Summary of Transceiver Chip Handles RS-232, RS-485 and RS-422
The SP335 is a multiprotocol transceiver supporting RS-232, RS-485, and RS-422 with integrated, pin-selectable cable termination and biasing—no external resistors required. It offers robust ESD protection, up to 20 Mbps (RS-485/422) and 1 Mbps (RS-232), selectable 250 kbps slew limiting, single-supply operation (3–5.5 V), low shutdown current, and flexible full/half duplex and mode configuration. Packaged in a 32-QFN, it suits industrial, embedded, and automation serial-port applications and requires only four external charge-pump capacitors for full operation.
Parts used in the SP335 Project:
- SP335 transceiver IC
- Four external charge pump capacitors
- Single supply (3 V to 5.5 V) power source
- VL logic supply (1.65 V to 5.5 V) connection
- Connector or cable for RS-232/RS-485/RS-422 interfaces
- PCB with 32 QFN footprint (5 mm x 5 mm)
- Pins or jumpers for MODE (RS-485/RS-232) selection
- Pin or jumper for TERM (termination enable)
- Pin or jumper for HALF/FULL duplex selection
- Pin or jumper for SLEW (250 kbps slew limiting)
SP335
RS-232/RS-485/RS-422 Transceiver with Internal Termination
- Pin-Selectable Cable Termination
- No External Resistors Required for RS-485/422 Termination or Biasing
- Robust ESD Protection:
- ±15kV IEC 61000-4-2 Air Gap Discharge
- ± 8kV IEC 61000-4-2 Contact Discharge
- ±15kV Human Body Model (HBM)
- 20Mbps RS-485 and 1Mbps RS-232 Data Rates
- Pin-Selectable 250kbps Slew Limiting
- Single Supply Operation from +3V to +5.5V
- 1.65V to 5.5V Logic Interface VL pin
- 2 Drivers, 2 Receivers RS-232/V.28
- 1 Driver, 1 Receiver RS-485/422
- Full or Half Duplex Configuration
- 1/8th Unit Load, up to 256 receivers on bus
- RS-485/422 Enhanced Receiver Fail-safe for open, shorted, or terminated but idle inputs
- 10nA Shutdown Supply Current (typical)
- Small 32 QFN package (5mm x 5mm)
- Software Programmable Serial Ports (RS-232, RS-422, RS-485)
- Industrial and Single Board Computers
- Industrial and Process Control Equipment
- Point-Of-Sale Equipment
- HVAC Controls and Networking Equipment
- Building Security and Automation
Description
The SP335 is an advanced multiprotocol transceiver supporting RS-232, RS-485, and RS-422 serial standards. Integrated cable termination and multiple 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/RS-232 mode pin selects RS-485 mode when high, and RS-232 mode when low. In RS-485 mode, the TERM pin enables the differential 120Ω termination, and the HALF/FULL pin configures the transceiver as either half or full duplex.
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) by setting the dedicated SLEW pin low.
For more detail: Transceiver Chip Handles RS-232, RS-485 and RS-422
- What serial standards does the SP335 support?
The SP335 supports RS-232, RS-485, and RS-422 serial standards. - Does the SP335 require external resistors for RS-485/422 termination or biasing?
No, the SP335 has integrated pin-selectable cable termination and requires no external resistors for RS-485/422 termination or biasing. - What data rates does the SP335 support?
The SP335 supports up to 20 Mbps in RS-485/422 modes and up to 1 Mbps in RS-232 mode. - Can the SP335 reduce EMI by limiting slew rate?
Yes, the SP335 offers pin-selectable 250 kbps slew limiting to minimize EMI when the SLEW pin is set low. - What supply voltages does the SP335 operate from?
The SP335 operates from a single supply of +3 V to +5.5 V and a VL logic interface from 1.65 V to 5.5 V. - How many drivers and receivers does the SP335 provide for RS-232 and RS-485/422?
For RS-232 the SP335 provides 2 drivers and 2 receivers; for RS-485/422 it provides 1 driver and 1 receiver. - Does the SP335 include ESD protection?
Yes, it provides robust ESD protection including ±15 kV IEC 61000-4-2 air gap, ±8 kV contact discharge, and ±15 kV HBM. - Is the SP335 configurable for full or half duplex?
Yes, a HALF/FULL pin configures the transceiver for either half or full duplex in RS-485 mode. - How many receivers can be supported on an RS-485 bus with the SP335?
The SP335 implements a 1/8th unit load, allowing up to 256 receivers on the bus. - What external components are needed for full operation of the SP335?
Full operation requires only four external charge pump capacitors.
