|
|
PDF LM3915 Data sheet ( Hoja de datos )
| Número de pieza | LM3915 | |
| Descripción | Dot/Bar Display Driver | |
| Fabricantes | National Semiconductor | |
| Logotipo |  |
|
Hay una vista previa y un enlace de descarga de LM3915 (archivo pdf) en la parte inferior de esta página. Total 24 Páginas | ||
|
No Preview Available !
January 2000
LM3915
Dot/Bar Display Driver
General Description
The LM3915 is a monolithic integrated circuit that senses
analog voltage levels and drives ten LEDs, LCDs or vacuum
fluorescent displays, providing a logarithmic 3 dB/step ana-
log display. One pin changes the display from a bar graph to
a moving dot display. LED current drive is regulated and pro-
grammable, eliminating the need for current limiting resis-
tors. The whole display system can operate from a single
supply as low as 3V or as high as 25V.
The IC contains an adjustable voltage reference and an ac-
curate ten-step voltage divider. The high-impedance input
buffer accepts signals down to ground and up to within 1.5V
of the positive supply. Further, it needs no protection against
inputs of ±35V. The input buffer drives 10 individual com-
parators referenced to the precision divider. Accuracy is typi-
cally better than 1 dB.
The LM3915’s 3 dB/step display is suited for signals with
wide dynamic range, such as audio level, power, light inten-
sity or vibration. Audio applications include average or peak
level indicators, power meters and RF signal strength
meters. Replacing conventional meters with an LED bar
graph results in a faster responding, more rugged display
with high visibility that retains the ease of interpretation of an
analog display.
The LM3915 is extremely easy to apply. A 1.2V full-scale
meter requires only one resistor in addition to the ten LEDs.
One more resistor programs the full-scale anywhere from
1.2V to 12V independent of supply voltage. LED brightness
is easily controlled with a single pot.
The LM3915 is very versatile. The outputs can drive LCDs,
vacuum fluorescents and incandescent bulbs as well as
LEDs of any color. Multiple devices can be cascaded for a
dot or bar mode display with a range of 60 or 90 dB.
LM3915s can also be cascaded with LM3914s for a linear/
log display or with LM3916s for an extended-range VU
meter.
Features
n 3 dB/step, 30 dB range
n Drives LEDs, LCDs, or vacuum fluorescents
n Bar or dot display mode externally selectable by user
n Expandable to displays of 90 dB
n Internal voltage reference from 1.2V to 12V
n Operates with single supply of 3V to 25V
n Inputs operate down to ground
n Output current programmable from 1 mA to 30 mA
n Input withstands ±35V without damage or false outputs
n Outputs are current regulated, open collectors
n Directly drives TTL or CMOS
n The internal 10-step divider is floating and can be
referenced to a wide range of voltages
The LM3915 is rated for operation from 0˚C to +70˚C. The
LM3915N-1 is available in an 18-lead molded DIP package.
© 2000 National Semiconductor Corporation DS005104
www.national.com
1 page  
Typical Performance Characteristics (Continued)
Input Current Beyond
Signal Range (Pin 5)
LED Current vs
Reference Loading
LED Driver Current
Regulation
DS005104-40
DS005104-41
Total Divider Resistance
vs Temperature
Common-Mode Limits
Output Characteristics
DS005104-42
DS005104-43
DS005104-44
DS005104-45
5 www.national.com
5 Page 
Application Hints (Continued)
FIGURE 5. Low Cost Circuit for 60 dB Display
DS005104-13
FIGURE 6. Improved Circuit for 60 dB Display
DS005104-14
To extend this approach to get a 90 dB display, another
30 dB of amplification must be placed in the signal path
ahead of the lowest LM3915. Extreme care is required as the
lowest LM3915 displays input signals down to 0.5 mV! Sev-
eral offset nulls may be required. High currents should not
share the same path as the low level signal. Also power line
wiring should be kept away from signal lines.
450 µA to flow from pin 7 into the divider which means that
the LED current will be at least 5 mA. R1 will typically be be-
tween 1 kΩ and 2 kΩ. To trim the reference voltage, vary R2.
The circuit in Figure 8 shows how to add a LED intensity con-
trol which can vary LED current from 9 mA to 28 mA. The ref-
erence adjustment has some effect on LED intensity but the
reverse is not true.
TIPS ON REFERENCE VOLTAGE
AND LED CURRENT PROGRAMMING
SINGLE LM3915
The equations in Figure 7 illustrate how to choose resistor
values to set reference voltage for the simple case where no
LED intensity adjustment is required. A LED current of 10 mA
to 20 mA generally produces adequate illumination. Having
10V full-scale across the internal voltage divider gives best
accuracy by keeping signal level high relative to the offset
voltage of the internal comparators. However, this causes
MULTIPLE LM3915s
Figure 9 shows how to obtain a common reference trim and
intensity control for two LM3915s. The two ICs may be con-
nected in cascade for a 60 dB display or may be handling
separate channels for stereo. This technique can be ex-
tended for larger numbers of LM3915s by varying the values
of R1, R2 and R3 in inverse proportion to the number of de-
vices tied in. The ICs’ internal references track within
100 mV so that worst case error from chip to chip is only
0.1 dB for VREF = 10V.
11 www.national.com
11 Page | ||
| Páginas | Total 24 Páginas | |
| PDF Descargar | [ Datasheet LM3915.PDF ] | |
Hoja de datos destacado
| Número de pieza | Descripción | Fabricantes |
| LM391 | LM391 Audio Power Driver | National Semiconductor |
| LM391 | LM391 Audio Power Driver (Rev. A) |  Texas Instruments |
| LM39100 | 1A Low-Voltage Low-Dropout Regulator |  HTC |
| LM39101 | 1A Low-Voltage Low-Dropout Regulator | HTC |
| Número de pieza | Descripción | Fabricantes |
| SLA6805M | High Voltage 3 phase Motor Driver IC. |
 Sanken |
| SDC1742 | 12- and 14-Bit Hybrid Synchro / Resolver-to-Digital Converters. |
 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, |
| DataSheet.es | 2020 | Privacy Policy | Contacto | Buscar |