Eliminating wide interconnect problems

Designers at National Semiconductor have developed a new serial interface for camera phones and small form factor displays dubbed the Mobile Pixel Link.

Wide, high speed parallel interfaces are used today for interconnect between baseband processors, application processors, image processors and the I/O devices they support such as camera and display modules.

But to reduce the size, ease the mechanical design, lower the power and electromagnetic interference, while at the same time reduce cost, some sort of serialised interface would be much preferred.

Recognising that fact, designers at National Semiconductor recently have developed the Mobile Pixel Link (MPL) physical layer, a first step in the standardisation process for a new serial interface for camera phones and small form factor displays.

The first version of the MPL physical layer is based on a low power, low EMI, single-ended current mode physical layer and a straightforward serialisation of legacy parallel interfaces. It solves problems created by having wide, high power, high-EMI video paths within handsets. It will allow all handset manufacturers to save money from cable size reductions, especially on expensive flex cables, and reduced IC package and connector sizes.

The MPL physical layer is a step toward MPL Level-1, which will be based on the same physical layer and offer an open packetised protocol that allows interoperability among multiple peripheral vendors.

Working with handset makers, National says that it anticipates completing the MPL Level-1 standard through an ad-hoc consortium or a recognised international standard’s body such as the existing Mobile Industry Processor Interface (MIPI) alliance, a collaboration of mobile industry leaders with the objective to define and promote open standards for interfaces to mobile application processors.

Founded by ARM, Nokia, STMicroelectronics and Texas Instruments in July last year as an evolution of the OMAPI Standard, the MIPI Alliance is intended to complement existing standards bodies such as the Open Mobile Alliance and 3GPP, with a focus on microprocessors, peripherals and software interfaces.

To accelerate the adoption of its MPL technology, National has released engineering samples for two products, the LM2501 and LM2502.

The LM2501 device is a Serialiser/Deserialiser that adapts existing video busses to Mobile Pixel Link (MPL). Contained in a 24 lead Ultra CSP Package, the Serialiser resides beside the video source (camera) and translates the parallel bus from LVCMOS levels to serial MPL levels for transmission over a flex cable to the Deserialiser located by the respective destination Video Input Port.

The LM2502 device is a dual link Transceiver that adapts existing CPU/video busses to a low power current-mode serial MPL link. The Master Transceiver resides beside an application processor or baseband processor and translates a parallel bus from LVCMOS levels to serial MPL levels for transmission over a flex cable and PCB traces to a Slave Transceiver located near the display module.

National’s MPL initiative has already received attention from industry leaders.

‘Philips Mobile Display Systems recognises amongst its customer base a growing demand for a high-speed serial display interface solution such as MPL,’ said Johan van de Ven, Chief Technology Officer of Philips MDS.

‘The ability to interconnect subcomponents within a phone cheaply, reliably and in a small form factor becomes more and more of a challenge,’ said Kazuaki Takanose, Corporate Vice President of Sony-Ericsson. ‘MPL looks as though it will give the industry a way of doing this in a standardised way, enabling multiple sourcing.’