The MAX253EPA+ is a transformer driver for isolated RS485 interface in 8 pin DIP package. It is a monolithic oscillator/power-driver specifically designed to provide isolated power for an isolated RS485 or RS232 data interface. The device drives a centre-tapped transformer primary from a 5V or 3.3V DC power supply. The secondary can be wound to provide any isolated voltage needed at power levels up to 1W. It consists of a CMOS oscillator driving a pair of N-channel power switches. The oscillator runs at double the output frequency, driving a toggle flip flop to ensure 50% duty cycle to each of the switches. Internal delays are arranged to ensure break before make action between the two switches. The SD pin puts the entire device into a low-power shutdown state, disabling both the power switches and oscillator. It is used in high noise-immunity communications interface, isolated and/or high-voltage power supplies and bridge ground differentials.
