5 Description (Continued)

R_S (pin 8) provides for three modes of operation: high-speed, slope control, or low-power standby mode. The high-speed mode of operation is selected by connecting R_S directly to ground, thus allowing the driver output transistors to switch on and off as fast as possible with no limitation on the rise and fall slope. The rise and fall slope can be adjusted by connecting a resistor to ground at R_S, because the slope is proportional to the output current of the pin. Slope control is implemented with a resistor value of 10 kΩ to achieve a slew rate of
≉ 15 V/μs, and a value of 100 kΩ to achieve ≉ 2 V/μs slew rate. For more information about slope control, refer to the Application and Implementation section.

The SN65HVD233 enters a low-current standby mode, during which the driver is switched off and the receiver remains active if a high logic level is applied to R_S. The local protocol controller reverses this low-current standby mode when it needs to transmit to the bus.

A logic high on the loopback (LBK, pin 5) of the SN65HVD233 places the bus output and bus input in a high-impedance state. The remaining circuit remains active and available for the driver to receiver loopback, self-diagnostic node functions without disturbing the bus.