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