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SP339

RS232/RS485/RS422 Transceiver with Internal Termination

The SP339 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 driver and one receiver (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 RS-485/422 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 Human Body Model (HBM) and ±8kV IEC-61000-4-2 Contact. Each receiver output has full fail-safe protection to avoid system lockup, oscillation, or indeterminate states by defaulting to logic-high output level when the inputs are open, shorted, or terminated but undriven. No external biasing resistors are required.

The RS-232 receiver inputs include a 5kΩ pull-down to ground. The RS-485/422 receiver inputs are high impedance (>96kΩ when termination is disabled), allowing up to 256 devices on a single communication bus (1/8th unit load).

The SP339E 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.

• Pin selectable Cable Termination
• No external resistors required for RS-485/422 termination and biasing
• 3.3V or 5V Single Supply Operation
• Robust ESD Protection on bus pins
  • ±15kV IEC 61000-4-2 (Air Gap)
  • ± 8kV IEC 61000-4-2 (Contact)
  • ±15kV Human Body Model (HBM)
• 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 Driver, 1 Receiver 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
• Space saving 6mm x 6mm QFN-40 Package
• Pin compatible with SP338E

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