Date: 23/01/2012

VFD Controller/Driver ICs for your design

Vacuum Fluorescent Display (VFD) displays are used when the display need to be bright and withstand harsh weather in applications such as micorwave ovens. They work in wide range of temperature, particularly suitable for cold outdoor use. Some more examples of applications include POS (point of sales), ECR (Electronic Cash Registers), Set-top Boxes, audio equipment, Blu-Ray Disc Players and multi-media computers as well as a host of applications with message display requirements.

VFD displays need VFD controller and driver IC to interface them a processor or a microcontroller. The new ICs released for this application are HT16523 & HT16525 from Holtek. This series has an integrated 5x7 or 5x8 dot matrix character font memory (ROM), can program selected characters and show the corresponding character output on display panels using the internal controller and driver circuits. Holtek says using these devices can greatly eliminate programming complexity for character generation and also reduce the MCU loading.

The HT16523 and HT16525 both support a 3-line serial interface, with a logic voltage of 2.7V~5.5V. The HT16523 VFD high voltage is ?40V while the HT16525 high voltage is ?60V. The HT16523 can display up to 16 5x7 dot characters, while the HT16525 can display up to 24 5x8 dot characters. The two devices both support on-chip 248 character sets which include Arabic numbers, English lowercase letters, capital letters, punctuation marks, Japanese kana or European letters. If the integrated font set requires additions, there is also an eight character RAM for users to program. Additionally Holtek also accepts user-define character font sets.

The Holtek character type VFD Controller and Driver IC series includes the HT16528, HT16525, and HT16523. The HT16528 main focus is in character generation and multiple character displays, with a total of 2 rows and 5x8 dot x 24 characters The HT16523 and HT16525 are main directed at different panel varieties. The HT16523 and HT16525 not only support Alphanumeric and Symbolic display, but also provide two additional Segment pins for Icon and cursor display. A total of 32 Icons can be displayed for the HT16523 and 48 Icons for the HT16525. The two devices also provide two Multi-purpose output pins to control LEDs or other components.

The HT1652x are all supplied in LQFP package types.

If you wish look at other alternates in the market for this application, check the little older MAX6853/MAX6853 from Maxim, They can drive 5 x 7 matrix VFD displays up to 96 characters and controls industry-standard, shift-register, high-voltage grid/anode VFD tube drivers. The device supports display tubes using either one or two digits per grid, as well as universal displays.

The two wire interfaced MAX6853 includes an ASCII 104-character font, multiplex scan circuitry, and static RAM that stores digit, cursor, and annunciator data, as well as font data for 24 user-definable characters. The MAX6852 supports SPI interface.

Another Taiwanese semiconductor vendor Princeton Technology Corp also makes family of VFD controllers/drivers. One of the part from this vendor is PT6397. PT6397 can driver 32 segment/grid output and has on-chip control circuit and RTC circuit suitable for a STB application. Serial data is fed to PT6397 via a 4-wire serial interface or I2C bus. It is housed in a 52-pin LQFP package