Cygnal fabs single-chip USB to UART bridge

Mixed-signal chip maker Cygnal Integrated Products (Austin, Texas) now has available a power-managed USB-to-UART bridge chip. This IC is way cool, both literally and figuratively.

Dubbed the CP2101, it provides Universal Serial Bus 2.0 so-called full speed to 921.6-kbaud UART data transfers (it will also run at speeds down to 300 bits/s), thanks to separate 512 byte Transmit and Receive buffers.

What's more, the device can be self-powered or USB bus powered. As such, the CP2101 can be used for quickly updating legacy UART, RS-232, and RS485 systems with USB connectivity.

Cygnal's Signals

This device is in line with what Cygnal is known for, namely analog devices with high-speed digital blocks and flash on-chip. Indeed, this IC packs on-chip EEPROM that can be used to customize things such as USB Vendor ID, Product ID , a product description, string or power descriptor, a Device Release Number , and Device Serial Number .

The EEPROM is programmed on-board via USB, permitting the programming step to be integrated into the product during manufacturing and testing.

No External Parts

The 5 x 5-mm micro-lead-frame MLP-28 package is also easy to implement. It requires no external components. “The CP2101 needs no crystal, voltage regulator, or outboard EEPROM,” emphasizes Danny Allred, Cygnal's director of product marketing. “It also offers the smallest available circuit board footprint for a USB to UART bridge.”

Here's what the block diagram looks like:

Click for larger block diagram

An evaluation kit, priced at $49, is a USB-to-RS-232 approach that includes a board (with schematics and bill-of-material), cables, and royalty-free virtual COM port device drivers. Device drivers support Windows CE, Windows 98, Windows 2000, and Windows XP, as well as MAC OS-9 and MAC OS-X, and Linux 2.40 and above.

Faking Out A PC

The device drivers, provided by Silicon Laboratories, let a CP2101-based product to appear as a COM port to PC applications. The CP2101 UART implements all RS-232 signals, including control and handshaking signals, so existing system firmware doesn't need to be modified.

In many existing RS-232 designs, all that's required to update a design from RS-232 to USB is to replace the RS-232 level-translator with a CP2101.

A USB function controller in the CP2101 includes integrated transceiver and on-chip matching and pull-up resistors. The USB function controller manages all data transfers between the USB and the UART, as well as command requests generated by the USB host controller and commands for controlling the function of the UART.

What's more, USB Suspend and Resume signals are supported for power management of both the CP2101 device as well as external circuitry. The CP2101 will enter Suspend mode when Suspend signaling is detected on the bus.

Cygnal says its new CP2101 chips are priced at about $2.68 a pop in quantities of 10,000.

Both the eval kit and chips, are available on Cygnal's Web site.

For more info, contact Don Alfano at Cygnal Integrated Products, Inc., 4301 Westbank Dr., Building B, Suite 100, Austin, Texas 78746. Phone: 512-327-7088 Ext. 205. E-mail:

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