The MAX1816/MAX1994 are dual step-down controllers for notebook computer applications. BUCK1 is a CPU core regulator with dynamically adjustable output, ultra-fast transient response, high DC accuracy, and high efficiency. BUCK2 is an adjustable step-down regulator for I/O and memory supplies. Both regulators employ Maxim's proprietary Quick-PWM™ control architecture. This fast-response, constant-on-time PWM control scheme handles wide input/output voltage ratios with ease and provides 100ns "instant" on-response to load transients, while maintaining a relatively constant switching frequency. The MAX1816/MAX1994 also have a linear-regulator controller for low-voltage auxiliary power supplies.
The CPU regulator supports "active voltage positioning" to reduce output bulk capacitance and lower power dissipation. A programmable gain amplifier allows the use of lower value sense resistors. Four fixed-gain settings are available (0, 1.5, 2, and 4). A differential remote-sense amplifier is also included to more accurately control the voltage at the load. Accuracy is further enhanced with an internal integrator.
The MAX1816/MAX1994 include a specialized digital interface that makes them suitable for mobile CPU and video processor applications. The power-good (PGOOD) output for the core regulator is forced high during VID transitions, and the LINGOOD output for the linear regulator includes a 1ms (min) turn-on delay.
BUCK1, BUCK2, and the linear regulator feature overvoltage protection (OVP). The detection threshold for BUCK1 is adjusted with an external resistive voltage-divider, while the OVP thresholds for BUCK2 and the linear regulator are fixed. Connecting the OVPSET pin to VCC disables OVP for BUCK1 and BUCK2, but not the linear regulator.
The MAX1816 features an output-voltage adjustment range from 0.6V to 1.75V. Similarly, the MAX1994 is adjustable from 0.925V to 2.0V, using an alternate VID code set. While in suspend mode, the adjustment range is 0.7V to 1.075V for both the MAX1816 and MAX1994. Both parts are available in 48-pin thin QFN packages.
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