DataSheet.es    


PDF LM117H Data sheet ( Hoja de datos )

Número de pieza LM117H
Descripción POSITIVE THREE TERMINAL ADJUSTABLE VOLTAGE REGULATOR
Fabricantes National Semiconductor 
Logotipo National Semiconductor Logotipo



Hay una vista previa y un enlace de descarga de LM117H (archivo pdf) en la parte inferior de esta página.


Total 26 Páginas

No Preview Available ! LM117H Hoja de datos, Descripción, Manual

August 1999
LM117/LM317A/LM317
3-Terminal Adjustable Regulator
General Description
The LM117 series of adjustable 3-terminal positive voltage
regulators is capable of supplying in excess of 1.5A over a
1.2V to 37V output range. They are exceptionally easy to
use and require only two external resistors to set the output
voltage. Further, both line and load regulation are better than
standard fixed regulators. Also, the LM117 is packaged in
standard transistor packages which are easily mounted and
handled.
In addition to higher performance than fixed regulators, the
LM117 series offers full overload protection available only in
IC’s. Included on the chip are current limit, thermal overload
protection and safe area protection. All overload protection
circuitry remains fully functional even if the adjustment termi-
nal is disconnected.
Normally, no capacitors are needed unless the device is situ-
ated more than 6 inches from the input filter capacitors in
which case an input bypass is needed. An optional output
capacitor can be added to improve transient response. The
adjustment terminal can be bypassed to achieve very high
ripple rejection ratios which are difficult to achieve with stan-
dard 3-terminal regulators.
Besides replacing fixed regulators, the LM117 is useful in a
wide variety of other applications. Since the regulator is
“floating” and sees only the input-to-output differential volt-
age, supplies of several hundred volts can be regulated as
long as the maximum input to output differential is not ex-
ceeded, i.e., avoid short-circuiting the output.
Also, it makes an especially simple adjustable switching
regulator, a programmable output regulator, or by connecting
a fixed resistor between the adjustment pin and output, the
LM117 can be used as a precision current regulator. Sup-
plies with electronic shutdown can be achieved by clamping
the adjustment terminal to ground which programs the out-
put to 1.2V where most loads draw little current.
For applications requiring greater output current, see LM150
series (3A) and LM138 series (5A) data sheets. For the
negative complement, see LM137 series data sheet.
Features
n Guaranteed 1% output voltage tolerance (LM317A)
n Guaranteed max. 0.01%/V line regulation (LM317A)
n Guaranteed max. 0.3% load regulation (LM117)
n Guaranteed 1.5A output current
n Adjustable output down to 1.2V
n Current limit constant with temperature
n P+ Product Enhancement tested
n 80 dB ripple rejection
n Output is short-circuit protected
Typical Applications
1.2V–25V Adjustable Regulator
DS009063-1
Full output current not available at high input-output voltages
*Needed if device is more than 6 inches from filter capacitors.
Optional — improves transient response. Output capacitors in the range
of 1 µF to 1000 µF of aluminum or tantalum electrolytic are commonly
used to provide improved output impedance and rejection of transients.
LM117 Series Packages
Part Number
Suffix
K
H
T
E
S
EMP
MDT
Package
TO-3
TO-39
TO-220
LCC
TO-263
SOT-223
TO-252
Design
Load
Current
1.5A
0.5A
1.5A
0.5A
1.5A
1A
0.5A
SOT-223 vs D-Pak (TO-252)
Packages
© 1999 National Semiconductor Corporation DS009063
Scale 1:1
DS009063-54
www.national.com

