Low-power chip solution realizes HDMI to VGA output conversion

Since its release, the HDMI interface standard has been adopted by a variety of products, including digital TVs, set-top boxes, Blu-ray players, and game consoles, and has become the de facto connectivity standard for LCD TVs and other advanced digital devices. So far, there have been more than 1,000 authorized adopters.

According to the forecast of industry research institute In-Stat, by 2012, the shipment of HDMI interface equipment will exceed 600 million units, of which digital TVs, set-top boxes, DVD players, Blu-ray players and PCs will become the mainstream applications of HDMI. According to IHSiSuppli research data, multiple factors are driving the HDMI market, including the increase in content in digital formats, the growth in the number of monitors and audiovisual equipment that support digitally encoded content, and the continued development of 1080p full HD televisions. In 2011, the global shipments of HDMI-enabled equipment manufacturers will increase from 477.7 million in 2010 to 629.1 million, an increase of 44%. The growth rate will slow down in the next three years, but will remain at 20-35%, and by 2014, there will be about 1.3 billion devices using HDMI interface.

As more and more devices support HDMI or DP output, CRT TVs and VGA monitors in users’ homes are faced with an embarrassing situation. On the one hand, it is a pity to throw away the existing devices; TVs or monitors are not cheap these days. To this end, Longxun semiconductor has developed a new generation of low-power HDMI/DP to VGA/YPbPr chip LT8511, which can help users easily solve the interconnection problem between HDMI/DP playback devices and VGA/YPbPr Display devices.

LT8511 Internal Architecture

The internal architecture of the LT8511 chip is shown in Figure 1, which mainly includes HDCP engine, HDMI receiver, video decoding engine and audio decoding engine. Based on Longxun’s unique ClearEdge technology, LT8511 adopts 0.18μm CMOS process, which combines high performance, low power consumption, high integration and low cost; supports 2.475Gbps transmission speed and supports 8-bit, 10-bit and 12-bit color depth .

Low-power chip solution realizes HDMI to VGA output conversion

Figure 1: The internal structure of the LT8511 chip.

Main technical features

1. LT8511 integrates HDMI receiver PHY (Longxun has its own HDMI1.3 transmitter and HDMI1.3 receiver IP), which can receive HDMI and dual-mode DP differential signals. At the same time, the PHY can perform EQ processing on the signal, which can ensure good reception of long-distance high-speed signals.

2. The LT8511 integrates an on-chip termination resistor (ODT), which can improve the quality of the received signal and save the system cost.

3. The LT8511 integrates a high-bandwidth digital content protection (HDCP) engine and an internal ROM to store the device key to ensure normal communication with HDCP-encrypted playback devices (such as Blu-ray, PS3).

4. In terms of video processing, it can convert between RGB and YCbCr, and supports SOG mode. LT8511 integrates a 10-bit DAC to support high-resolution video formats to achieve better Display effects.

5. The LT8511 integrates a separate audio phase-locked loop, which can separate the audio signal from the HDMI data stream, and supports two audio formats, I2S and SPDIF.

6. The LT8511 integrates a cache to store various formats of information, and also supports reading from an external MCU through I2C, providing users with flexible options.

Application prospect

At present, the related products on the market are mainly based on DP to VGA. Since DP can provide large power, the problem of IC power consumption is not difficult. However, for HDMI to VGA products, an external power supply is almost always used at present. Since the power provided by various HDMI transmitters on the market is different and not high, and the common mode potential of HDMI and DP is different, chip manufacturers must provide Different product lines offer different chips.

The emergence of the LT8511 chip enables customers to quickly and easily implement products with multiple integrated interfaces and reduce the cost of use for users. The LT8511 supports the dual interface format of HDMI 1.3a and Dual Mode DP1.1, which can solve the interconnection problem between HDMI/DP and traditional VGA/YPbPr devices. In addition, Longxun insists on providing a design solution without external power supply, which is convenient for customers on the one hand; Under the 1080P 8-bit audio and video transmission specification, the power consumption of the LT8511 is 3.3V@260mA, and there are many opportunities in applications without external power supply.

According to different needs of customers, LT8511 can realize a variety of applications, suitable for all HDMI to VGA applications; for Apple products, it can realize dock to VGA output, which needs to be matched with an Apple-specific identification IC.

System Design Considerations

When using the LT8511 for application system design, the following issues must be paid attention to:

1. The power supply voltage of LT8511 has two types: 3.3v and 1.8v. Various power lines and ground lines should be separated;

2. HDMI differential signal line needs 100 ohm impedance matching and equal-length processing;

3. The LT8511 chip integrates ESD protection, anti-static up to 4KV, and the peripheral circuit can not need to add an ESD protection chip.

Summary of this article

LT8511 is a chip product specially designed for connecting HDMI/DP equipment and VGA/YPbPr terminal display equipment. The difficulty in the design of this chip lies in integrating an HDMI receiver and supporting HDCP decryption. At the same time, it integrates a 10-bit DAC. Compatible with VGA/YPbPr, it solves the problem of interconnection between new-generation HDMI/DP equipment and outdated VGA/YPbPr terminal equipment for consumers, saving customers’ use cost.