LinkZero-AX is the latest member of the LinkSwitch family of integrated offline switcher ICs from Power Integrations. The unique feature of this product is the ability to consume less than 4 mW in the off-mode. When the feedback pin is pulled high for longer than 2.5 mS, the LinkZero-AX IC enters the off-mode. In the off-mode, the LinkZero-AX device stops switching and the output voltage falls. An internal voltage regulator supplied from the drain pin maintains a constant voltage on the bypass pin. Pulling the bypass pin to ground provides the reset signal to restart the supply. Putting the LinkZero-AX device into the off-mode sends the supply into a deep sleep, reducing the total amount of input power consumed to 0.00 watts. LinkZero-AX can be used in both isolated and non-isolated designs. In isolated designs, an opto-isolator can provide both the feedback and power-down signals. LinkZero-AX provides a very simple circuit for controlled power-down and wake-up. Since this method doesn’t use any relay circuits the AC supply is always connected to the entire system, including the auxiliary power supply and EMI filter. A typical appliance circuit may use X-capacitor discharge resistors in the EMI filter, and line sense resistors for the microcontroller which would be a constant load on the input, even during the off-mode. For the lowest possible standby power, CAPZero and SENZero devices should be used to disconnect the discharge resistors and sense resistors when not in use.