General Description

The MAX1901/MAX1902/MAX1904 are buck-topology, step-down, switch-mode, power-supply controllers that generate logic-supply voltages in battery-powered systems. These high-performance, dual/triple-output devices include on-board power-up sequencing, power-good signaling with delay, digital soft-start, secondary winding control, low dropout circuitry, internal frequency-compensation networks, and automatic bootstrapping.

Up to 97 efficiency is achieved through synchronous rectification and Maxim’s proprietary Idle Mode™ control scheme. Efficiency is greater than 80 over a 1000:1 load-current range, which extends battery life in system suspend or standby mode. Excellent dynamic response corrects output load transients within five clock cycles. Strong 1A on-board gate drivers ensure fast external N channel MOSFET switching.

Features

♦ 97 Efficiency

♦ 4.2V to 30V Input Range

♦ 2.5V to 5.5V Dual Adjustable Outputs

♦ Selectable 3.3V and 5V Fixed or Adjustable Outputs (Dual Mode™)

♦ 12V Linear Regulator

♦ Adjustable Secondary Feedback (MAX1901/MAX1904)

♦ 5V/50mA Linear Regulator Output

♦ Precision 2.5V Reference Output

♦ Programmable Power-Up Sequencing

♦ Power-Good (RESET) Output

♦ Output Overvoltage Protection (MAX1901/MAX1902)

♦ Output Undervoltage Shutdown (MAX1901/MAX1902)

♦ 333kHz/500kHz Low-Noise, Fixed-Frequency Operation

♦ Low-Dropout, 98 Duty-Factor Operation

♦ 2.5mW Typical Quiescent Power (12V input, both SMPSs on)

♦ 4µA Typical Shutdown Current

Applications

Notebook and Subnotebook Computers

PDAs and Mobile Communicators

Desktop CPU Local DC-DC Converters