚C/W.
Note 4:
Typicals are at T
J
= 25˚C 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 con-
ditions 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
模拟与混合信号
