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The NEW CIG-VFD BD Series Built-in Drivers
LATEST DRIVER MOUNTING STRUCTURE CHARGES CIG TECHNIQUES
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 Vacuum fluorescent display (VFD), which find widespread use as easy-to-see display elements, now face new technical demands for improvement. Developers must shrink the size and weight again, further lower the energy consumption, extend the service life and enhance luminosity to accommodate the diversity of new electric devices.
Aiming to meet these demands, Ise Electronics Corp. has developed the BD series of chip-in-glass (CIG) vacuum fluorescent displays (VFDs). Despite their use of CIG formats, the models in the BD series feature package sizes equivalent to those of conventional VFDs. In short, the engineers produced an even more compact display module than before, because the BD series does not require chip-mounting space, an indispensable aspect of conventional CIGs. Incorporating dense drivers, the BD series also expands the possibility of using static drivers to display patterns ... patterns ... a difficult task for conventional VFDs.
Basic Structure
 The BD series incorporates slim, dense drivers inside the VFD. Conventional CIG devices require extra space for mounting drivers. As a result, the VFDs main unit has larger external dimensions than regular VFDs. To solve this, Noritake developed a slim driver chip just for the BD series, allowing the driver to install under a frame supporting the filament. This technique makes the CIGs more compact than conventional CIGs.
The BD series VFDs are equal in size or smaller than conventional VFDs with no chip mounting. However, the read-pin total restricts the compactness of conventional VFDs. In contrast, the BD series uses fewer lead pins than conventional models, and therefore can be smaller (Photo 1 and Table 1). To construct the display, engineers affix the built-in driver to the glass substrate under the metallic frame (Fig.1), which supports the filament. Wire bonding connects it to the pad that attaches to the glass plate. In operation, input signals for the driver and the power supply transmit outside the VFD through the wiring on the glass plate. Outputs from the drivers travels to each segment or grid through conductor traces on the glass plate as well (Fig.1).
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Tabel 1 Comparison of Conventional VFD and BD Series VFD
| Item |
Conventional VFD |
BDVFD |
| Part Number |
MH12816A |
MN12818A |
| Number of dots |
128x16 |
128x18 |
| Outer Dimension(PLxPHxPT) |
110x24x6.6mm |
110x25x6.6mm |
| Number of lead pins |
142 |
15 |
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Built-in Driver
Depending on the uses and display patterns, the BD series of VFDs incorporates one to four slim driver chips, each offering 96 or 128 bits and strong voltage-output ports. The driver incorporates a level shifter (Fig.2), consisting of CMOS field effect transistors (FETs), a latch, and shift register circuits. This is consistent with conventional VFD drivers.
Additionally, the driver incorporates a general synchronous serial-data input for the interface. When installing multiple drivers, it is most common to use serial connections between the drivers. |
Static Drive
 It is difficult for conventional VFDs to use static drivers to display complex patterns having relatively numerous segments, because of the need to raise the lead pin total. Since it allows installation of several dense drivers, the BD series permits use of static drives even for complex display patterns.
For instance, the models installed with a 96-bit driver in a two-chip series (Fig.3), each driver output in the static drive connects to every segment (anode) of the display patterns. The power supply normally transmits the grid voltage without passing it through the driver. Unlike dynamic drives, static drives face the disadvantage of having to increase the driver chip number in step with the rising segment count. However, since pattern division by grid is not necessary, the static drive offers an advantage by placing fewer restrictions on the pattern shape or position. This advantage becomes apparent in systems that emphasize design, such as displaying patterns having custom designs.
Additionally, static drives operate at low voltages, down to 10V. Static drives may yield lower power consumption, longer product life, and less noise than dynamic drives, when displaying the same kinds of patterns. Unlike dynamic drivers, static drives allow operation without exhibiting blurring by grid scans. Engineers can easily raise luminance by increasing the voltage. |
Multiplex Drive
 Engineers prefer multiplex (dynamic) drives in systems that display text in 5 x 7 dot matrix. Static drives are difficult to use when these image displays require a large segment total.
In multiplex drives, the driver output connects to the grid as well as to the anode. There are two kinds of systems, depending on the uses and display patterns. One system combines the anode (segment) and the grid scan data in single driver. The other system uses separate drivers for the grid and anode data. When using a single chip driver for the grid and the anode (Fig.4), the grid scan and the anode data must combine in the software and undergo input as data. Such arrangements contribute heavily to shrinking the size and cost of the entire system, because they help diminish the construction and mounting costs of the VFD driver circuit. |
The logic device in the driver requires several components. These include a filament power supply (just as in regular VFDs), a +5V power supply, and a display power supply. Every model of the BD series adopts uniform pin connection styles, including power supply terminals (Table 2). The interface features C-MOS level synchronous serial data input. This enables direct control from general purpose, low-end microprocessors.
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Table 2 Power Supply
| Terminal |
Function |
| F1/F2 |
Filament Voltage(AC) |
| VDD1 |
Logic Power Supply(5V) |
| VDD2 |
Display Power Supply |
| G |
Grid Voltage (Static Drive Only) |
| Vss |
Ground |
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Table 3 Interface Function
| Terminal |
Function |
| CLK |
Clock for Shift Register |
| SI |
Serial Data Input |
| SO |
Serial Data Output for Grid Scan Watching |
| LAT |
Latch Control(H=through, L=latch) |
| BK |
Driver Output Blanking |
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Capability for Full Dot-matrix Displays
The combination of the technology in the BD series, and thin-film, fine wiring techniques makes it possible for the series to serve in graphic displays. If engineers use CIG formats to design a graphic VFD, they can substantially cut down on the number of lead pins. VFD mounting then becomes extraordinarily easy. Additionally, technology in the BD series assures low voltage driving, low energy consumption, and improved luminance. Ise Electronics Corp. is planning to expand the BD series for several kinds of standard full-matrix displays.
Technology to Solve Problems
The chief feature of CIG designs is the elimination of special, external drivers for the VFD. The BD series also offers optimum advantages from compact chip designs, and from the use of the static drive, which alone offers several benefits.
In recent years, portable electronics have found widespread acceptance among consumers. The CIG technology within the BD series will offer solutions to challenges for miniature designs. This includes efforts to shrink the drive circuit, a primary goal for engineers seeking to attain compact products that consume little energy. The technology in the BD series also highlights a direction for VFD developers seeking to crate flat panel displays. |
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