Intersil unveils programmable gamma buffer for ADAS displays

Intersil has developed, what it says, is the lowest power 14-channel programmable gamma buffer for automotive TFT-LCD displays. The automotive-grade ISL76534 is capable of delivering accurate gamma calibration in order to ensure consistent brightness and colour matching of every LCD panel inside a vehicle.

The ISL76534 has been designed for next generation LCDs for infotainment displays, advanced driver assistance system (ADAS) smart mirrors and instrument cluster displays.

The device provide engineers with one Vcom and 14 gamma channels with 10-bit resolution for fine-tuning the gamma curve which, if not corrected often lead to LCDs appearing bleached out or too dark. The ISL76534 can be used to calibrate and then store the gamma curve, guaranteeing that each LCD powers up and displays images that are pleasing to the eye. The device’s internal EEPROM stores the factory-calibrated gamma and Vcom reference values, and enables significantly higher reliability by offering 10,000 write cycles and 20 years of data retention at 105°C.

The circuit architecture makes it easier to use, while 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 in a controlled fashion preventing any possibility of an LCD panel lock-up, adding another layer of reliability for ADAS and safety systems. In addition, a high 75 dB PSRR prevents power supply noise from reaching the gamma buffer outputs and becoming visible in the LCD panel.

Power consumption is just 56.6mW, which is considerably lower than many existing devices, while its low power dissipation also eliminates the need for heatsinks, prevents junction temperature overheating, and allows engineers to use lower cost LDOs instead of switching regulators.

Key features and specifications of ISL76534

  • I2C programmable, 15-channel reference voltage outputs
  • 14-channel gamma references, 10-bit resolution, buffered outputs with 60mA Iout and 5V/µs slew rate
  • 1-channel Vcom calibrator, 10-bit resolution, 100mA (max) Iout and 5V/µs slew rate
  • Analogue supply operating range from 6.3V to 19V
  • Digital supply operating range from 2.25V to 3.6V
  • Ultra-low power consumption of 56.6mW simplifies power supply and thermal design
  • Analogue AVDD max current of 2.5mA, amp AVDD max current of 1.2mA, and digital DVDD max current of 0.33mA
  • Typical quiescent current power of 12mW at 8V
  • High PSRR of 75dB typical at DC
  • EEPROM data retention of 20 years at +105°C for extreme robustness and reliability
  • EEPROM endurance of 10,000 write cycles
  • Over-temperature protection against excessive die temperature
  • EC-Q100 Grade-2 qualified for operation from -40°C to +105°C

Neil Tyler