A novel active feedback flyback with only 100-mV inductive overshoot for a standard low-voltage CMOS inductive load driver, in a single-chip controller for 73 relays in a POTS/ADSL splitter application

This paper presents an inductive load driver. The circuit is realized in a standard low-voltage CMOS process: as the coil freewheels when the driver is switched off, the circuit clamps the output voltage at 100 mV above the power supply. Hence, no high-voltage technology or high-voltage tolerant circuit is required. 73 drivers are integrated in an ASIC, controlling 73 relays for a test access function on a POTS/ADSL splitter filter board. The driver also performs output voltage slope control and has an elegant, effective short-circuit protection.