MAXREFDES1004, Boost, Single-Output, -73V to -35V Input, 5V/100mA Output DC-DC Converter Reference Design Using MAX668

MAXREFDES1004, Reference Design for the MAX668/MAX669 constant-frequency, pulse-width modulating (PWM), current-mode DC-DC controllers are designed for a wide range of DC-DC conversion applications, including step-up, SEPIC, flyback, and isolated-output configurations. Power levels of 20W or more can be controlled with conversion efficiencies of over 90%. The input voltage range of 1.8V to 28V supports a wide range of battery and AC-powered inputs. An advanced BiCMOS design features low operating current (220µA), adjustable operating frequency (100kHz to 500kHz), soft-start and a SYNC input, allowing the MAX668/MAX669 oscillator to be locked to an external clock. The MAX669 is optimized for low input voltages with a guaranteed start-up voltage of 1.8V. It requires bootstrapped operation (IC-powered from boosted output) and supports output voltages of up to 28V