V_SUP is the power supply pin. V_SUP is connected to the battery through an external reverse battery-blocking diode (see Figure 8-3). The V_SUP pin is a high-voltage-tolerant pin. Decoupling capacitors of 100 nF are recommended to be connected close to this pin to improve the transient performance. If there is a loss of power at the ECU level, the device has extremely low leakage from the LIN pin, which does not load the bus down. This is optimal for LIN systems in which some of the nodes are unpowered (ignition supplied) while the rest of the network remains powered (battery supplied). When V_SUP drops low enough the regulated output drops out of regulation. The LIN bus works with a V_SUP as low as 5.5 V, but at a lower voltage, the performance is indeterminate and not guaranteed. If V_SUP voltage level drops enough, it triggers the UV_SUP, and if it keeps dropping, at some point it passes the POR threshold.