The MAX668/MAX669 constant-frequency, pulse-width- modulating (PWM), current-mode DC-DC controllers are designed for a wide range of DC-DC conversion applica- tions 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 1.8V to 28V input voltage range 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. DC-DC conversion efficiency is optimized with a low 100mV current-sense voltage as well as with Maxim’s proprietary Idle Mode™ control scheme. The controller 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 oper- ating 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 boot- strapped operation (IC powered from boosted output). It supports output voltages up to 28V. The MAX668 oper- ates with inputs as low as 3V and can be connected in either a bootstrapped or non-bootstrapped (IC powered from input supply or other source) configuration.
The MAX668 and MAX669 are constant‑frequency, pulse‑width‑modulating (PWM) current‑mode DC‑DC controllers designed for step‑up, SEPIC, flyback, and isolated‑output configurations. They support a wide input range of 1.8 V to 28 V and can deliver power levels of 20 W or more with efficiencies exceeding 90 %.
Key features include an adjustable oscillator (100 kHz‑500 kHz), soft‑start, logic‑level shutdown, and Maxim’s proprietary Idle Mode for low‑load efficiency. Both devices are offered in a compact 10‑pin UMAX package and are available in automotive‑qualified and RoHS‑compliant versions.
| Input Voltage Range | 1.8 V to 28 V |
|---|---|
| Operating Frequency Range | 100 kHz to 500 kHz |
| Shutdown Supply Current | 3.5 pA |
| Efficiency | > 90 % |
| Package Type | 10‑pin UMAX |
| Maximum Power Dissipation (Ta = +70 °C) | 444 mW |
The MAX669 is guaranteed to start up at 1.8 V.
The shutdown supply current is 3.5 pA.
The oscillator can be set between 100 kHz and 500 kHz.