MAX1904

19-2224; Rev 3; 12/03 500kHz Multi-Output, Low-Noise Power-Supply Controllers for Notebook Computers 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 Nchannel MOSFET switching. These devices feature a logic-controlled and synchronizable, fixed-frequency, pulse-width modulation (PWM) operating mode. This reduces noise and RF interference in sensitive mobile communications and pen-entry applications. Asserting the SKIP pin enables fixed-frequency mode, for lowest noise under all load conditions. The MAX1901/MAX1902/MAX1904 include two PWM regulators, adjustable from 2.5V to 5.5V with fixed 5.0V and 3.3V modes. All these devices include secondary feedback regulation, and the MAX1902 contains a 12V/120mA linear regul...