1 to 3 Cell, High Current, Low-Noise, Step-Up DC-DC Converters with Linear Regulator

The MAX1705/MAX1706 are high-efficiency, low-noise, step-up DC-DC converters with an auxiliary linear-regulator output. These devices are intended for use in battery-powered wireless applications. They use a synchronous rectifier pulse-width-modulation (PWM) boost topology to generate 2.5V to 5.5V outputs from battery inputs, such as 1 to 3 NiCd/NiMH cells or 1 Li-Ion cell. The MAX1705 has an internal 1A n-channel MOSFET switch. The MAX1706 has a 0.5A switch. Both devices also have a built-in low-dropout linear regulator that delivers up to 200mA.

With an internal synchronous rectifier, the MAX1705/MAX1706 deliver 5% better efficiency than similar non-synchronous converters. They also feature a pulse-frequency-modulation (PFM) standby mode to improve efficiency at light loads, and a 1µA shutdown mode. An efficiency-enhancing track mode reduces the step-up DC-DC converter output to 300mV above the linear-regulator output.

Both devices come in a 16-pin QSOP package, which occupies the same space as an 8-pin SO. Other features include two shutdown-control inputs for push-on/push-off control, and an uncommitted comparator for use as a voltage monitor.

Applications

* Digital Cordless Phones * Handheld Instruments (PDAs, Palmtops) * Palmtop Computers * PCS Phones * Personal Communicators * Two-Way Paging * Wireless Handsets

* Up to 96% Efficiency

* 1.1VIN Guaranteed Startup

* Up to 850mA Output (MAX1705)

* Step-Up Output (2.5V to 5.5V Adjustable)

* Linear Regulator (1.25V to 5.0V Adjustable)

* PWM/PFM Synchronous-Rectified Topology

* 300kHz PWM Mode or Synchronizable

* 1µA Shutdown Mode

* Voltage Monitor

* Pushbutton On/Off Control