MAXIM MAX668EUB+T

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 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 operating current and maximize efficiency under light loads. A logiclevel 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 output). It supports output voltages up to 28V. The MAX668 operates with inputs as low as 3V and can be connected in either a boot­ strapped or non-bootstrapped (IC powered from input sup­ ply or other source) configuration. When not bootstrapped, it has no restriction on output voltage. Both ICs are avail­ able in an extremely compact 10-pin μMAX package.

• 1.8V Minimum Start-Up Voltage (MAX669)
• Wide Input Voltage Range (1.8V to 28V)
• Tiny 10-Pin μMAX Package
• Current-Mode PWM and Idle Mode Operation
• Efficiency over 90%
• Adjustable 100kHz to 500kHz Oscillator or SYNC Input
• 220μA Quiescent Current
• Logic-Level Shutdown
• Soft-Start

• Cellular Telephones
• Telecom Hardware
• LANs and Network Systems
• POS Systems