June 1999
LM2990
Negative Low Dropout Regulator
General Description
The LM2990 is a three-terminal, low dropout, 1 ampere negative voltage regulator available with fixed output voltages 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 regulator is in the dropout mode (VOUT − V IN ≤ 3V). Output voltage accuracy is guaranteed to ±5% over load,
and temperature 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 −40ÊC to +125ÊC.
Features
n5% output accuracy over entire operating range
nOutput current in excess of 1A
nDropout voltage typically 0.6V at 1A load
nLow quiescent current
nInternal short circuit current limit
nInternal thermal shutdown with hysteresis
nFunctional complement to the LM2940 series
Applications
nPost switcher regulator
nLocal, on-card, regulation
nBattery operated equipment
Typical Application
DS010801-1
*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 electrolyt ic 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.
Ordering Information and Connection Diagrams
Temperature |
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Output Voltage |
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Package |
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Range |
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-5.0 |
-5.2 |
-12 |
-15 |
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−40ÊC to |
LM2990T-5.0 |
LM2990T-5.2 |
LM2990T-12 |
LM2990T-15 |
TO-220 |
+125ÊC |
LM2990S-5.0 |
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LM2990S-12 |
LM2990S-15 |
TO-263 |
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−55ÊC to |
LM2990J-5.0-QML |
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LM2990J-12-QML |
LM2990J-15-QML |
J16A |
+125ÊC |
5962-9571101QEA |
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5962-9571001QEA |
5962-9570901QEA |
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LM2990WG5.0-QML |
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WG16A |
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5962-9571101QXA |
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Regulator Dropout Low Negative LM2990
© 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
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
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 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.
Storage Temperature |
−65ÊC to +150ÊC |
Lead Temperature |
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(Soldering, 10 sec.) |
260ÊC |
Input Voltage |
−26V to +0.3V |
Operating Ratings(Note 1) |
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ESD Susceptibility (Note 2) |
2 kV |
Junction Temperature Range (TJ) |
−40ÊC to +125ÊC |
Power Dissipation (Note 3) |
Internally Limited |
Maximum Input Voltage (Operational) |
−26V |
Junction Temperature (TJmax) |
125ÊC |
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Electrical Characteristics
VIN = −5V + V O(NOM) (Note 6) , IO = 1A, CO = 47 µF, unless otherwise specified. Boldface limits apply over the entire operating temperature range, −40ÊC ≤ TJ ≤ 125ÊC, all other limits apply for TJ = 25ÊC.
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LM2990-5.0 |
LM2990-5.2 |
Units |
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(Limit) |
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Parameter |
Conditions |
Typ |
Limit |
Typ |
Limit |
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(Note 4) |
(Note 5) |
(Note 4) |
(Note 5) |
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Output Voltage (VO) |
5 mA ≤ IO ≤ 1A |
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−4.90 |
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−5.10 |
V (max) |
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−5.10 |
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−5.30 |
mV (min) |
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−5 |
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−5.2 |
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V |
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5 mA ≤ IO ≤ 1A |
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−4.75 |
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−4.94 |
V (max) |
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−5.25 |
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−5.46 |
V (min) |
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Line Regulation |
IO = 5 mA, |
4 |
40 |
4 |
40 |
mV (max) |
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VO(NOM) −1V > VIN > −26V |
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Load Regulation |
50 mA ≤ IO ≤ 1A |
1 |
40 |
1 |
40 |
mV (max) |
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Dropout Voltage |
IO = 0.1A, VO ≤ 100 mV |
0.1 |
0.3 |
0.1 |
0.3 |
V (max) |
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IO = 1A, VO ≤ 100 mV |
0.6 |
1 |
0.6 |
1 |
V (max) |
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Quiescent Current (Iq) |
IO ≤ 1A |
1 |
5 |
1 |
5 |
mA (max) |
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IO = 1A, VIN = VO(NOM) |
9 |
50 |
9 |
50 |
mA (max) |
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Short Circuit Current |
RL = 1Ω (Note 7) |
1.8 |
1.5 |
1.8 |
1.5 |
A (min) |
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Maximum Output Current |
(Note 7) |
1.8 |
1.5 |
1.8 |
1.5 |
A (min) |
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Ripple Rejection |
Vripple = 1 Vrms, |
58 |
50 |
58 |
50 |
dB (min) |
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¦ripple = 1 kHz, IO = 5 mA |
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Output Noise Voltage |
10 Hz±100 kHz, IO = 5 mA |
250 |
750 |
250 |
750 |
µV (max) |
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Long Term Stability |
1000 Hours |
2000 |
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2000 |
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ppm |
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Electrical Characteristics
VIN = −5V + V O(NOM) (Note 6) , IO = 1A, CO = 47 µF, unless otherwise specified. Boldface limits apply over the entire operating temperature range, −40ÊC ≤ TJ ≤ 125ÊC, all other limits apply for TJ = 25ÊC.
