NXP HDMI Companion Chip for Mobile Devices, Providing Level Shifting for DDC, CEC and HPD

“Smartphones, smartbooks and netbooks are among the first mobile applications using HDMI connectivity. Due to their compactness, rich feature set and need to save both board space and energy to increase battery life, our first customers have selected the IP4791CZ12 for these applications to achieve a stable HDMI interface design which is robust against ESD strikes and EMI distortion. They benefit from direct and easy PCB routing, the high integration rate and the option for the Auto-Eco functionality,” says Dr. Dirk Wittorf, marketing director of Integrated Discretes, NXP Semiconductors.

Mobile devices are in a transition from an analog video interface like CVBS (Color Video Baseband Signal) towards a digital interface like HDMI supporting HD (High Definition) resolution. To transmit video signals from mobile devices such as mobile phones, netbooks, tablet computers, notebooks, media players and digital cameras, the HDMI interface is frequently used in the latest designs. The HDMI interface provides the video and audio signals via the TMDS (Transition Minimized Differential Signaling) lines. These high-speed lines are typically protected by special multi-channel, low capacitance ESD protection diodes, which can be placed on the high speed lines in a “straight through routing” layout. In addition to the TMDS lines, the HDMI interface consists of the following control lines: DDC, which handles data transfer for content protection and TV resolution; CEC, which makes it possible to control several applications over one remote control; and HPD, which initiates the connection between the HDMI sink (for example, a receiver in a digital TV or projector) and the mobile device.

System chips for mobile applications typically run at lower voltage levels than the standardized 5V at the HDMI interface. The IP4791CZ12 provides bi-directional level shifting and buffering to bridge these different voltage levels.

The pins are protected with ESD protection diodes according IEC61000-4-2 level 4 (+/- 8kV contact). The IP4791CZ12 can be placed directly behind the HDMI connector on the PCB. Therefore, the energy of an ESD strike is directed towards the ground plane before reaching the HDMI transmitter. The integrated buffers have also a positive effect in case of ESD strikes. They do not pass on the remaining clamping voltage from the ESD strike to the SoC (system on a chip), thereby providing it with the best possible protection. These SoCs are manufactured in small node size CMOS processes for economy and speed, which makes robust ESD protection necessary. In addition, the buffers also block the EMI distortions on the DDC, CEC and the HPD lines.

For the HPD, DDC and CEC applications, pull up resistors and a CEC pull up current source with a very low leakage current are included as well. With this high integration concept, the system chip with the HDMI transmitter is connected directly over the IP4791CZ12 towards the HDMI port without the need for additional external components. This “clean interface” concept simplifies the PCB layout significantly, and reduces design time and effort for customers.

Due to the option for an Auto-Eco mode, there is no need for a dedicated GPIO pin on the system controller to supervise power management in the IP4791CZ12, as long as the design has no standby functionality, such as wake-up via CEC. Connecting the ACTIVE-pin to the HOTPLUG-pin on the connector automatically enables or disables the IP4791CZ12.

A design-in package is available, which includes example PCB layouts. The IP4791CZ12 is available in a thin QFN package: HXSON12 (2.1 x 2.5 x 0.5 mm), which is Pb-free and RoHS compliant.