The CP2101 is a highly integrated USB-to-UART bridge controller that provides a simple solution for updating RS-232 to USB using minimal components and PCB space design. The CP2101 includes a USB2.0 full-speed functional controller, USB transceiver, oscillator, EEPROM and an asynchronous serial data bus (UART) in a compact 5 x 5 mm QFN-28 package with complete modem control signals. No other external USB components are required.

Example System Diagram

The on-chip EEPROM can be used to customize the USB Vendor ID, Product ID, Product Description Strings required by OEM applications, Power Descriptor, Device Version Number and Device Serial Number. The EEPROM is programmed on-board via USB, allowing the programming steps to be easily integrated into the product manufacturing and testing process. A royalty-free Virtual COM Port (VCP) device driver from Silicon Laboratories allows the use of CP2101-based products to appear as a COM port for PC applications. The CP2101 UART interface implements all RS-232 signals, including control and handshake signals, so no existing system firmware needs to be modified. In many existing RS-232 designs, simply updating the design from RS-232 to USB will replace the RS-232 level translator with the CP2101. Provides direct access to driver support through the Silicon Laboratories USBXpress driver set.

The CP2101 is a mature product and is not recommended for new designs. The CP2102 is a pin and software compatible replacement for the CP2101. The CP2102 is recommended for all new designs.

Absolute Maximum Ratings

Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is only the pressure rating and functional operation of the equipment under those or any other conditions not implied in the operating list of this specification. Exposure to maximum rated conditions for extended periods of time may affect device reliability.

QFN-28 Pin Diagram (Top View)

QFN-28 Package Diagram

QFN-28 Package Dimensions

1All dimensions shown are in millimeters (mm) unless otherwise stated.

2. Complies with ANSI Y14.5M-1994 dimensions and tolerances.

3. This drawing conforms to JEDEC profile MO-243, variant VHHD, custom functions D2, E2, L, Z and Y are tolerances per vendor name.

4. The recommended card reflow profile is in compliance with JEDEC/IPC J-STD-020C Small Volume Specification Components.

Typical QFN-28 landing diagram

USB Function Controller and Transceiver

The Universal Serial Bus functional controller in the CP2101 is a USB 2.0 compliant full-speed device with integrated transceiver and on-chip termination and pull-up resistors. The USB function controller manages all data transfers between the USB and the UART as well as the USB generated command requests to the host controller and commands to control the UART function. Supports USB suspend and resume signals for power management of CP2101 devices

and external circuits. When a suspend signal is detected, the CP2101 will enter suspend mode on the bus. After entering suspend mode, CP2101 will send out SUSPEND and SUSPEND signals. SUSPEND and SUSPEND are also set after CP2101 reset until device configuration during USB

Enumeration complete

The CP2101 exits suspend mode when any of the following occurs: (1) a resume signal or generation is detected, (2) a USB reset signal is detected, or (3) a device reset occurs. When exiting suspend mode, the SUSPEND and SUSPEND signals are deasserted. During CP2101 reset, both SUSPEND and SUSPEND are temporarily floated high. If this is not desired, a strong pull-down (10kΩ) can be used to ensure that SUSPEND remains low during reset.

Typical Connection Diagram

Option 1: A 4.7kΩ pull-up resistor can be added for improved noise immunity.

Option 2: If powering other devices from the on-chip voltage regulator, you can add a 4.7µF capacitor.

Option 3: Avalanche TVS diodes can be added for ESD protection.

Option 3: Use Littlefuse p/n SP0503BAHT or equivalent.

Option 4: 10kΩ resistor to ground to hold SUSPEND low on initial power-up or device reset.

Asynchronous Serial Data Bus (UART) Interface CP2101 UART interface consists of TX (transmit) and RX (receive) data signals and data signals RTS, CTS, DSR, DTR, DCD and RI control signals. UART supports RTS/CTS, DSR/DTR and X-On/XOff handshake. The UART is programmable and supports various data formats and baud rates. If the driver is used for a virtual COM port, set the data format and baud rate during COM port configuration on the PC. If using the USBXpress driver, the CP2101 is configured through the USBXpress API.

The CP2101 contains an internal EEPROM that can be used to customize the USB Vendor ID (VID), Product ID (PID), Product Description String, Power Descriptor, Device Version Number and the number required by the device serial OEM application. If the EEPROM is not programmed with OEM data, use the configuration data shown in Table 7.1 for default values. While customization of USB configuration data is optional, it is recommended to customize the VID/PID combination. Unique VID/PID combination prevents the driver from conflicting with any other USB driver. It also recommends customizing the serial number to the same PC if the OEM application is one that can be used by multiple CP2101-based devices. The internal EEPROM is programmed via USB. This allows the OEM's USB configuration data and serial number of the CP2101 to be written on the board during manufacturing and testing. A separate utility for programming the internal EEPROM is available from Silicon Laboratories. Libraries can also use routines provided in the form of Windows® DLLs. This library can be used to integrate

EEPROM programming steps into custom software used by OEMs to simplify testing and serial number management during manufacturing. EEPROM has a typical endurance of 100,000 write cycles.

The CP2101 Virtual COM Port (VCP) device driver allows CP2101-based devices to appear on PC software applications as COM ports. Application software running on the PC accesses the CP2101 based device as it will access the standard hardware COM port. However, the actual data transfer between PCs CP2101 devices is performed via the USB interface. Therefore, existing COM port applications

Can be used to transfer data to CP2101 based devices via USB without modifying the application. See Application Note AN197: Example Code for Connecting CP2102 Using Virtual COM

The Silicon Laboratories USBXpress driver provides an alternative solution device for interfacing with the CP2102. No serial port protocol expertise required. Instead, a simple high-level application interface (API) is used to provide simpler CP201x connectivity and functionality. The USBXpress forCP210x development kit includes Windows device drivers, Windows device driver installers and uninstallers, and a host interface function library (host API) library (DLL) in the form of Windows dynamic linking. The USBXpress driver set is recommended for new products containing new PC software. Application Note "AN169: The USBXpress Interface Guidelines are described in the USBXpress Programmer's."

In addition to customizing the device as described in Chapter 7, "Internal EEPROM", it is also possible to customize the driver and driver installation package. See the application note "AN220: USB Driver Customization" for more information on generating custom VCP and USBXpress drivers.

The default driver included with the CP2101 is Microsoft WHQL (Windows Hardware Quality Labs) certified. This certification means that these drivers have been tested by Microsoft and its latest versions of the operating system (XP and Vista) will allow the drivers to be installed without any warnings or errors. Custom drivers generated using the AN220 software are not automatically certified. They must first go through the Microsoft driver reseller submission process. Please contact Silicon Laboratories for assistance with this process. Serial number 0001 (up to 63 characters)

The CP2101 includes an on-chip 5 to 3 V regulator. This allows the CP2101 to be configured as a USB bus powered device or as a USB self powered device. When enabled, the 3 V regulator output appears on the VDD pin and can be used to power external 3V devices. Regarding the electrical characteristics of the voltage regulator, or, if 3 V is supplied to the VDD pin, the CP2101 can be used as a USB self-powered device that disables the voltage regulator. For this configuration, it is recommended to use the REGIN input connected to a 3 V network to disable the voltage regulator. The USB maximum power and power attribute descriptors must match the device power usage and configuration.