Buck controller for non-isolated step-down rails
The MAX1653ESE+ is a current-mode PWM buck controller from Analog Devices, designed to drive an external transistor pair for step-down conversion. Switching frequency is pin-selectable between 150 kHz and 300 kHz, and the controller supports clock synchronization to an external signal, which helps place switching harmonics outside sensitive bands in multi-rail systems. The 98% maximum duty cycle allows operation with small dropout between input and output, useful when the input rail sags near the regulation target.
Package, temperature grade, and lifecycle
The operating temperature range spans -40°C to +85°C, covering industrial and telecom ambient conditions.
Control features and integration note
On-chip control features include an Enable input for power sequencing and a Soft-Start pin to limit inrush current during startup. The soft-start ramp time is set by an external capacitor, giving the designer control over the output voltage slew rate. Because the controller uses an external transistor driver, the power-stage FETs are selected by the designer — the MAX1653ESE+ provides the gate drive logic but does not integrate the switches. This allows the output current rating to scale with the external MOSFETs rather than being fixed by the controller package.