7.1 Overview

The BUF20800-Q1 programmable voltage reference allows fast, easy adjustment of 18 programmable reference outputs and two channels for V_COM adjustment, each with 10-bit resolution. It offers very simple, time-efficient adjustment of the gamma reference and V_COM voltages. The BUF20800-Q1 is programmed through a high-speed, standard, two-wire interface. The BUF20800-Q1 features a double-register structure for each DAC channel to simplify the implementation of dynamic gamma control. This structure allows pre-loading of register data and rapid updating of all channels simultaneously.

Buffers 1−9 are able to swing to within 200mV of the positive supply rail, and to within 0.6V of the negative supply rail. Buffers 10−18 are able to swing to within 0.8V of the positive supply rail and to within 200mV of the negative supply rail.

The BUF20800-Q1 can be powered using an analog supply voltage from 7V to 18V, and a digital supply from 2V to 5.5V. The digital supply must be applied prior to or simultaneously with the analog supply to avoid excessive current and power consumption; damage to the device may occur if it is left connected only to the analog supply for extended periods of time. Figure 7 shows the power supply timing requirements.

Figure 7. Power Supply Timing Requirements

Figure 14 shows the BUF20800-Q1 in a typical configuration. In this configuration, the BUF20800-Q1 device address is 74h. The output of each digital-to-analog converter (DAC) is immediately updated as soon as data are received in the corresponding register (LD = 0).

For maximum dynamic range, set V_REFH = V_S − 0.2 V and V_REFL = GND + 0.2 V.