Programmable buffer delivers gamma calibration accuracy for ADAS

Claimed to be the industry’s lowest power 14-channel programmable gamma buffer, the automotive-grade ISL76534 can be used in LCDs for infotainment displays, ADAS smart mirrors and instrument cluster displays. According to Intersil, it delivers the highest accuracy gamma calibration to ensure consistent brightness and colour matching of every LCD panel inside a vehicle.

It provides engineers with one Vcom and 14 gamma channels with 10bit resolution for fine-tuning the gamma curve. (LCD panels that are not properly gamma corrected can appear bleached out, or too dark.) It can calibrate and store the gamma curve, guaranteeing that each LCD powers up and displays clear images.

The internal EEPROM stores the factory-calibrated gamma and Vcom reference values. It is claimed to enable significantly higher reliability than competitive devices by offering 10,000 write cycles and 20 years of data retention at 105°C.

The circuit architecture means that no power-supply sequencing is required; either analogue or digital power supplies can start up first. At initialisation, all gamma buffer and Vcom output channels monotonically start up together, preventing any possibility of an LCD panel lock-up. This adds another layer of reliability for ADAS and safety systems, says the company, such as back-up cameras that rely on LCD panels to start up immediately and operate. The high 75dB PSRR prevents power supply noise from reaching the gamma buffer outputs and becoming visible in the LCD panel.

The power consumption of 56.6mW is five times lower than the closest competitor, claims the company. Typical quiescent current power is 12mW at 8V. The low maximum output current for analogue, digital, and Vcom supplies simplifies power supply and thermal design. The low power dissipation also eliminates the need for heatsinks, prevents junction temperature overheating, and allows the use of LDOs instead of switching regulators, to save costs.

Analogue supply operating range is 6.3 to 19V and the digital supply operating range is from 2.25 to 3.6V. Analogue AVDD maximum current is 2.5mA, with an AVDD maximum current of 1.2mA, and digital DVDD max current of 0.33mA.

Supplied in a compact 4.5 x 5.0mm, 28-lead TQFN package, the AEC-Q100 Grade-2 device is qualified for operation from -40 to +105°C.


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