ElecSuper MAX3471EUA+T(ES)

The MAX3471EUA+T(ES) is a 5V-powered, ±15kV ESD-protected, slew-rate-limited differential transceiver with full RS-485 compatibility. Each device contains one driver and one receiver, designed for data transmission with an extended common-mode range (-7V to 12V). The slew-rate-limited driver minimizes EMI and reduces reflections caused by improper cable termination.

The MAX3471EUA+T(ES) also features enhanced ESD protection. All transmitter outputs and receiver inputs withstand ±15kV using the IEC61000-4-2 air-gap discharge method, ±15kV using the Human Body Model, and ±8kV using the IEC61000-4-2 contact discharge method.

The driver incorporates short-circuit current limiting. When the driver output enters a high-impedance state due to the thermal shutdown circuit, the driver prevents excessive power dissipation. The receiver input failsafe feature ensures a logic-high output when both inputs are open, shorted, or idle.

Both devices feature power-up/power-down modes with glitch-free driver outputs, allowing hot insertion or removal of transceivers on a live data bus. The CMOS design significantly reduces power consumption without sacrificing immunity to bus contention or ESD damage. Typical quiescent current is only 300μA during operation and 1μA in shutdown mode. The MAX3471EUA+T(ES) is designed for half-duplex communication in an SOP8 package.

The MAX3471EUA+T(ES) is a low-power transceiver for RS-485 communication, supporting error-free data transmission at up to 0.5Mbps in half-duplex mode. It includes Driver Enable (DE) and Receiver Enable (/RE) pins. When disabled, both driver and receiver outputs are high-impedance.

When the receiver inputs are shorted, open, or connected to a terminated transmission line with all drivers disabled, the MAX3471EUA+T(ES) guarantees a logic-high receiver output. This is achieved by setting the receiver threshold between -50mV and -200mV. If the differential receiver input voltage (A-B) is greater than or equal to -50mV, RO is logic high; if A-B is less than or equal to -200mV, RO is logic low. On a terminated bus with all transmitters disabled, the differential input voltage is pulled to 0V by the termination resistor. Due to the receiver threshold setting of the MAX3471EUA+T(ES), this results in a logic-high output with a minimum noise margin of 50mV. Unlike previous failsafe devices, the -50mV to -200mV threshold complies with the ±200mV EIA/TIA-485 standard.

As with all ElecSuper devices, all pins of the MAX3471EUA+T(ES) incorporate ESD protection structures to guard against electrostatic discharge encountered during handling and assembly. The driver outputs and receiver inputs provide additional ESD protection. ElecSuper engineers have developed advanced structures that protect these pins from ±15kV ESD damage without degradation. The ESD-protected pins are tested relative to ground in the powered-down state, withstanding ±15kV using the Human Body Model.

The standard RS-485 receiver input impedance is 12kΩ (one unit load), and a standard driver can drive up to 32 unit loads. ElecSuper series transceivers feature a receiver input impedance of 1/8 unit load (96kΩ), allowing up to 256 transceivers to be connected in parallel on a single communication line. Any combination of these devices and/or other RS-485 transceivers may be connected to the line, provided the total unit load does not exceed 32.

The MAX3471EUA+T(ES) employs slew-rate limiting to minimize EMI and reduce reflections caused by improper cable termination. In general, the transmitter rise time is directly related to the length of unterminated stubs.

• ESD protection for RS-485 input/output pins
• ±15kV ESD protection on RS-485 input/output pins (Human Body Model)
• 5V supply voltage range
• Enhanced slew rate limiting for error-free data transmission
• 1μA low-current shutdown mode
• Common-mode input voltage range: -7V to +12V
• Supports up to 256 transceivers on the bus
• Thermal shutdown protection
• Driver current limiting for overload protection
• Data rate up to 0.5Mbps

• Telecom
• Low-power RS-485 transceivers
• ISDN
• Industrial control LAN
• Transceivers for EMI-sensitive applications
• Packet switching
• Level shifters