Created: May 31, 2017
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The CP2102N is a highly-integrated USB 2.0 to UART (RS232) bridge controller designed to simply add USB to your applications by removing firmware difficulty and diminishing development time. It provides an easy way of improving RS-232 designs to USB using few external components and smaller PCB size. The CP2102N includes a USB 2.0 full-speed function controller, USB transceiver, oscillator, and Universal Asynchronous Receiver/Transmitter (UART) in packages as small as 3mmx3mm. No other external USB components are required for development. The device operating supply voltage ranges from 3V up to 5.25V. It typically consumes 9.5mA when transmitting at 1.152Mbaud and 13.7mA at 3Mbaud.
This reference design is a typical application circuit for the CP2102N device. It only uses few capacitors for power supply filtering and one resistor for limiting LED current. The main components used in this design are the CP2102N controller and the SP3243EU RS-232 transceiver. The CP2102N has an internal USB function controller and UART. 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. In this design, the SP3243EU handles the UART outputs of the CP2102N. The SP3243EU drivers convert the outputs of the CP2102N UART to a 5V EIA/TIA-232 level to interface with RS-232 devices. On the other side, the outputs of the RS-232 device which are fed to the RS-232 inputs of SP3243EU are converted by the internal receivers of the SP3242EU to interface with the UART of the CP2102N.
The CP2102N has a Suspend mode that can be used for power management of the device as well as external circuitry. The Suspend mode is started when Suspend signaling is detected on the USB. On Suspend mode, the CP2102N asserts the SUSPEND and SUSPENDb signals. In this design, the /SUSPEND pin of the CP2102N which outputs a LOW signal when device enters Suspend mode is connected to the /SHUTDOWN pin of the SP3243EU device. The /SHUTDOWN driver overrides the AUTO ON-LINE circuitry of the SP3243EU device which makes the device enter into shutdown or standby mode.