The MAX1673ESA+T is a charge-pump voltage converter from Analog Devices that takes a positive input between 2 V and 5.5 V and produces a regulated adjustable negative output down to -5.5 V. It is a step-down topology in the sense that the absolute output voltage magnitude is lower than the input magnitude, but the real trick is polarity inversion — it generates a clean negative rail from a single positive supply. The single output delivers up to 125 mA, switching at 350 kHz, and the output voltage is set with an external resistor divider. No synchronous rectifier here; the internal switches handle the pumping.
Where this charge pump fits in a design
This is a niche part for generating a negative rail in systems that only have a positive supply. Typical applications include biasing the substrate or back-gate of analog switches, providing a negative supply for single-supply op-amps that need to handle signals near ground, or generating the VGL rail for a small LCD display. The adjustable output from -1.5 V down to -5.5 V gives flexibility to set the exact voltage the load needs. The industrial temperature range means it can live in outdoor telecom gear, factory sensors, or engine-bay electronics without a problem.