MAX1623

19-1436; Rev 1; 9/99 NUAL KIT MA ATION EET H S A EVALU T WS DA FOLLO 3A, Low-Voltage, Step-Down Regulator with Synchronous Rectification and Internal Switches General Description The MAX1623 switch-mode buck regulator with synchronous rectification provides local CPU and bus-termination power in notebook and desktop computers. An internal 55mΩ (typ), 3A PMOS power switch and 60m Ω (typ), 3A NMOS synchronous-rectifier switch deliver continuous load currents up to 3A from a 5V supply with 95% typical efficiency. Output accuracy is ±1%, including line and load regulation. The MAX1623 features constant-off-time, current-mode pulse-width-modulation (PWM) control with switching frequencies as high as 350kHz. An external resistor at the TOFF pin sets the off-time, allowing optimum design flexibility in terms of switching frequency, output switching noise, and inductor size. This device is available in a space-saving 20-pin SSOP package. ____________________________Features o ±1% Output Accuracy, Including Line and Load Regulation o 94% Efficiency o Internal Switches 55mΩ PMOS Power Switch 60mΩ NMOS Synchronous-Rectifier Switch o Guaranteed 3A Load Capability o Minimal External Components o Pin-Selectable Fixed 3.3V, 2.5V, or Adjustable (1.1V to 3.8V) Output Voltage o +4.5V to +5.5V Input Voltage Range o 400µA (typ) Supply Current o <1µA Shutdown Supply Current o Constant-Off-Time PWM Operation o Switching Frequencies Up to 350kHz o Idle Mode™ Operation at Light Loads o Thermal Sh...