SP3495E-3497E
14
HIGH SPEED +3.3V RS-485/RS-422 TRANSCEIVERS WITH +/-15KV ESD PROTECTION AND ADVANCED FAILSAFE REV. 1.0.0
1.0 PRODUCT DESCRIPTION
The SP349xE high speed transceivers contain one driver and one receiver. The SP3495 is a half-duplex
design while the SP3496E and SP3497E are full-duplex designs. The control pins RE
and DE feature a
hotswap capability allowing live insertion without spurious data transfer. Drivers are output short-circuit current
limited. Thermal-shutdown circuitry protects drivers against excessive power dissipation. When activited, the
thermal-shutdown circuitry forces the driver outptus into a high-impedance state.
Advanced Failsafe
The Receivers incorporate fail-safe circuitry, which guarantees a logic-high receiver output when the receiver
inputs are open or shorted, or when they are connected to a terminated transmission line with all drivers
disabled. In a terminated bus with all transmitters disabled the receivers differential input voltage is pulled to 0V
by the termination. The SP349xE interprets 0V differential as a logic high with a minimum 40mV noise margin.
HOT-SWAP CAPABILITY
When Vcc is first applied the SP349xE holds the driver enable and receiver enable inactive for approximately
10 microseconds. During power ramp-up other system IC’s may drive unpredictable values. Hot-swap
capability prevents the SP349xE from driving any output signal until power has stabilized. After the initial
power-up sequence, the hot-swap circuit becomes transparent and driver enable and receiver enable resume
their normal functions and timings
