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PDF M5219B Data sheet ( Hoja de datos )
| Número de pieza | M5219B | |
| Descripción | Advanced LCD Controller/Driver Family | |
| Fabricantes | OKI | |
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Hay una vista previa y un enlace de descarga de M5219B (archivo pdf) en la parte inferior de esta página. Total 13 Páginas | ||
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INTRODUCTION
With the continuing demand for smaller and more efficient systems, designers are seeking new ways to reduce power
and increase integration. This paper describes how good use of OKI Semiconductor’s monolithic display drivers can
reduce power consumption and component count in systems that incorporate liquid crystal displays (LCDs). Infor-
mation in this paper is applicable both to small LCD panels (with a dozen or less segmented digits) and to large LCD
panels (such as used for laptop screens).
LCD elements are capacitive in nature and dissipate virtually no power, whether selected or deselected. When an
LCD element is selected, a voltage is applied across the liquid crystal that varies the element’s reflectivity. Removing
the voltage deselects the LCD element and returns the liquid crystal to its original state.
In general, an alternating-current (AC) source is required to illuminate the individual elements in an LCD panel. A
direct-current (DC) source is not suitable for driving an LCD panel because of electrolytic reactions in the LCD’s
liquid. Placing a potential difference across the liquid in an LCD panel causes ion migration, which gradually erodes
the anode terminal and causes destructive deposition on the cathode terminal. The electrolytic reaction could be
diminished by plating the electrodes with a non-reactive conductive element, such as gold, for example; however,
the high cost of gold and similar non-reactive elements makes this solution impractical for all but the most esoteric
applications.
A far simpler way to eliminate electrolytic corrosion is to use an AC source to drive the LCD panel, eliminating uni-
directional ion migration and the associated problems. AC configurations for driving LCDs fall in two main catego-
ries, which are:
• Static driver configurations
• Multiplexed driver configurations
The next two sections describe these two configurations. The third section in this application note addresses power-
related issues. This application note concludes with some complete circuit examples.
USING STATIC DRIVERS
In configurations using static drivers, a separate driver signal (SEG) provides an AC source for each element, and all
elements use a single shared common (COM) terminal.
LCD elements are often segments of an alphanumeric digit. In larger configurations, LCD elements are individual
dots that emulate the appearance of a CRT monitor. Static driver configurations are simple to use and are generally
suitable for LCDs with less than 80 segments.
OKI Semiconductor supplies a range of single-chip solutions for static LCD driver configurations, some of which
also include built-in RC oscillation circuits, in small-outline IC (SOIC) and plastic quad flat pack (PQFP) packages.
The table below lists the main characteristics of single-chip static LCD drivers from OKI Semiconductor.
LCD Drivers for Static Configurations
Part Number
MSM5219B
MSM5221
MSM5265
Segments
48
56
80
On-Chip Oscillator
√
X
√
Drive Voltage (VLCD)
4.0 - 7.0
3.0 - 7.0
3.0 - 6.0
Package
60-lead PQFP
80-lead PQFP
100-lead PQFP
Figure 1 below shows static driver connections to a single-digit, seven-segment alphanumeric display. Separate driv-
ers, SEG1 - SEG8, power each segment. All segments share a common ground connection, COM.
1 OKI SEMICONDUCTOR
1 page  
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SEG1
COMB
SEG2
SEG3
SEG4
COMA
Figure 6. A 1/2 Bias, 1/2 Duty Cycle, Type B Configuration
Figure 7 below shows the waveforms for the 1/2 bias, 1/2 duty cycle configuration shown in Figure 6 above.
COM1
VDD
VLC1, 2
VLC3
COM2
VDD
VLC1, 2
VLC3
SEGn
VDD
VLC1, 2
On Off On Off On Off On Off On Off On Off On
VLC3
VLCD
COM2 - SEGn
0
-VLCD
Note:When 1/2 duty is selected and 1/2 bias is used, perform the following:
When the code is -01, short VLC1 and VLC2 to supply the bias voltage.
When the code is -02 or -03, externally short VLC1 and VLC2.
Figure 7. Waveforms for 1/2 Bias, 1/2 Duty Cycle, Type B Configuration
Figure 8 illustrates a 1/3 bias, 1/3 duty cycle, Type B LCD network, suitable for connection to OKI’s MSM6606.
5 OKI SEMICONDUCTOR
5 Page 
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VDD VLC1 VLC2 VLC3
VDD VLC1 VLC2 VLC3
RLCD
RLCD
For 1/2 bias (when 1/2 duty is selected)
VREF
RLCD
RLCD
RLCD
For 1/3 bias (when 1/3 duty is selected)
VREF
Figure 13. Network for Active Bias Generation
No load current flows through the dividing resistors because of the high input impedance of the operational amplifi-
ers. A resistor value for R of 10 kΩ is suitable for the above circuit.
APPLICATION CIRCUITS
This application note concludes with two illustrative application circuits. The first, shown in Figure 14 below, uses
two MSM6660 LCD drivers to provide three bias signals and 124 segment drivers for a 1/3 bias, 1/3 duty cycle, Type
B LCD panel containing 372 dots.
BL
CK
DATA
CE1
CE2
LCD Panel
BL
CK
DATA
CE
SEG0 ~ SEG61
COM1
COM2
COM3
COMOUT
SYNC
SEL VLC1 VLC2 VLC3 OSC
RLCD
R0
RLCD
RLCD
C0
BL
CK
DATA
CE
SEG0 ~ SEG61
COM1
COM2
COM3
COMOUT
SYNC
SEL VLC1 VLC2 VLC3 OSC
Figure 14. Application Circuit Example Using MSM6660 LCD Drivers
In the example on the previous page, a microcontroller may be necessary to provide an appropriate interface to the
overall system. Figure 15 below depicts a more complex example that may not require an additional microcontroller.
11 OKI SEMICONDUCTOR
11 Page | ||
| Páginas | Total 13 Páginas | |
| PDF Descargar | [ Datasheet M5219B.PDF ] | |
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