SBOS571C August 2011 – August 2018 BUF20800-Q1
In addition to the VCOM outputs, the REFH and REFL OUT outputs can also be used as fixed gamma references. The output voltage will be set by the REFH and REFL input voltages, respectively. Therefore, REFH OUT should be used for the highest voltage gamma reference, and REFL OUT for the lowest voltage gamma reference. A 22-channel solution can be created by using all 18 outputs, the two VCOM outputs, and both REFH/L OUT outputs for gamma references—see Figure 15. However, the REFH and REFL OUT buffers were designed to only drive light loads on the order of 5−10mA. Driving capacitive loads is not recommended with these buffers. In addition, the REFH and REFL buffers must not be allowed to saturate from sourcing/sinking too much current from REFH OUT or REFL OUT. Saturation of the REFH and REFL buffers results in errors in the voltages of OUT1−18 and VCOM OUT1−2. The BUF01900 can be used to provide a programmable VCOM output.