General Description

The MAX1830/MAX1831 constant-off-time, pulse-width-modulated (PWM) step-down DC-DC converters are ideal for use in 5V and 3.3V to low-voltage conversion necessary in notebook and subnotebook computers. These devices feature internal synchronous rectification for high efficiency and reduced component count. They require no external Schottky diode. The internal 45mΩ PMOS power switch and 55mΩ NMOS synchronous-rectifier switch easily deliver continuous load currents up to 3A. The MAX1830 produces preset +2.5V, +1.8V, or +1.5V output voltage or an adjustable output from +1.1V to VIN. The MAX1831 produces preset +3.3V, +2.5V, and +1.5V output voltages and an adjustable output from +1.1V to VIN. They achieve efficiencies as high as 94.

The MAX1830/MAX1831 use a unique current-mode, constant-off-time, PWM control scheme, which includes Idle Mode™ to maintain high efficiency during light load operation. The programmable constant-off-time architecture sets switching frequencies up to 1MHz, allowing the user to optimize performance trade offs between efficiency, output switching noise, component size, and cost. Both devices are designed for continuous output currents up to 3A, an internal digital soft-start to limit surge currents during startup, a 100 duty cycle mode for low-dropout operation, and a low-power shutdown mode that disconnects the input from the output and reduces supply current below 1µA.The MAX1830/MAX1831 are available in 16-pin QSOP packages.

For similar devices that provide continuous output currents of 1A to 3A, refer to the MAX1644, MAX1623, and MAX1742/MAX1842/MAX1843 data sheets.

Features

♦ ±1.5 Output Accuracy

♦ 94 Efficiency

♦ Internal PMOS/NMOS Switches

45mΩ/55mΩ On-Resistance at VIN = +4.5V

50mΩ/55mΩ On-Resistance at VIN = +3V

♦ Output Voltages

+3.3V, +2.5V, or +1.5V Pin Selectable (MAX1831)

+2.5V, +1.8V, or +1.5V Pin Selectable (MAX1830)

+1.1V to VIN Adjustable (Both Devices)

♦ +3V to +5.5V Input Voltage Range

♦ 750µA (max) Operating Supply Current

♦ <1µA Shutdown Supply Current

♦ Programmable Constant-Off-Time Operation

♦ Up to 1MHz Switching Frequency

♦ Idle Mode Operation at Light Loads

♦ Thermal Shutdown

♦ Internal Digital Soft-Start Inrush Current Limiting

♦ 100 Duty Cycle During Low-Dropout Operation

♦ Output Short-Circuit Protection

♦ 16-Pin QSOP Package

Applications

5V or 3.3V to Low-Voltage Conversion

CPU I/O Supplies

Chipset Supplies

Notebook and Subnotebook Computers