The MAX3535E evaluation kit (EV kit) is a fully assembled and tested PCB that contains a 2500VRMS
isolated RS-485/RS-422 transceiver with ESD protection. The EV kit circuit features a differential driver and one receiver. The circuit’s receiver is a 1/8 unit load for the RS-485 bus and communicates up to 1000kbps. The MAX3535E fail-safe circuitry and driver slew-rate features are demonstrated and easily reconfigured.
Additionally, the EV kit features an H-bridge DC-DC converter to power the isolated section of the MAX3535E RS-485/RS-422 circuit. Input power to the circuit is supplied by a +3V to +5.5VDC source. This circuit uses a full-wave rectifier on the unregulated output and provides unregulated voltage to the MAX3535E internal, linear low-dropout (LDO) regulator. Using an H-bridge design minimizes input ripple current and radiated noise. Undervoltage lockout (UVLO) and thermal shutdown provide for a robust, isolated RS-485/RS-422 transceiver circuit and power supply. The surface-mount transformer provides up to 2500VRMS
galvanic isolation and the output is powered from a center-tapped, full-wave rectifier circuit to reduce output voltage ripple.
The isolated H-bridge DC-DC converter operation at 420kHz allows the use of ceramic-only output capacitors and a small transformer.
- Designed for 2500VRMS Isolation
- 1/8 RS-485 Unit Load
- 1000kbps Full-Duplex RS-485/RS-422 Communication (Configurable for Half Duplex)
- +3.0V to +5.5VDC Input Range
- Isolated VCC2 Output
- Center-Tapped, Full-Wave Rectifier Output
- 420kHz Switching Frequency
- Undervoltage Lockout (UVLO) and Thermal Shutdown
- Low-Cost Integrated-FET H-Bridge Design
- Fully Assembled and Tested