When EN is de-asserted (low), the SN65DSI85 is in SHUTDOWN or RESET state. In this state, CMOS inputs are ignored, the MIPI® D-PHY inputs are disabled and outputs are high impedance. It is critical to transition the EN input from a low to a high level after the V_CC supply has reached the minimum operating voltage as shown in Figure 7-1. This is achieved by a control signal to the EN input, or by an external capacitor connected between EN and GND.

Figure 7-1 Cold Start V_CC Ramp up to EN

When implementing the external capacitor, the size of the external capacitor depends on the power up ramp of the V_CC supply, where a slower ramp-up results in a larger value external capacitor. See the latest reference schematic for the SN65DSI85 device and, or consider approximately 200 nF capacitor as a reasonable first estimate for the size of the external capacitor.

Both EN implementations are shown in Figure 7-2 and Figure 7-3.

Figure 7-2 External Capacitor Controlled EN

Figure 7-3 EN Input from Active Controller

When the SN65DSI85 is reset while V_CC is high, the EN pin must be held low for at least 10 ms before being asserted high as described in Table 7-5 to be sure that the device is properly reset. The DSI CLK lane MUST be in HS and the DSI data lanes MUST be driven to LP11 while the device is in reset before the EN pin is asserted per the timing described in Table 7-5.