General Description

The MAX3051 interfaces between the CAN protocol controller and the physical wires of the bus lines in a controller area network (CAN). The MAX3051 provides differential transmit capability to the bus and differential receive capability to the CAN controller. The MAX3051 is primarily intended for +3.3V single-supply applications that do not require the stringent fault protection specified by the automotive industry (ISO 11898).
The MAX3051 features four different modes of operation: high-speed, slope-control, standby, and shutdown mode. High-speed mode allows data rates up to 1Mbps. The slope-control mode can be used to program the slew rate of the transmitter for data rates of up to 500kbps. This reduces the effects of EMI, thus allowing the use of unshielded twisted or parallel cable. In standby mode, the transmitter is shut off and the receiver is pulled high, placing the MAX3051 in low-current mode. In shutdown mode, the transmitter and receiver are switched off.
The MAX3051 input common-mode range is from -7V to +12V, exceeding the ISO 11898 specification of -2V to +7V. These features, and the programmable slew-rate limiting, make the part ideal for nonautomotive, harsh environments. The MAX3051 is available in 8-pin SO and SOT23 packages and operates over the -40°C to +85°C extended temperature range.

 

Benefits and Features

● Use 3V Microcontroller with Same LDO
• Low +3.3V Single-Supply Operation
● Common-Mode Range Exceeds the ISO 11898 Standard (-2V to +7V)
• Wide -7V to +12V Common-Mode Range
● Uses Minimal Board Space
• SOT23 Package
● Flexible Operation Optimizes Performance and Power Consumption for Reduced Thermal Dissipation
• Four Operating Modes
High-Speed Operation Up to 1Mbps
Slope-Control Mode to Reduce EMI (Up to 500kbps)
Standby Mode
Low-Current Shutdown Mode
● Robust Protection Increases System Reliability
• ±12kV Human Body Model ESD Protection
• Thermal Shutdown
• Current Limiting

 

Applications

● Printers JetLink
● Industrial Control and Networks
● Telecom Backplane
● Consumer Applications

 

Detailed Description

The transceivers operate from a single +3.3V supply and draw 35μA of supply current in dominant state and 2μA in recessive state. In standby mode, supply current is reduced to 8μA. In shutdown mode, supply current is less than 1μA.
CANH and CANL are output short-circuit current limited and are protected against excessive power dissipation by thermal-shutdown circuitry that places the driver outputs into a high-impedance state.

 

Receiver

The receiver reads differential inputs from the bus lines (CANH, CANL) and transfers this data as a single-ended output (RXD) to the CAN controller. It consists of a comparator that senses the difference VDIFF = (CANH – CANL) with respect to an internal threshold of +0.75V. If this VDIFF is greater than 0.75, a logic-low is present at RXD. If VDIFF is less than 0.75V, a logic-high is present. The receiver always echoes the CAN BUS data.
The CANH and CANL common-mode range is -7V to +12V. RXD is logic-high when CANH and CANL are shorted or terminated and undriven.

 

Mode Selection

High-Speed Mode

Connect RS to ground to set the MAX3051 to highspeed mode. When operating in high-speed mode, the MAX3051 can achieve transmission rates of up to 1Mbps.
In high-speed mode, use shielded twisted pair cable to avoid EMI problems.

 

Standby Mode

If a logic-high is applied to RS, the MAX3051 enters a low-current standby mode. In this mode, the transmitter is switched off and the receiver is switched to a low- current/low-speed state. If dominant bits are detected, RXD switches to low level. The microcontroller should react to this condition by switching the transceiver back to normal operation.
When the MAX3051 enters standby mode, RXD goes high for 4μs (max) regardless of the BUS state.
However, after 4μs, RXD goes low only when the BUS is dominant, otherwise RXD remains high (when the BUS is recessive). For proper measurement of standby-to- receiver active time (tSBRXDL), the BUS should be in dominant state.