SP3485EN-L

The SP3485EN-L from MaxLinear (formerly Exar/Sipex) is a 3.3V low-power half-duplex RS-485/RS-422 transceiver with a 10Mbps data rate. It is pin-compatible with the industry-standard 75176 transceiver, allowing direct replacement in existing designs. The BiCMOS process provides low power consumption without sacrificing performance. The driver outputs meet RS-485 specifications with a minimum 1.5V differential output across a 27Ω load. The receiver features ±200mV sensitivity with 20mV hysteresis for noise rejection, and a failsafe feature that guarantees a HIGH output when the inputs are open. The -7V to +12V common-mode range handles ground potential differences between systems. Up to 32 transceivers can share one bus. The EN-L suffix denotes the extended temperature range (-40°C to +85°C) in SOIC-8 package.

The SP3485EN-L operates as a half-duplex RS-485 transceiver where the driver and receiver share the same bus lines (A and B). In transmit mode, the driver enable (DE) is set high, and the receiver enable (RE) is set high (disabled). The driver takes the DI (data input) logic level and drives the A and B outputs as a differential pair: DI high drives A high and B low (positive VOD), DI low drives A low and B high (negative VOD). The differential output voltage is at least 1.5V across a 27Ω load, meeting the RS-485 specification. The driver is protected by current limiting to ±250mA for short-circuit conditions across the -7V to +12V common-mode range. In receive mode, DE is set low (driver outputs high-impedance) and RE is set low (receiver enabled). The receiver monitors the A-B differential voltage: when A-B exceeds +200mV, RO (receiver output) goes high; when A-B drops below -200mV, RO goes low. The 20mV hysteresis prevents output oscillation near the threshold in noisy environments. When the bus is idle (A-B between -200mV and +200mV, or inputs open), the failsafe circuit ensures RO is high. The device is pin-compatible with the 75176: pin 1=RO, pin 2=RE, pin 3=DE, pin 4=DI, pin 5=GND, pin 6=A, pin 7=B, pin 8=VCC.

SP3485EN-L uses the 8-SOIC (N) surface-mount package from MaxLinear/Sipex: Pin 1 = RO (Receiver Output), Pin 2 = RE (Receiver Enable, active-low), Pin 3 = DE (Driver Enable, active-high), Pin 4 = DI (Driver Input), Pin 5 = GND, Pin 6 = A (non-inverting bus), Pin 7 = B (inverting bus), Pin 8 = VCC (3.0-3.6V). This is the industry-standard RS-485 transceiver pinout shared by SP3485, SN75176, MAX3485, and similar half-duplex devices. For auto-direction control, tie RE and DE together — when DI is idle HIGH, the driver is enabled for transmit; when the controller releases DI, the bus returns to receive mode. The -L suffix denotes lead-free RoHS compliance. For 5V operation, use SP485 (identical pinout, 5V supply).

• Industrial Networks: 10Mbps supports high-speed Modbus RTU and Profibus; -7V to +12V CMR tolerates ground loops between factory equipment
• 楼宇自动化： 3.3V supply simplifies design with modern MCUs; 32-node capacity covers multi-floor sensor networks
• Smart Meters: Low 1mA supply current and 10µA shutdown extend battery life in remote meter reading nodes
• Legacy Upgrade: 75176 pin-compatible allows drop-in replacement of 5V transceivers with 3.3V systems
• Failsafe Operation: Open-bus failsafe (RO=HIGH) prevents garbage data during bus disconnection or cable faults

SP3485EN-L is a 3.3V 10Mbps RS-485 transceiver from MaxLinear in SOIC-8. The SP3481 provides full-duplex operation. The SP3491 offers 3.3V full-duplex with 10Mbps. The SN65HVD485EDR from TI provides 3.3V RS-485 in SOIC-8 with 16Mbps. The MAX3485ECSA+ from ADI/Maxim offers 3.3V 10Mbps with ESD protection. The THVD1500 from TI provides 3.3V RS-485 with 500kbps for long cable runs. For 5V operation, SP485 offers identical pinout at 5V supply.