The MAX253ESA+ is a simple power-supply Transformer Driver for isolated RS-485/RS-232 data-interface applications. The device drives a centre-tapped transformer primary from a 5 or 3.3VDC power supply. The secondary can be wound to provide any isolated voltage needed at power levels up to 1W. The MAX253 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.
- 0.4μA Low-current shutdown mode
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