View max668-max669 datasheet:

19-4778; Rev 0a; 8/98 1.8V to 28V Input, PWM Step-Up Controllers in µMAX General Description Features The MAX668/MAX669 constant-frequency, pulse-width- 1.8V Minimum Start-Up Voltage (MAX669) modulating (PWM), current-mode DC-DC controllers are Wide Input Voltage Range (1.8V to 28V) designed for a wide range of DC-DC conversion applica- tions including step-up, SEPIC, flyback, and isolated- Tiny 10-Pin µMAX Package output configurations. Power levels of 20W or more can Current-Mode PWM and Idle Mode™ Operation be controlled with conversion efficiencies of over 90%. Efficiency over 90% The 1.8V to 28V input voltage range supports a wide range of battery and AC-powered inputs. An advanced Adjustable 100kHz to 500kHz Oscillator or BiCMOS design features low operating cu