LM4871LD NOPB - NATIONAL SEMICONDUCTOR

LM2990

LM2990 Negative Low Dropout Regulator

Literature Number: SNVS093C

LM2990

August 31, 2010

Negative Low Dropout Regulator

General Description

The LM2990 is a three-terminal, low dropout, 1 ampere neg-

ative 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 − VIN ≤ 3V). Output voltage ac-

curacy 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 opera-

tion over the automotive temperature range of −40°C to +125°

Features

■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

■Post switcher regulator

■Local, on-card, regulation

■Battery operated equipment

Typical Application

1080101

*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.

Ordering Information and Connection Diagrams

Temperature

Range

Output Voltage Package

-5.0 -5.2 -12 -15

−40°C to

+125°C

LM2990T-5.0 LM2990T-5.2 LM2990T-12 LM2990T-15 TO-220

LM2990S-5.0 LM2990S-12 LM2990S-15 TO-263

−55°C to

+125°C

LM2990J-5.0-QML

5962-9571101QEA

LM2990J-12-QML

5962-9571001QEA

LM2990J-15-QML

5962-9570901QEA J16A

LM2990WG5.0-QML

5962-9571101QXA

WG16A

LM2990 Negative Low Dropout Regulator

3-Lead TO-220

1080102

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

1080111

Top View

1080112

Side View

Order Number LM2990S-5.0, LM2990S-12 or LM2990S-15

See NS Package Number TS3B

16-Lead Ceramic Dual-in-Line Package

1080133

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

1080134

Top View

Order Number

LM2990WG5.0-QML (5962-9571101QXEA)

See NS Package Number WG16A

www.national.com 2

LM2990

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 (TJmax)125°C

Storage Temperature −65°C to +150°C

Soldering Temperature

TO-220 (T), Wave 260°C, 10 sec

TO-263 (S) 235°C, 30 sec

Operating Ratings (Note 1)

Junction Temperature Range (TJ)−40°C to +125°C

Maximum Input Voltage (Operational) −26V

Electrical Characteristics

VIN = −5V + VO(NOM) (Note 6) , IO = 1A, CO = 47 μF, unless otherwise specified. Boldface limits apply over the entire operating

temperature range, −40°C ≤ TJ ≤ 125°C, all other limits apply for TJ = 25°C.

LM2990-5.0 LM2990-5.2 Units

(Limit)

Parameter Conditions Typ Limit Typ Limit

(Note 4) (Note 5) (Note 4) (Note 5)

Output Voltage (VO)5 mA ≤ IO ≤ 1A

−5

−4.90

−5.2

−5.10 V (max)

−5.10 −5.30 mV (min)

5 mA ≤ IO ≤ 1A −4.75 −4.94 V (max)

−5.25 −5.46 V (min)

Line Regulation IO = 5 mA, 4 40 4 40 mV (max)

VO(NOM) −1V > VIN > −26V

Load Regulation 50 mA ≤ IO ≤ 1A 1 40 1 40 mV (max)

Dropout Voltage IO = 0.1A, ΔVO ≤ 100 mV 0.1 0.3 0.1 0.3 V (max)

IO = 1A, ΔVO ≤ 100 mV 0.6 10.6 1V (max)

Quiescent Current (Iq)IO ≤ 1A 1 5 1 5 mA (max)

IO = 1A, VIN = VO(NOM) 9 50 9 50 mA (max)

Short Circuit Current RL = 1Ω (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 Vripple = 1 Vrms,58 50 58 50 dB (min)

ƒripple = 1 kHz, IO = 5 mA

Output Noise Voltage 10 Hz–100 kHz, IO = 5 mA 250 750 250 750 μV (max)

Long Term Stability 1000 Hours 2000 2000 ppm

Electrical Characteristics

VIN = −5V + VO(NOM) (Note 6) , IO = 1A, CO = 47 μF, unless otherwise specified. Boldface limits apply over the entire operating

temperature range, −40°C ≤ TJ ≤ 125°C, all other limits apply for TJ = 25°C.

LM2990-12 LM2990-15 Units

(Limit)

Parameter Conditions Typ Limit Typ Limit

(Note 4) (Note 5) (Note 4) (Note 5)

Output Voltage (VO)5 mA ≤ IO ≤ 1A

−12

−11.76

−15

−14.70 V (max)

−12.24 −15.30 V (min)

5 mA ≤ IO ≤ 1A −11.40 −14.25 V (max)

−12.60 −15.75 V (min)

Line Regulation IO = 5 mA, 6 60 6 60 mV (max)

VO(NOM) −1V > VIN > −26V

Load Regulation 50 mA ≤ IO ≤ 1A 3 50 3 50 mV (max)

Dropout Voltage IO = 0.1A, ΔVO ≤ 100 mV 0.1 0.3 0.1 0.3 V (max)

IO = 1A, ΔVO ≤ 100 mV 0.6 10.6 1V (max)

