MAX669

The MAX668/MAX669 constant-frequency, pulse-widthmodulating (PWM), current-mode DC-DC controllers are designed for a wide range of DC-DC  onversion applications including step-up, SEPIC, flyback, and isolatedoutput configurations. Power levels of 20W or more can be controlled with conversion efficiencies of over 90%. The 1.8V to 28V input voltage range of MAX669  supports a wide range of battery and AC-powered inputs. An advanced BiCMOS design features low   erating 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.

DC-DC conversion efficiency of MAX669 is optimized with a low 100mV current-sense voltage as well as with Maxim's proprietary Idle Mode™ control scheme. The controller MAX669 operates in PWM mode at medium and heavy loads for lowest noise and optimum efficiency, then pulses only as needed (with reduced inductor current) to reduce operating current and maximize efficiency under light loads. A logic-level shutdown input is also included, reducing supply current to 3.5µA.

The MAX669, optimized for low input voltages with a guaranteed start-up voltage of 1.8V, requires bootstrapped operation (IC powered from boosted  utput). It supports output voltages up to 28V. The MAX668 operates with inputs as low as 3V and can be connected in either a bootstrapped or non- ootstrapped (IC powered from input supply or other source) configuration. When not bootstrapped, MAX669 has no restriction on output voltage. Both ICs are  vailable in an extremely compact 10-pin µMAX package.