DESCRIPTION
The UTC ESD protection for the VIDEO, DDC and SYNC lines is implemented with low-capacitance current steering diodes. Separate positive supply rails are provided for the VIDEO, DDC and SYNC channels to facilitate interfacing with low voltage video controller ICs to provide design flexibility in multi-supply-voltage environments. Two non-inverting drivers provide buffering for the HSYNC and VSYNC signals from the video controller IC (SYNC1, SYNC2). These buffers accept TTL input levels and convert them to CMOS output levels that swing between Ground and VCC_SYNC, which is typically 5V. Additionally, each driver has a series termination resistor (RT) connected to the SYNC_OUT pin, eliminating the external termination resistors typically required for the HSYNC and VSYNC lines of the video cable. Two N-channel MOSFETs provide the level shifting function required when the DDC controller is operated at a lower supply voltage than the monitor. The gate terminals for the MOSFETs (VCC_DDC) should be connected to the supply rail (typically 3.3V) that supplies power to the transceivers of the DDC controller.
Unisonic Technologies