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LM2990

LM2990-12 LM2990-15 Units

(Limit)

Parameter Conditions Typ Limit Typ Limit

(Note 4) (Note 5) (Note 4) (Note 5)

Quiescent Current (Iq)IO ≤ 1A 1 5 1 5 mA (max)

IO = 1A, VIN = VO(NOM) 9 50 9 50 mA (max)

Short Circuit Current RL = 1Ω (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 Vripple = 1 Vrms,52 42 52 42 dB (min)

ƒripple = 1 kHz, IO = 5 mA

Output Noise Voltage 10 Hz–100 kHz, IO = 5 mA 500 1500 600 1800 μV (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

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 − TA)/θJA. If this dissipation is exceeded, the die temperature will rise above 125°C, and the LM2990 will eventually go into thermal shutdown at a TJ 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, θJA is 50°C/W; with 1 square inch of copper area, θJA is 37°C/W; and with 1.6 or more square inches of copper area,

θJA is 32°C/W.

Note 4: Typicals are at TJ = 25°C 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 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 (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 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 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 acceller-

ated 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 spec-

ified frequency range.

Quiescent Current: That part of the positive input current

that does not contribute to the positive load current. The reg-

ulator 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.

www.national.com 4

LM2990

Typical Performance Characteristics

Dropout Voltage

1080114

Normalized Output Voltage

1080115

LM2990-5.0 and LM2990-5.2

Quiescent Current

1080116

LM2990-12

Quiescent Current

1080117

LM2990-15

Quiescent Current

1080118

LM2990-5 and LM2990-5.2

Low Voltage Behavior

1080119

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LM2990

LM2990-5 and LM2990-5.2

Line Transient Response

1080120

LM2990-5 and LM2990-5.2

Load Transient Response

1080121

LM2990-12 and LM2990-15

Low Voltage Behavior

1080122

LM2990-12 and LM2990-15

Line Transient Response

1080123

LM2990-12 and LM2990-15

Load Transient Response

1080124

LM2990-5 and LM2990-5.2

Ripple Rejection

1080125

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LM2990

LM2990-5 and LM2990-5.2

Output Impedance

1080126

Maximum Output Current

1080127

LM2990-12 and LM2990-15

Ripple Rejection

1080128

LM2990-12 and LM2990-15

Output Impedance

1080129

Maximum Output Current

1080130

Maximum Power

Dissipation (TO-220)

1080131

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LM2990

Maximum Power Dissipation

(TO-263) (See (Note 3))

1080132

Typical Applications

Post Regulator for an Isolated Switching Power Supply

1080105

The LM2940 is a positive 1A low dropout regulator; refer to

its datasheet for further information.

Fixed Current Sink

1080107

Adjustable Current Sink

1080110

www.national.com 8

LM2990

Application Hints

EXTERNAL CAPACITORS

The LM2990 regulator requires an output capacitor to main-

tain stability. The capacitor must be at least 10 μF aluminum

electrolytic or 1 μF solid tantalum. The output capacitor's ESR

must be less than 10Ω, or the zero added to the regulator

frequency response by the ESR could reduce the phase mar-

gin, creating oscillations (refer to the graph on the right). An

input capacitor, of at least 1 μF solid tantalum or 10 μF alu-

minum electrolytic, is also needed if the regulator is situated

more than 6″ from the input power supply filter.

FORCING THE OUTPUT POSITIVE

Due to an internal clamp circuit, the LM2990 can withstand

positive voltages on its output. If the voltage source pulling

the output positive is DC, the current must be limited to 1.5A.

A current over 1.5A fed back into the LM2990 could damage

the device. The LM2990 output can also withstand fast posi-

tive voltage transients up to 26V, without any current limiting

of the source. However, if the transients have a duration of

over 1 ms, the output should be clamped with a Schottky

diode to ground.

Output Capacitor ESR

1080109

9 www.national.com

LM2990

Equivalent Schematic

1080108

www.national.com 10

LM2990

Physical Dimensions inches (millimeters) unless otherwise noted

TO-220 3–Lead Molded Package

Order Number LM2990T-5.0, LM2990T-5.2, LM2990T-12 or LM2990T-15

NS Package Number T03B

11 www.national.com

LM2990

TO-263 3-Lead Plastic Surface Mount Package

Order Number LM2990S-5.0, LM2990S-12 or LM2990S-15

NS Package Number TS3B

16–Lead Ceramic Dual–in–Line Package

LM2990J-5.0-QML (5962-9571101QEA), LM2990J-12-QML (5962-9571001QEA), or LM2990J-15-QML (5962-9570901QEA),

NS Package Number J16A

www.national.com 12

LM2990

16–Lead Ceramic Surface–Mount Package

LM2990WG5.0-QML (5962-9571101QXA)

NS Package Number WG16A

13 www.national.com

LM2990

Notes

LM2990 Negative Low Dropout Regulator

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