The THVD24x0 device enters shutdown mode to save power if both driver and receiver are disabled by setting the DE pin low and REB pin high. In shutdown mode, power consumption is only 0.1-μA typical without any load. Please note that the device takes a longer time to wake up from shutdown mode. For example, THVD2450 driver’s enable time is 2-μs from shutdown mode, while the enable time is 7-ns if the receiver is kept on. The same concept applies to the receiver enable time. The deglitch function is integrated in the enable pins to make them more robust in noisy environments. The specification is called t_SHDN (time to shutdown) and the following experiment shows how to interpret this value.

In this test (Figure 2-8), THVD2450 is set up in receiver mode with both DE and REB pin low. The receiver output is pull-down to ground with 4.7-kΩ resistor. With a 5-V supply, a 15-MHz 5-V peak to peak differential clock is fed to A and B pins.

With the disabled driver, the device will enter the shutdown mode if the receiver is also disabled. Because of the deglitch feature, the device does not shut down if the disable pulse at the REB pin (pin 2) is narrow. Figure 2-9 shows the THVD2450 receiver resumes working immediately as the REB pin toggles from high to low. This 212-ns glitch is filtered out so that the device does not shut down.

If the disable time is longer than the 500-ns maximum of t_SHDN in data sheet (Figure 2-10), the condition of both driver and receiver disabled makes THVD2450 enter shutdown mode. As the receiver is enabled, the wake-up time is about 2.2-μs. In many applications, DE and REB pins are shortened. Therefore, one GPIO pin of microcontroller can control the mode of the transceiver. From this experiment, it is clear that THVD24x0 will not enter shutdown mode by toggling this control pin. The same feature applies to the driver enable pin (DE – pin 3) as well. If the two enable pins are controlled separately, short glitches in enable pins will not make THVD24x0 shutdown either.