Shown on this slide is a fully functional LinkZero-AX circuit with a sensor connected to the bypass pin. To put the supply in off-mode, the power-down pulse turns on a transistor that connects the feedback pin to the bypass pin. This cuts off feedback to the device by pulling the feedback pin above the regulated 1.7 V. After feedback is lost for more than 160 switching cycles, the LinkZero-AX device enters off-mode. The power-down pulse must remain high for longer than 2.5 mS to provide enough time for at least 160 switching cycles. This long duration also ensures that noise or transients do not falsely trigger off-mode during normal operation. To wake the supply out of the off-mode, the bypass pin must be pulled below 1.5 V. There’s no minimum time for this signal, so only a few µS are needed. As soon as the bypass pin is pulled below 1.5 V and released, the LinkZero-AX device will immediately begin switching. During the off-mode, the bypass pin draws power from the drain pin to maintain regulation at 4 V.  Even though the bypass pin can source up to 500 µA, the aim should  be to keep the power drain from the bypass pin as low as possible, because any power draw will increase the standby consumption of the supply. During normal operation, the bypass pin can only source 85 µA of current at 5.8 V.  If the system requires more power, the customer can use a small bleed resistor circuit like the one shown on this slide to bias the rail. However, if the output voltage is too low to support 5.8 V plus a diode drop, it will be necessary to add a transformer bias winding to power the bypass pin circuits during normal operation.