General Description

The MAX856–MAX859 are high-efficiency, CMOS, step-up, DC-DC switching regulators for small, low input voltage or battery-powered systems. The MAX856/MAX858 accept a positive input voltage between 0.8V and VOUT and convert it to a higher, pin-selectable output voltage of 3.3V or 5V. The MAX857/MAX859 adjustable versions accept 0.8V to 6.0V input voltages and generate higher adjustable output voltages in the 2.7V to 6.0V range. Typical efficiencies are greater than 85. Typical quiescent supply current is 25µA (1µA in shutdown).

The MAX856–MAX859 combine ultra-low quiescent supply current and high efficiency to give maximum battery life. An internal MOSFET power transistor permits high switching frequencies. This benefit, combined with internally set peak inductor current limits, permits the use of small, low-cost inductors. The MAX856/MAX857 have a 500mA peak inductor current limit. The MAX858/MAX859 have a 125mA peak inductor current limit.

Features

♦ 0.8V to 6.0V Input Supply Voltage

♦ 0.8V Typ Start-Up Supply Voltage

♦ 85 Efficiency at 100mA

♦ 25µA Quiescent Current

♦ 1µA Shutdown Mode

♦ 125mA and 500mA Switch-Current Limits Permit

   Use of Low-Cost Inductors

♦ Up to 500kHz Switching Frequency

♦ ±1.5 Reference Tolerance Over Temperature

♦ Low-Battery Detector (LBI/LBO)

♦ 8-Pin SO and µMAX Packages

Applications

   3.3V to 5V Step-Up Conversion

   Palmtop Computers

   Portable Data-Collection Equipment

   Personal Data Communicators/Computers

   Medical Instrumentation

   2-Cell & 3-Cell Battery-Operated Equipment

   Glucose Meters