WS339E

The WS339E is an advanced multiprotocol transceiver supporting RS- 232, RS- 485, and RS- 422 serial standards in a 40 pin QFN package. Integrated cable termination and four configuration modes allow all three protocols to be used interchangeably over a single cable or connector with no additional switching components. Full operation requires only four external charge pump capacitors. The RS- 485/422 modes feature one drivers and one receivers (1TX/1RX) in both half and full duplex configurations. The RS- 232 mode (3TX/5RX) provides full support of all eight signals commonly used with the DB9 RS- 232 connector. A dedicated diagnostic loopback mode is also provided. The high speed drivers operate up to 20Mbps in RS485/422 modes, and up to 1Mbps in RS- 232 mode. All drivers can be slew limited to 250kbps in any mode to minimize electromagnetic interference (EMI). All transmitter outputs and receiver inputs feature robust electrostatic discharge (ESD) protection to ± 15kV IEC- 61000- 4- 2 Air Gap, ± 8kV IEC- 61000- 4- 2 Contact, and ± 15kV Human Body Model (HBM). Each receiver output has full fail- safe protection to avoid system lookup, oscillation, or indeterminate states by defaulting to logic- high output level when the inputs are open, shorted, or terminated but undriven. The RS- 232 receiver inputs include a 5kΩ pull- down to ground. The RS- 485/422 receiver inputs are high impedance (>96kΩ) allowing up to 256 devices on a single communication bus (1/8th unit load). The WS339E operates from a single power supply, either 3.3V or 5V, with low idle current (2mA typical in all modes). The shutdown mode consumes less than 10μA for low power standby operation.

Applications

• Dual Protocol Serial Ports
• Industrial Computers
• Industrial and Process Control Equipment
• Point- Of- Sale Equipment
• Networking Equipment
• HVAC Controls Equipment

Key features

• Need external resistors required for RS- 485/422 termination and biasing
• Max Data Rate of 20Mbps in RS- 485/422 Modes and up to 1Mbps in RS- 232 Modes
• Pin selectable 250kbps Slew Limiting
• 3 Drivers,5 Receivers RS- 232/V.28
• 1 Drivers,1 Receivers RS- 485/422
• Full and Half Duplex Configuration
• 1/8th Unit Load, up to 256 receivers on bus
• RS- 485/422 Enhanced Failsafe for open, shorted, or terminated but idle inputs
• Robust ESD Protection on bus pins
• 15kV Human Body Model (HBM)
• 15kV EN61000- 4- 2 Air Gap Discharge
• 8kV EN61000- 4- 2 Contact Discharge