SBASB59 July 2025 AMC0330S
PRODMIX
#d25e130 illustrates a simplified schematic of a circuit that senses the line voltages of a three-phase AC system. All three voltages are measured against neutral. This configuration allows the three AMC0x30S devices to share a common isolated power supply on the input side.
The AC line voltage on phase L1 is divided down to a ±1V level across the bottom resistor (RSNS) of a high-impedance resistive divider. The voltage across RSNS is sensed by the AMC0x30S (device 1). On the opposite side of the isolation barrier device 1 outputs a voltage proportional to the L1-to-neutral voltage. In the same way, device 2 and device 3 sense the L2 and L3 line voltages, respectively. A common VDD1 supply is generated from the low-voltage side by an isolated DC/DC converter circuit. A low-cost design is based on the push-pull driver SN6501 and a transformer that supports the desired isolation voltage ratings.