Active Matrix Graphic VFD CL Series Tubes

BD-Chip In Glass Displays w/Built-in Driver

Vfd

Active-Matrix VFD with Phosphor on Chip
Allows Static Graphic Display Mode

Chip lighting vacuum fluorescent displays (CL Series), developed by Ise Electronics Corp. is a blend of semiconductor technology and conventional VFD technology. The manufactures build a 16x16-dot phosphor matrix on top of a semiconductor chip that integrates memory functions and display driver circuits.

These chips are arranged in a single- or double- stage format, making it possible for highly precise graphic displays.

(Fig.1 to the right shows the dot structure of such chips.)

High precision means that complex characters appear vividly on the display. Also, the display uses a self-emitting design, so no back light-backlight is required.

New technology has given these displays the additional benefits of low voltage (12 to 18V), high brightness (3500cd/cm2 when VDD2=15V), long life (20,000 hours) and low noise.

There is another benefit. Blanking signals can control brightness. Thus, the most appropriate brightness for a given purpose can be obtained.

(Table 1 to the right shows the characteristics of the conventional model and the CLVFD.)

Fig.1 Dot Structure of CLVFD

Table 1 Comparison with small graphic VFD and CLVFD

Items for comparison	Conventional small size graphic VFD	CL VFD
Brightness	450cd/m2 or higher	3500cd/m2
Matrix size	To be determined by external size and number of leads	16x16 dot per chip There is no restriction in the horizontal direction, but the maximum chip number in the vertical direction is 2.
Life expectancy	10KHrs. or more	20KHrs. or more
Power consumption	2W/10cm2	0.8W/10cm2
Drive voltage	ebc(+Ek)=60V to 130V	VDD2=12V to 18V
Filament bias voltage(Ek)	Ek=7V to 20V	Ek=0 to 1V
Optimal controller	High speed CPU or advanced function ASIC	Controllable using generally available CPU
Mounted on display tube(Pin)	FPC or fine leads frames	2.0mm Pitch few lead pin
Applications	General message display Measurement control	Information equipment Industrial purpose Medical purpose
Drive system	Multiplex drive	Static drive
Grid structure	Thin-width wire grid	Single-piece honeycomb mesh

Anode Structure Completely Different

The basic structure of the new display device is the same as that of conventional VFDs. It consists of three electrodes - the cathode, grid and anode. However, the structure of the anode in the new tube is completely different from that in conventional tubes.

In conventional VFDs complex wiring, insulation and phosphor layers are fabricated directly on the glass plate no semiconductor devices are arranged internally and many lead wires are pulled out of the VFD (Fig. 2). With the new technology, semiconductor chips on which the phosphor matrixes are fabricated and arranged on the glass plate. The chips and outer leads are connected by wire bonding. This technology reduces the number of lead wires pulled out of the VFD (Fig. 3). Therefore, mounting this device on printed circuit boards is easy compared to mounting conventional graphic VFDs.

Fig.2 Construction of conventional graphic VFD

Fig.3 Construction of CLVFD

No Special Power Source Required

Since these graphic displays incorporate semiconductor driver ICs with embedded memory static display mode becomes available even for graphic display applications. Therefore, the grid and anode voltage can be set between 12 and 18V. Meaning no special power source is required. (Tables 2 and 3 show drive conditions and electric characteristics of P/N MW12832D.)

Table 2 Recommended operating conditions (P/N MW12832D)

Parameter	Symbol	MIN	TYP	MAX	Unit
Filament voltage	Ef	2.5	2.8	3.1	Vac
Grid voltage	Ec	-	15.0	16.5	V
Filament bias voltage	Ek	0.0	0.6	1.0	V
Logic supply voltage	VDD1	4.5	5.0	5.5	V
Display supply voltage	VDD2	10.0	15.0	17.0	V
Hi-level input voltage	VIH	3.7	-	VDD1	V
Low-level input voltage	VIL	-	0.6	-	V
Clock frequency	fCLK	-	-	4	MHz

Table 3 Electrical characteristics (Ta=25°C)

Parameter	Sumbol	Test conditions	MIN	TYP	MAX	Unit
Filament current	If	All segment OFF	83	92	101	mAac
Grid current	Ic	All segment ON	-	12.0	24.0	mA
Grid current	IDD1	fCLK=1.25MHz	-	30.0	45.0	mA
Display supply current	IDD2	All segment ON	-	14.0	28.0	mA
Luminance	L	Enable="High"	2000	3500	-	cd/cm2
Color of illumination	Blue-green					-

Conventional tubes require drivers and multifunctional controllers, but CLVFDs do not because they contain internal semiconductor chips. They can easily be controlled using a generally available CPU. (Fig.4 shows a block diagram of the display system. Fig. 5 shows a block diagram of the inside of a chip.) The interface adopts a synchronized serial format and consists of data clock, latch and enabling logic. (Fig. 6 shows a timing chart for these logic devices.)


Fig.4 Block diagram	Fig.5 Internal logic diagram of CL chip	Fig.6 Interface timing chart

Benefits of New Technology

The introduction of these technologies has produced a number of benefits. These benefits include lower noise, longer life, higher brightness, fewer soldering points on PCBs, improved mounting workability and stable operation under a wide range of operating temperatures.
Also, improved storage-temperature and humidty levels.

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