General Description

The MAX1533A/MAX1537A are dual step-down, switch mode power-supply (SMPS) controllers with synchronous rectification, intended for main 5V/3.3V power generation in battery-powered systems. Fixed-frequency operation with optimal interleaving minimizes input ripple current from the lowest input voltages up to the 26V maximum input. Optimal 40/60 interleaving allows the input voltage to go down to 8.3V before duty-cycle overlap occurs, compared to 180° out-of-phase regulators where the duty-cycle overlap occurs when the input drops below 10V. Output current sensing provides accurate current limit using a sense resistor. Alternatively, power dissipation can be reduced using lossless inductor current sensing

Features

♦ Fixed-Frequency, Current-Mode Control

♦ 40/60 Optimal Interleaving

♦ Accurate Differential Current-Sense Inputs

♦ Internal 5V and 3.3V Linear Regulators with 100mA Load Capability

♦ Auxiliary 12V or Adjustable 150mA Linear Regulator (MAX1537A Only)

♦ Dual Mode™ Feedback—3.3V/5V Fixed or Adjustable Output (Dual Mode) Voltages

♦ 200kHz/300kHz/500kHz Switching Frequency

♦ Versatile Power-Up Sequencing

♦ Adjustable Overvoltage and Undervoltage Protection

♦ 6V to 26V Input Range

♦ 2V ±0.75 Reference Output

♦ Power-Good Output

♦ Soft-Shutdown

♦ 5µA (typ) Shutdown Current

Applications

2 to 4 Li+ Cells Battery-Powered Devices

Notebook and Subnotebook Computers

PDAs and Mobile Communicators