14 Programmable Gamma Reference Buffers with Four Static References for TFT-LCD Displays

Programmable Gamma Buffer with Column Driver Protection

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The MAX9591 provides 14 programmable voltage references and four static voltage references for gamma correction in TFT-LCD displays. Two register banks are provided to store two sets of gamma reference values that are programmed into the banks through an I²C interface. The outputs can switch between gamma reference values in 0.5µs.

The 14 programmable reference voltages are divided evenly into seven upper and seven lower voltages for the upper and lower gamma curves of LCD column drivers.

Each gamma reference voltage has an 8-bit digital-to-analog converter (DAC) with an isolation buffer associated with it to ensure stable operation. Therefore, the reference voltages remain stable without synchronizing to the LCD horizontal timing. In addition, each buffer is able to provide a high current that further ensures a stable voltage when critical levels and patterns are displayed.

The reference voltages ramp up proportional to AVDD during startup and gamma buffers wake up in high impedance until all of the registers are written. This protects the LCD column drivers from high transient currents and reverse bias conditions.

The MAX9591 is available in a 38-pin TQFN package and is specified for operation over the -40°C to +85°C temperature range.
MAX9591: Typical Operating Circuit MAX9591: Typical Operating Circuit Enlarge+

Key Features

  • 20V (max) Operating Voltage
  • 14 Programmable Reference Voltages
  • Four Static Reference Voltages
  • Independent DACs
  • 8-Bit Resolution per Channel
  • Two Register Banks for Two Sets of Gamma Values
  • Fast Switching Between Gamma Values
  • Output Swing within 100mV of Rails
  • 400mA Peak Current on Reference Channels and DAC Channels 1, 7, 8, and 14
  • 200mA Peak Current on DAC Channels 2–6, 9–13
  • Startup Column Driver Protection


  • Industrial Reference Voltage Generators
  • TFT-LCD Displays
Product Reliability Reports: MAX9591.pdf 
Device   Fab Process   Technology   Sample size   Rejects   FIT at 25°C   FIT at 55°C   Material Composition  

Note : The failure rates are summarized by technology and mapped to the associated material part numbers. The failure rates are highly dependent on the number of units tested.

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