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PDF LM340 Data sheet ( Hoja de datos )
| Número de pieza | LM340 | |
| Descripción | 3-Terminal Positive Regulators | |
| Fabricantes | National Semiconductor | |
| Logotipo |  |
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July 2006
LM340/LM78XX Series
3-Terminal Positive Regulators
General Description
The LM140/LM340A/LM340/LM78XXC monolithic
3-terminal positive voltage regulators employ internal
current-limiting, thermal shutdown and safe-area compensa-
tion, making them essentially indestructible. If adequate heat
sinking is provided, they can deliver over 1.0A output cur-
rent. They are intended as fixed voltage regulators in a wide
range of applications including local (on-card) regulation for
elimination of noise and distribution problems associated
with single-point regulation. In addition to use as fixed volt-
age regulators, these devices can be used with external
components to obtain adjustable output voltages and cur-
rents.
Considerable effort was expended to make the entire series
of regulators easy to use and minimize the number of exter-
nal components. It is not necessary to bypass the output,
although this does improve transient response. Input by-
passing is needed only if the regulator is located far from the
filter capacitor of the power supply.
The 5V, 12V, and 15V regulator options are available in the
steel TO-3 power package. The LM340A/LM340/LM78XXC
series is available in the TO-220 plastic power package, and
the LM340-5.0 is available in the SOT-223 package, as well
as the LM340-5.0 and LM340-12 in the surface-mount TO-
263 package.
Features
n Complete specifications at 1A load
n Output voltage tolerances of ±2% at Tj = 25˚C and ±4%
over the temperature range (LM340A)
n Line regulation of 0.01% of VOUT/V of ∆VIN at 1A load
(LM340A)
n Load regulation of 0.3% of VOUT/A (LM340A)
n Internal thermal overload protection
n Internal short-circuit current limit
n Output transistor safe area protection
n P+ Product Enhancement tested
Typical Applications
Fixed Output Regulator
Adjustable Output Regulator
00778101
*Required if the regulator is located far from the power supply filter.
**Although no output capacitor is needed for stability, it does help transient
response. (If needed, use 0.1 µF, ceramic disc).
VOUT = 5V + (5V/R1 + IQ) R2 5V/R1 > 3 IQ,
00778102
load regulation (Lr) ≈ [(R1 + R2)/R1] (Lr of LM340-5).
Current Regulator
Comparison between SOT-223 and D-Pak (TO-252)
Packages
00778103
∆IQ = 1.3 mA over line and load changes.
© 2006 National Semiconductor Corporation DS007781
Scale 1:1
00778138
www.national.com
1 page  
LM140 Electrical Characteristics (Note 4) (Continued)
−55˚C ≤ TJ ≤ +150˚C unless otherwise specified
Output Voltage
5V
Symbol
Input Voltage (unless otherwise noted)
10V
Parameter
Conditions
Min Typ Max
Ripple Rejection
IO ≤ 1A, TJ = 25˚C 68 80
or
f = 120 Hz
IO ≤ 500 mA,
−55˚C ≤ TJ ≤+150˚C
VMIN ≤ VIN ≤ VMAX
68
(8 ≤ VIN ≤ 18)
RO Dropout Voltage TJ = 25˚C, IO = 1A
Output Resistance f = 1 kHz
Short-Circuit
Current
TJ = 25˚C
Peak Output
Current
TJ = 25˚C
Average TC of
0˚C ≤ TJ ≤ +150˚C, IO = 5 mA
VOUT
VIN Input Voltage TJ = 25˚C, IO ≤ 1A
Required to
Maintain
Line Regulation
2.0
8
2.1
2.4
−0.6
7.5
12V 15V
19V 23V Units
Min Typ Max Min Typ Max
61 72
60 70
dB
61 60 dB
(15 ≤ VIN ≤ 25)
2.0
18
1.5
(18.5 ≤ VIN ≤
28.5)
2.0
19
1.2
V
V
mΩ
A
2.4 2.4 A
−1.5
−1.8 mV/˚C
14.6
17.7
V
LM340 Electrical Characteristics (Note 4)
0˚C ≤ TJ ≤ +125˚C unless otherwise specified
Output Voltage
5V 12V 15V
Symbol
Input Voltage (unless otherwise noted)
10V 19V 23V Units
Parameter
Conditions
Min Typ Max Min Typ Max Min Typ Max
VO
Output Voltage
TJ = 25˚C, 5 mA ≤ IO ≤ 1A
PD ≤ 15W, 5 mA ≤ IO ≤ 1A
VMIN ≤ VIN ≤ VMAX
4.8 5 5.2 11.5 12 12.5 14.4 15 15.6