1 page




LM117H pdf
Application Hints
In operation, the LM117 develops a nominal 1.25V reference
voltage, VREF, between the output and adjustment terminal.
The reference voltage is impressed across program resistor
R1 and, since the voltage is constant, a constant current I1
then flows through the output set resistor R2, giving an out-
put voltage of
aluminum electrolytic) on the output swamps this effect and
insures stability. Any increase of the load capacitance larger
than 10 µF will merely improve the loop stability and output
impedance.
Load Regulation
The LM117 is capable of providing extremely good load
regulation but a few precautions are needed to obtain maxi-
mum performance. The current set resistor connected be-
tween the adjustment terminal and the output terminal (usu-
ally 240) should be tied directly to the output (case) of the
regulator rather than near the load. This eliminates line
drops from appearing effectively in series with the reference
and degrading regulation. For example, a 15V regulator with
0.05resistance between the regulator and load will have a
load regulation due to line resistance of 0.05x IL. If the set
resistor is connected near the load the effective line resis-
tance will be 0.05(1 + R2/R1) or in this case, 11.5 times
worse.
Figure 2 shows the effect of resistance between the regula-
tor and 240set resistor.
FIGURE 1.
DS009063-5
Since the 100 µA current from the adjustment terminal repre-
sents an error term, the LM117 was designed to minimize
IADJ and make it very constant with line and load changes.
To do this, all quiescent operating current is returned to the
output establishing a minimum load current requirement. If
there is insufficient load on the output, the output will rise.
External Capacitors
An input bypass capacitor is recommended. A 0.1 µF disc or
1 µF solid tantalum on the input is suitable input bypassing
for almost all applications. The device is more sensitive to
the absence of input bypassing when adjustment or output
capacitors are used but the above values will eliminate the
possibility of problems.
The adjustment terminal can be bypassed to ground on the
LM117 to improve ripple rejection. This bypass capacitor
prevents ripple from being amplified as the output voltage is
increased. With a 10 µF bypass capacitor 80 dB ripple rejec-
tion is obtainable at any output level. Increases over 10 µF
do not appreciably improve the ripple rejection at frequen-
cies above 120 Hz. If the bypass capacitor is used, it is
sometimes necessary to include protection diodes to prevent
the capacitor from discharging through internal low current
paths and damaging the device.
In general, the best type of capacitors to use is solid tanta-
lum. Solid tantalum capacitors have low impedance even at
high frequencies. Depending upon capacitor construction, it
takes about 25 µF in aluminum electrolytic to equal 1 µF
solid tantalum at high frequencies. Ceramic capacitors are
also good at high frequencies; but some types have a large
decrease in capacitance at frequencies around 0.5 MHz. For
this reason, 0.01 µF disc may seem to work better than a 0.1
µF disc as a bypass.
Although the LM117 is stable with no output capacitors, like
any feedback circuit, certain values of external capacitance
can cause excessive ringing. This occurs with values be-
tween 500 pF and 5000 pF. A 1 µF solid tantalum (or 25 µF
DS009063-6
FIGURE 2. Regulator with Line Resistance in Output
Lead
With the TO-3 package, it is easy to minimize the resistance
from the case to the set resistor, by using two separate leads
to the case. However, with the TO-39 package, care should
be taken to minimize the wire length of the output lead. The
ground of R2 can be returned near the ground of the load to
provide remote ground sensing and improve load regulation.
Protection Diodes
When external capacitors are used with any IC regulator it is
sometimes necessary to add protection diodes to prevent
the capacitors from discharging through low current points
into the regulator. Most 10 µF capacitors have low enough
internal series resistance to deliver 20A spikes when
shorted. Although the surge is short, there is enough energy
to damage parts of the IC.
When an output capacitor is connected to a regulator and
the input is shorted, the output capacitor will discharge into
the output of the regulator. The discharge current depends
on the value of the capacitor, the output voltage of the regu-
lator, and the rate of decrease of VIN. In the LM117, this dis-
charge path is through a large junction that is able to sustain
15A surge with no problem. This is not true of other types of
positive regulators. For output capacitors of 25 µF or less,
there is no need to use diodes.
The bypass capacitor on the adjustment terminal can dis-
charge through a low current junction. Discharge occurs
when either the input or output is shorted. Internal to the
LM117 is a 50resistor which limits the peak discharge cur-
rent. No protection is needed for output voltages of 25V or
5 www.national.com

5 Page





LM117H arduino
Schematic Diagram
Typical Applications
5V Logic Regulator with Electronic Shutdown*
Slow Turn-On 15V Regulator
DS009063-8
*Min. output ) 1.2V
DS009063-3
DS009063-9
11 www.national.com

11 Page







PáginasTotal 26 Páginas
PDF Descargar[ Datasheet LM117H.PDF ]




Hoja de datos destacado

Número de piezaDescripciónFabricantes
LM1173-Terminal Adjustable RegulatorNational Semiconductor
National Semiconductor
LM1171.2V TO 37V VOLTAGE REGULATORSTMicroelectronics
STMicroelectronics
LM1171.5 AMP POSITIVE ADJUSTABLE VOLTAGE REGULATOR FOR HI-REL APPLICATIONSSeme LAB
Seme LAB
LM117LM117 LM317-N Wide Temperature Three-Pin Adjustable Regulator (Rev. P)Texas Instruments
Texas Instruments

Número de piezaDescripciónFabricantes
SLA6805M

High Voltage 3 phase Motor Driver IC.

Sanken
Sanken
SDC1742

12- and 14-Bit Hybrid Synchro / Resolver-to-Digital Converters.

Analog Devices
Analog Devices


DataSheet.es es una pagina web que funciona como un repositorio de manuales o hoja de datos de muchos de los productos más populares,
permitiéndote verlos en linea o descargarlos en PDF.


DataSheet.es    |   2020   |  Privacy Policy  |  Contacto  |  Buscar