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LM2990-12 |
LM2990-15 |
Units |
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(Limit) |
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Parameter |
Conditions |
Typ |
Limit |
Typ |
Limit |
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(Note 4) |
(Note 5) |
(Note 4) |
(Note 5) |
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Output Voltage (VO) |
5 mA ≤ IO ≤ 1A |
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−11.76 |
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−14.70 |
V (max) |
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−12.24 |
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−15.30 |
V (min) |
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−12 |
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−15 |
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V |
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5 mA ≤ IO ≤ 1A |
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−11.40 |
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−14.25 |
V (max) |
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−12.60 |
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−15.75 |
V (min) |
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Line Regulation |
IO = 5 mA, |
6 |
60 |
6 |
60 |
mV (max) |
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VO(NOM) −1V > VIN > −26V |
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Load Regulation |
50 mA ≤ IO ≤ 1A |
3 |
50 |
3 |
50 |
mV (max) |
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Dropout Voltage |
IO = 0.1A, VO ≤ 100 mV |
0.1 |
0.3 |
0.1 |
0.3 |
V (max) |
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IO = 1A, VO ≤ 100 mV |
0.6 |
1 |
0.6 |
1 |
V (max) |
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Quiescent Current (Iq) |
IO ≤ 1A |
1 |
5 |
1 |
5 |
mA (max) |
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IO = 1A, VIN = VO(NOM) |
9 |
50 |
9 |
50 |
mA (max) |
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3 |
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Electrical Characteristics (Continued)
VIN = −5V + V O(NOM) (Note 6) , IO |
= 1A, CO = 47 µF, unless otherwise specified. Boldface limits apply over the entire operat- |
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ing temperature range, −40ÊC ≤ TJ |
≤ 125ÊC, all other limits apply for TJ = 25ÊC. |
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LM2990-12 |
LM2990-15 |
Units |
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(Limit) |
Parameter |
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Conditions |
Typ |
Limit |
Typ |
Limit |
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(Note 4) |
(Note 5) |
(Note 4) |
(Note 5) |
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Short Circuit Current |
RL = 1Ω (Note 7) |
1.2 |
0.9 |
1.0 |
0.75 |
A (min) |
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Maximum Output Current |
(Note 7) |
1.8 |
1.4 |
1.8 |
1.4 |
A (min) |
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Ripple Rejection |
Vripple = 1 Vrms, |
52 |
42 |
52 |
42 |
dB (min) |
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¦ripple = 1 kHz, IO = 5 mA |
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Output Noise Voltage |
10 Hz±100 kHz, IO = 5 mA |
500 |
1500 |
600 |
1800 |
µV (max) |
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Long Term Stability |
1000 Hours |
2000 |
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2000 |
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ppm |
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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 TJmax, θJA, and TA. The maximum allowable power dissipation at any ambient temperature is PD = (TJmax − T A)/θJA. If this dissipation is exceeded, the die temperature will rise above 125ÊC, and the LM2990 will eventually go into thermal shutdown at a TJ of approximately 160ÊC. For the LM2990, the junction-to-ambient thermal resistance, is 53ÊC/W, 73ÊC/W for the TO-263, and the junction-to-case thermal resistance i s 3ÊC. 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 50ÊC/W; with 1 square inch of copper area, θJA is 37ÊC/W; and with 1.6 or more square inches of copper area, θJA is 32ÊC/W.
Note 4: Typicals are at TJ = 25ÊC and represent the most likely parametric norm.
Note 5: Limits are guaranteed and 100% production tested.
Note 6: VO(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 lev el. 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 (VO + 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 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 accellerated 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 VO: The percentage change in output voltage for a thermal variation from room temperature to either temperature extreme.
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