General Description

The MAX848/MAX849 boost converters set a new standard of high efficiency and high integration for noise sensitive power-supply applications, such as portable phones and small systems with RF data links. The heart of the these devices is a synchronous boost-topology regulator that generates a fixed 3.3V output (or 2.7V to 5.5V adjustable output) from one to three NiCd/NiMH cells or one Li-Ion cell.

Synchronous rectification provides a 5 efficiency improvement over similar nonsynchronous boost regulators. In standby mode, pulse-skipping PFM operation keeps the output voltage alive with only 150μW quiescent power consumption. Fixed-frequency PWM operation ensures that the switching noise spectrum is limited to the 300kHz fundamental and its harmonics, allowing easy post-filtering noise reduction. For even tighter noise spectrum control, synchronize to a 200kHz to 400kHz external clock.

Feature

? Up to 95 Efficiency (see Typical Output Selector Guide below)

? 3.3V Dual Mode? or 2.7V to 5.5V Adj. Output

? 0.7V to 5.5V Input Range

? 0.15mW Standby Mode

? 300kHz PWM Mode or Synchronizable

? Two-Channel ADC with Serial Output

? Power-Good Function

Applications

? Digital Cordless Phones

? PCS Phones

? Cellular Phones

? Hand-Held Instruments

? Palmtop Computers

? Personal Communicators

? Local 3.3V to 5V Supplies

?