California Micro Targets PCs with USB Overcurrent Protection Switches

11/13/2003 - California Micro Devices (NASDAQ: CAMD) announced three new USB overcurrent protection switches to support notebook and desktop personal computers, expanding its existing portfolio of USB ESD (electrostatic discharge) protection and power solutions. The CM3511/12/13 USB overcurrent switches support four USB ports in a single device. This allows next-generation PCs, which will have up to 8 ports per desktop, or 3-4 USB ports per notebook, to reduce the number of overcurrent protection devices per system by 50% vs. more traditional 2-port devices. The CM3511, CM3512, and CM3513 offer improved reliability and advanced features that are not available with other low-cost solutions such as Positive Temperature Coefficient (PTC) polymers, while providing comparable costs per port.

Advanced Port Protection Features
The CM3511 is optimized for systems supporting “wake-on-USB” functionality, and is the industry’s first solution with different current limits when the system is in full-power mode vs. standby mode. Two output channels are offered, with each channel supporting up to 2 USB ports. It provides 1.2A current limit per output channel in normal operating mode and 200mA current limit per output in system standby mode. This feature allows system designers to limit the amount of current a USB peripheral can draw when the system is in sleep mode, conserving power and preventing system crashes that can occur if a USB peripheral tries to draw too much current from a standby power rail.

The CM3512 also provides two output channels with a 1.2A current limit per channel. Separate ENABLE pins per channel allows independent channel control for improved power management. The CM3513 provides a single output channel and supports up to four ports on that channel with 2.4A current limit, simplifying design for customers that do not need the individual channel control of the CM3512.

All three switches have built-in backdrive protection, preventing self-powered USB devices from driving current back into the system, which can damage internal circuits when the system is powered down. A 10 ms deglitch “fault blanking interval” prevents false overcurrent alarms that could be caused during hot-insertion events or during short spikes of current such as can occur during initial spin-up of a USB hard drive.

Advantages over PTC Solutions
PTC devices have been a popular alternative to semiconductor overcurrent protection devices due to their low cost. The CM3511, CM3512, and CM3513 are designed to be cost-competitive with PTC implementations while overcoming their inherent limitations. PTCs, due to their chemical composition, exhibit operating changes over time and with temperature, and exhibit much slower response times than semiconductor solutions such as the CM3511, CM3512, and CM3513. Other features of the CM35XX family that are not available in PTC solutions include inrush current limiting, fault blanking protection, and current backdrive protection.

“Our customers have been searching for a solution with the advantages of semiconductor solutions at prices that are competitive with PTC devices,” stated Joe Salvador, director of marketing for computing and consumer products. “With the USB overcurrent switches we’re announcing today, they can build a cost-competitive solution without sacrificing critical protection features.”

Key Features and Benefits
Features of the CM3511/12/13 include:

Pricing and Availability
Evaluation boards and samples of the CM3511/12/13 devices will be available in mid-November. The CM3511/12/13 ICs are priced at $0.75 in 10,000 units. Volume production is scheduled for January, 2004.

About California Micro Devices Corporation
California Micro Devices Corporation is a leading supplier of application-specific analog semiconductor products for the mobile, computing, and consumer electronics markets. Key products include Application Specific Integrated Passive (ASIPTM) devices and power management ICs. Detailed corporate and product information may be accessed at

ASIPTM and Application Specific Integrated PassiveTM are trademarks of California Micro Devices.

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