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Plain I?C bus to get speed makeover

Posted: 17 Jul 2006 ?? ?Print Version ?Bookmark and Share

Keywords:Dave Bursky? EE Times? Royal Philips Electronics? I² serial bus? Fast-mode Plus?

Proving that they can teach an old dog new tricks, designers at Royal Philips Electronics have upped the speed of the venerable I?C serial bus by 250 percent, thus improving data transfer speeds and response to control commands.

To support the new Fast-mode Plus (Fm+) 1MHz implementation of I?C, the company has crafted a family of Fm+ logic devices that can transfer data at 1Mbps, more than twice the speed of the current I?C specification. The chip designers were able to achieve the higher data rates by tightening the tolerances and bus-timing requirements.

The new standard is also backward-compatible with existing Fast-mode (400kHz) and standard-mode (10kHz) devices. Additionally, the Fm+ standard increases the total possible serial bus capacitance by a factor of 10, thus enabling longer-distance transmissions without requiring buffers at lower bus speeds. This allows system designers to create more flexible system implementations that run at higher speeds when more bandwidth is needed. And designers will also be able to use larger buses for emerging applications in LED and architectural lighting and gaming, which require a larger number of components on a single bus, said Dhwani Vyas, general manager of the interface product line at Philips Semiconductors.

"Fm+ will help designers improve performance across a wide range of I?C applications!especially as the bus is used more and more for system maintenance and the control of intelligent devices," said Vyas. The I?C bus!now the de facto standard for system control as the SMBus!is an elegant two-wire control bus with a software-defined protocol that provides the communication link between ICs in a system.

The Fm+ specification, released last month, takes the bus to the next level and will mark the first major update to the specification since January 2000.

Faster devices
The initial products developed by Philips to support the Fm+ standard include the PCA9633, a 4bit LED controller optimized for RGBA color mixing; and the PCA9698, an I/O expander that provides 40 general-purpose I/O lines. Also supporting the standard are the PCA9665, a parallel bus to I?C-bus controller; and the SC18IS600/601 and SC18IM700, which are master bridges compatible with Fm+ that convert the I?C-bus protocol to either SPI or UART asynchronous protocol.

Promising to greatly simplify programming and enable finer-grained control over LED animation and dimming in mobile, entertainment and lighting applications, the LED controller and driver packs four individual pulse-width-modulation (PWM) controllers!one for each LED output!and a fifth group PWM controller that can dim or blink all LEDs with the same value.

The chip also allows software programming of four addresses to which each LED PWM will respond, allowing group and subgroup calls when designers want to dim or blink groups of LEDs. Furthermore, the higher bus-drive capability of Fm+ allows up to 126 devices to operate on the same bus without requiring an extra bus extender on every node.

- Dave Bursky
EE Times

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