HMT235T

The HMT233, HMT234, HMT235 are used to applications that utilize the ISO 11898-compliant Controller Area Network (CAN) serial communication physical layer. As a CAN transceiver, each device is used in the differential CAN bus and the CAN controller, each device provides transmit and receive functionality at signaling speeds up to 1Mbps. Designed for operation in particularly harsh environments, these devices have cross-wire protection, over voltage protection up to ±40V, ground-failure protection, and thermal shutdown protection. These devices can operate over a wide common mode range of -7V to 12V. These transceivers are the interface between the host CAN controller on the microprocessor and the differential CAN bus used in industrial, building automation, transportation, and automotive applications that use differential CAN buses as the applications. Modes: The RS pin (pin 8) of the HMT233, HMT234 and HMT235 provides three modes of operation: high speed, slope control, and low power standby modes. Directly grounding pin 8 selects the high-speed mode of operation, which allows the driver output transistors to turn on and off as fast as possible with no limit on the rise and fall slopes. The rise and fall slopes can be adjusted by connecting a resistor between the RS pin and ground. The slope will be proportional to the output current of the pin. The device driver has a slew rate of approximately 15V/μs for a resistor value of 10kΩ and 2.0V/μs for a resistor value of 100kΩ. Loopback (HMT233): When the HMT233's loopback (LBK) pin (pin 5) is logic high, it places the bus outputs and bus inputs in a high impedance state. The D to R path inside the device remains active and can be used for driver-to-receiver loopback, enabling the self-diagnostic node function to be performed without disturbing the bus. Ultra-Low Current Sleep (HMT234): If a logic low is applied to the EN pin (pin 5), the HMT234 enters an ultra-low current sleep mode in which the driver and receiver circuits are deactivated. The device will remain in this sleep mode until the circuitry is activated by applying a logic high to pin 5. Auto-Baud Loopback (HMT235): The AB pin (pin 5) of the HMT235 implements a bus listen-only loopback feature that allows the local node controller to synchronize its baud rate with that of the CAN bus. In auto baud mode, the driver's bus output is in a high impedance state while the receiver's bus input remains active. The device has an internal loopback path from the D pin to the R pin to help the controller perform baud rate detection or autobaud functions.

Applications

• Industrial Automation, Controls, Sensors and Drive Systems
• Motor and Robot Control
• Building and temperature control (HVAC)
• Backplane communications and control
• CAN open, Device Net, CAN Kingdom, NMEA 2000, SAE J1939 and other CAN bus standard

Key features

• 3.3V single supply voltage
• Bus pin fault protection greater than ±40V
• Bus pin ESD protection greater than ±16KV HBM
• Data rates up to 1Mbps
• Extended common-mode range: -7V to 12V
• High input impedance supports 120 nodes
• LVTTL I/O withstands up to 5V
• Adjustable driver transition time improves radiated performance
• Unpowered nodes do not interfere with the bus
• Low current standby mode, 400μA (typical)
• HMT233: Loopback Mode
• HMT234: Ultra-low current sleep mode
• HMT235: Automatic Baud Loopback Mode
• Thermal Shutdown Protection
• No interference on bus inputs and outputs during power-up and power-down