MaxLinear SP3490EN-L/TR

The SP3490 and SP3491 devices are +3.3V low-power full-duplex transceivers compliant with RS-485 and RS-422 serial protocol specifications. These devices are pin-to-pin compatible with the Exar SP490 and SP491 devices and popular industry-standard counterparts. The SP3490 and SP3491 utilize Exar's BiCMOS process, enabling low-power operation without sacrificing performance. Under load conditions, the SP3490 and SP3491 meet the electrical specifications of RS-485 and RS-422 serial protocols at data rates up to 10Mbps. The SP3491 is identical to the SP3490 with the addition of driver and receiver three-state enable lines.

The RS-485 standard is well suited for multipoint applications and long-distance interfaces. RS-485 supports up to 32 drivers and 32 receivers on a single data bus, making it ideal for multipoint applications. With cable lengths up to 4,000 feet, RS-485 transceivers feature a wide common-mode range (-7V to +12V) to accommodate ground potential differences. Because RS-485 is a differential interface, data is largely immune to transmission line noise.

The SP3490 and SP3491 drivers both feature differential outputs. The typical unloaded voltage output swing is 0V to VCC. In the worst case, with a 54Ω load on the differential output, the driver can sustain a voltage level greater than 1.5V. The SP3491 driver includes an active-high driver enable control line. A logic high on SP3491's DE (pin 4) enables the differential driver outputs. A logic low on DE (pin 4) places the driver outputs in a high-impedance (tri-state) condition. The SP3490 does not have a driver enable function.

The SP3490 and SP3491 receivers feature differential inputs with ±200mV input sensitivity. The receiver input impedance is typically 15kΩ (12kΩ minimum). The wide common-mode range (-7V to +12V) allows large ground potential differences between systems. Both the SP3490 and SP3491 receivers incorporate a failsafe feature that guarantees a logic high receiver output when the inputs are open. The SP3491 receiver includes an active-low enable control line. A logic low on SP3491's REB (pin 3) enables the differential receiver. A logic high on REB (pin 3) places the receiver in a tri-state condition.