STC3485E Datasheet, PDF (8/11 Pages) List of Unclassifed Manufacturers – 3.3V-Powered, ±15kV ESD-Protected, and Slew-Rate-Limited True RS-485 Transceivers

Applications Information
The STC3485E is low-power transceivers for RS-485 communications. The STC3485E can transmit and receive at data rates up to
500kbps. The STC3485E is half-duplex. Driver Enable (DE) and Receiver Enable (/RE) pins are included on the STC3485E. When
disabled, the driver and receiver outputs are high impedance.
Reduced EMI and Reflections
The STC3485E is slew-rate limited, minimizing EMI and reducing reflections caused by improperly terminated cables. Figure 11
shows the output waveform of the slew-rate-limited STC3485E transmitting a 125kHz signal, as well as the Fourier analysis of that
waveform. The high-frequency harmonics have much lower amplitudes, and the potential for EMI is significantly reduced.
Low-Power Shutdown Mode
A low-power shutdown mode is initiated by bringing both /RE high and DE low. The devices will not shut down unless both the
driver and receiver are disabled (high impedance). In shutdown, the devices typically draw only 1µA of supply current. For these
devices, the tPSH and tPSL enable times assume the part was in the low-power shutdown mode; the tPZH and tPZL enable times
assume the receiver or driver was disabled, but the part was not shut down.
Figure 11. Driver Output Waveform and FFT Plot of
STC3485E Transmitting a 125kHz Signal
Figure 12. STC3485E Driver Propagation Delay
Figure 13. STC3485E Receiver Propagation Delay
Figure 14. STC3485E System Differential Voltage
at 125kHz Driving 4000 ft of Cable