In the LinkZero-AX circuit shown on this slide, the supply enters the off-mode when a power-down signal is used to turn on a simple BJT switch connecting the feedback pin to the bypass pin. During normal operation, the bypass pin operates at 5.8 V. Connecting it with the feedback pin will raise the entire rail above 1.7 V, cutting off feedback to the device. Once the LinkZero-AX device has gone 160 cycles without feedback, it will enter the off-mode. The power-down pulse must be longer than 2.5 mS to allow sufficient margin for the full 160 skipped cycles. LinkZero-AX ICs will always enter the off-mode if feedback is not received for more than 160 switching cycles. This means it is possible for a step down in load to induce an unwanted shutdown by causing a voltage swell on the output that may take longer than 2.5 mS to reduce. To prevent this from happening, a small preload resistor can be added to the output to decrease output capacitor discharge time in case of a voltage spike. Once the supply is in the off-mode, waking it up is as simple as grounding and releasing the bypass pin, using either a soft-switch or a BJT. As soon as the voltage on the bypass pin passes below 1.5 V and is released, the pin will recharge to its normal operating voltage of 5.8 V. When it gets there, the LinkZero-AX device will immediately begin switching to bring the output voltage back into regulation.