4.75
5.25 11.4
12.6 14.25
15.75
(7.5 ≤ VIN ≤ 20)
(14.5 ≤ VIN ≤
27)
(17.5 ≤ VIN ≤ 30)
V
V
V
∆VO
Line Regulation
IO = 500 mA TJ = 25˚C
∆VIN
3 50
(7 ≤ VIN ≤ 25)
4 120
4 150
(14.5 ≤ VIN ≤ (17.5 ≤ VIN ≤ 30)
30)
mV
V
IO ≤ 1A
0˚C ≤ TJ ≤ +125˚C
∆VIN
TJ = 25˚C
∆VIN
50
(8 ≤ VIN ≤ 20)
50
(7.5 ≤ VIN ≤ 20)
120 150
(15 ≤ VIN ≤ 27) (18.5 ≤ VIN ≤ 30)
120 150
(14.6 ≤ VIN ≤ (17.7 ≤ VIN ≤ 30)
27)
mV
V
mV
V
0˚C ≤ TJ ≤ +125˚C
25 60
75 mV
∆VIN
(8 ≤ VIN ≤ 12) (16 ≤ VIN ≤ 22) (20 ≤ VIN ≤ 26) V
∆VO
Load Regulation
TJ = 25˚C 5 mA ≤ IO ≤ 1.5A
10 50
12 120
12 150 mV
250 mA ≤ IO ≤ 750 mA
25
60
75 mV
5 mA ≤ IO ≤ 1A, 0˚C ≤ TJ ≤
50 120 150 mV
+125˚C
IQ
Quiescent Current IO ≤ 1A
TJ = 25˚C
0˚C ≤ TJ ≤ +125˚C
∆IQ Quiescent Current 5 mA ≤ IO ≤ 1A
Change
TJ = 25˚C, IO ≤ 1A
8
8.5
0.5
1.0
8
8.5
0.5
1.0
8 mA
8.5 mA
0.5 mA
1.0 mA
5 www.national.com
5 Page 
Application Hints
The LM340/LM78XX series is designed with thermal protec-
tion, output short-circuit protection and output transistor safe
area protection. However, as with any IC regulator, it be-
comes necessary to take precautions to assure that the
regulator is not inadvertently damaged. The following de-
scribes possible misapplications and methods to prevent
damage to the regulator.
SHORTING THE REGULATOR INPUT
When using large capacitors at the output of these regula-
tors, a protection diode connected input to output (Figure 1)
may be required if the input is shorted to ground. Without the
protection diode, an input short will cause the input to rapidly
approach ground potential, while the output remains near
the initial VOUTbecause of the stored charge in the large
output capacitor. The capacitor will then discharge through a
large internal input to output diode and parasitic transistors.
If the energy released by the capacitor is large enough, this
diode, low current metal and the regulator will be destroyed.
The fast diode in Figure 1 will shunt most of the capacitors
discharge current around the regulator. Generally no protec-
tion diode is required for values of output capacitance ≤ 10
µF.
RAISING THE OUTPUT VOLTAGE ABOVE THE INPUT
VOLTAGE
Since the output of the device does not sink current, forcing
the output high can cause damage to internal low current
paths in a manner similar to that just described in the “Short-
ing the Regulator Input” section.
REGULATOR FLOATING GROUND (Figure 2)
When the ground pin alone becomes disconnected, the
output approaches the unregulated input, causing possible
damage to other circuits connected to VOUT. If ground is
reconnected with power “ON”, damage may also occur to the
regulator. This fault is most likely to occur when plugging in
regulators or modules with on card regulators into powered
up sockets. Power should be turned off first, thermal limit
ceases operating, or ground should be connected first if
power must be left on.
TRANSIENT VOLTAGES
If transients exceed the maximum rated input voltage of the
device, or reach more than 0.8V below ground and have
sufficient energy, they will damage the regulator. The solu-
tion is to use a large input capacitor, a series input break-
down diode, a choke, a transient suppressor or a combina-
tion of these.
FIGURE 1. Input Short
00778108
00778109
FIGURE 2. Regulator Floating Ground
00778110
FIGURE 3. Transients
When a value for θ(H–A) is found using the equation shown,
a heatsink must be selected that has a value that is less than
or equal to this number.
θ(H–A) is specified numerically by the heatsink manufacturer
in this catalog, or shown in a curve that plots temperature
rise vs power dissipation for the heatsink.
11 www.national.com
11 Page | ||
| Páginas | Total 17 Páginas | |
| PDF Descargar | [ Datasheet LM340.PDF ] | |
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