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PDF LM2940 Data sheet ( Hoja de datos )
| Número de pieza | LM2940 | |
| Descripción | 1-A LOW-DROPOUT VOLTAGE REGULATOR | |
| Fabricantes | Texas | |
| Logotipo |  |
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FEATURES
• Dropout Voltage 0.385 V (Typ) at IO = 1 A
• Output Current in Excess of 1 A
• Output Voltage Trimmed Before Assembly
• Reverse-Battery Protection
• Internal Short-Circuit Current Limit
• Mirror-Image Insertion Protection
• Available in
– Commercial Temperature (0°C to 125°C)
– Extended Temperature (–40°C to 125°C)
DESCRIPTION/ORDERING
INFORMATION
The LM2940 positive-voltage regulator features the
ability to source 1 A of output current, with a typical
dropout voltage of 0.385 V and a maximum of
800 mV over the entire temperature range.
Furthermore, a quiescent current reduction circuit
has been included, which reduces the ground current
when the differential between the input voltage and
the output voltage exceeds approximately 3 V. The
quiescent current with 1 A of output current and an
input-output differential of 5 V is, therefore, only
30 mA. Higher quiescent currents only exist when
the regulator is in the dropout mode (VI – VO ≤ 3 V).
Also designed for vehicular applications, the LM2940
and all regulated circuitry are protected from reverse
battery installations or two-battery jumps. During line
transients, such as load dump when the input
voltage can momentarily exceed the specified
maximum operating voltage, the regulator
automatically shuts down to protect both the internal
circuits and the load. The LM2940 is not harmed by
temporary mirror-image insertion. Familiar regulator
features, such as short-circuit and thermal-overload
protection, also are provided.
LM2940
1-A LOW-DROPOUT VOLTAGE REGULATOR
SLVS634 – MAY 2006
DCY (SOT-223) PACKAGE
(TOP VIEW)
GND
1 23
KTT (TO-263) PACKAGE
(TOP VIEW)
3 OUT
2 GND
1 IN
KCS (TO-220) PACKAGE
(TOP VIEW)
GND
OUT
GND
IN
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas
Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2006, Texas Instruments Incorporated
1 page  
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LM2940
1-A LOW-DROPOUT VOLTAGE REGULATOR
SLVS634 – MAY 2006
LM2940x Electrical Characteristics
VI = VO + 5 V, IO = 1 A, CO = 22 µF (unless otherwise noted)
PARAMETER
TEST CONDITIONS
VO Output voltage
Line regulation
Load regulation
ZO Output impedance
IQ Quiescent current
Vn Output noise voltage
Ripple rejection
Long-term stability
5 mA ≤ IO ≤ 1 A,
9 V: 10.5 V ≤ VI ≤ 26 V,
12 V: 13.6 V ≤ VI ≤ 26 V
VO + 2 V ≤ VI ≤ 26 V, IO = 5 mA
50 mA ≤ IO ≤ 1 A
LM2940I
LM2940C
100 mAdc, 20 mArms, fO = 120 Hz
VO + 2 V ≤ VI ≤ 26 V,
IO = 5 mA
LM2940I
LM2940C
VI = VO + 5 V, IO = 1 A
fO = 10 Hz to 100 kHz, IO = 5 mA
fO = 120 Hz, 1 Vrms,
IO = 100 mA
LM2940I
LM2940C
VI – VO Dropout voltage
IO(MAX) Short-circuit current
Maximum line transient
Reverse polarity
dc input voltage
IO = 1 A
IO = 100 mA
RO = 100 Ω, t ≤ 100 ms
RO = 100 Ω, t ≤ 1 ms
RO = 100 Ω
Reverse polarity transient input
voltage
RO = 100 Ω, t ≤ 100 ms
RO = 100 Ω, t ≤ 1 ms
LM2940I
LM2940C
LM2940I
LM2940C
LM2940I
LM2940C
TA (1)
25°C
Full range
25°C
25°C
Full range
25°C
25°C
25°C
Full range
25°C
25°C
Full range
25°C
25°C
Full range
25°C
25°C
25°C
Full range
25°C
Full range
25°C
25°C
Full range
25°C
25°C
Full range
25°C
25°C
Full range
25°C
Full range
MIN
11.64
12 V
TYP
12
11.4
MAX
12.36
12.6
UNIT
V
20 120 mV
55 120
200 mV
55 120
80 mΩ
10 15
20
10 15 mA
30 45
60
360
54 66
µVrms
48 dB
54 66
48
mV/
1000 h
400 500
800
mV
110 150
200
1.6 1.9
A
60 75
60 V
45 55
–15 –30
–15 V
–15 –30
–50 –75
–50
–45 –55
V
–45
(1) Full range TA is –40°C to 125°C for the LM2940I and 0°C to 125°C for the LM2940C.
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LM2940
1-A LOW-DROPOUT VOLTAGE REGULATOR
SLVS634 – MAY 2006
Heatsinking
APPLICATION INFORMATION (continued)
A heatsink may be required, depending on the maximum power dissipation and maximum ambient temperature
of the application. Under all possible operating conditions, the junction temperature must be within the range
specified under absolute maximum ratings.
To determine if a heatsink is required, the power dissipated by the regulator, PD, must be calculated.
Figure 3 shows the voltages and currents that are present in the circuit, as well as the formula for calculating the
power dissipated in the regulator.
IIN
VIN
IN OUT
VOUT
IL
GND
LOAD
IG
II = IL + IG
PD = (VIN – VOUT)IL + (VIN)IG
Figure 3. Power Dissipation
The next parameter that must be calculated is the maximum allowable temperature rise, TR(max). This is
calculated using the formula:
TR(max) = TJ(max) – TA(max)
Where
TJ(max) is the maximum allowable junction temperature, which is 125°C for commercial parts.
TA(max) is the maximum ambient temperature encountered in the application.
Using the calculated valued for TR(max) and PD, the maximum allowable value for the junction-to-ambient
thermal resistance, θJA, now can be found:
θJA = TR(max) ÷ PD
NOTE:
If the maximum allowable value for θJA is found to be ≥53°C/W for the TO-220
package, ≥80°C/W for the TO-263 package, or ≥174°C/W for the SOT-223 package,
no heatsink is needed, because the package alone dissipates enough heat to satisfy
these requirements.
If the calculated value for θJA falls below these limits, a heatsink is required.
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| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet LM2940.PDF ] | |
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