Negative rail from a positive input — what this charge pump does
The Analog Devices MAX889RESA+T is a charge-pump step-down regulator that generates a regulated negative output voltage from a positive input rail. It delivers up to 200 mA of output current at a switching frequency of 500 kHz, with the output adjustable from -2.5 V down to -5.5 V.
Adjustable output — setting the voltage
The output is adjustable via an external resistor divider, with a minimum output of -2.5 V and a maximum of -5.5 V. This covers the common negative-rail voltages needed for dual-supply op-amps (-5 V) or for generating a -3 V rail from a 3.3 V input. Because it is a charge pump rather than an inductive switching regulator, the design avoids the magnetic components and layout constraints of a buck-boost converter — just the pump capacitors and the output filter cap. No synchronous rectifier is used, so efficiency is lower than an inductor-based part, but the simplicity and small footprint often win for low-power negative rails.
Lifecycle and sourcing — still an active line item
The part is RoHS3 compliant.