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19-2187; Rev 1; 9/04




High-Efficiency, Quad Output, Main Power-
Supply Controllers for Notebook Computers
General Description Features




MAX1777/MAX1977/MAX1999
The MAX1777/MAX1977/MAX1999 dual step-down, No Current-Sense Resistor Needed (MAX1999)
switch-mode power-supply (SMPS) controllers generate Accurate Current Sense with Current-Sense
logic-supply voltages in battery-powered systems. The Resistor (MAX1777/MAX1977)
MAX1777/MAX1977/MAX1999 include two pulse-width 1.5% Output Voltage Accuracy
modulation (PWM) controllers, adjustable from 2V to 5.5V 3.3V and 5V 100mA Bootstrapped Linear
or fixed at 5V and 3.3V. These devices feature two linear Regulators
regulators providing 5V and 3.3V always-on outputs. Internal Soft-Start and Soft-Stop Output
Each linear regulator provides up to 100mA output cur- Discharge
rent with automatic linear regulator bootstrapping to the Quick-PWM with 100ns Load Step Response
main SMPS outputs. The MAX1777/MAX1977/MAX1999 3.3V and 5V Fixed or Adjustable Outputs
include on-board power-up sequencing, a power-good (Dual ModeTM)
(PGOOD) output, digital soft-start, and internal soft-stop 4.5V to 24V Input Voltage Range
output discharge that prevents negative voltages on shut-
Ultrasonic Pulse-Skipping Mode (25kHz min)
down.
Power-Good (PGOOD) Signal
Maxim's proprietary Quick-PWMTM quick-response, con-
Overvoltage Protection Enable/Disable
stant on-time PWM control scheme operates without
sense resistors and provides 100ns response to load Ordering Information
transients while maintaining a relatively constant switch-
ing frequency. The unique ultrasonic pulse-skipping 5V/3V
PIN-
mode maintains the switching frequency above 25kHz, PART TEMP RANGE SWITCHING
PACKAGE
which eliminates noise in audio applications. Other fea- FREQUENCY
tures include pulse skipping, which maximizes efficiency MAX1777EEI -40