Simplified Block Diagram
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- Ultra-High Efficiency
- Accurate Current-Limit Option
- Quick-PWM with 100ns Load-Step Response
- 1% VOUT Accuracy Over Line and Load
- 1.8V/2.5V Fixed or 1V to 5.5V Adjustable Output Range
- 2V to 28V Battery Input Range
- 200/300/450/600kHz Switching Frequency
- Adjustable Overvoltage Protection
- Adjustable Undervoltage Protection
- 1.7ms Digital Soft-Start
- Drives Large Synchronous-Rectifier FETs
- 2V ±1% Reference Output
- Power-Good Window Comparator
- 1.8V and 2.5V Supplies
- Chipset/RAM Supplies as Low as 1V
- CPU Core Supplies
- Notebook Computers
Maxim's proprietary Quick-PWM quick-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. Efficiency is enhanced by an ability to drive very large synchronous-rectifier MOSFETs. Accurate current sensing to ensure reliable overload protection is available using an external current-sense resistor in series with the synchronous rectifier. Alternatively, the synchronous rectifier itself can be used for less accurate current sensing at the lowest possible power dissipation.
Single-stage buck conversion allows the MAX1844 to directly step down high-voltage batteries for the highest possible efficiency. Alternatively, two-stage conversion (stepping down the 5V system supply instead of the battery) at a higher switching frequency allows the minimum possible physical size.
The MAX1844 is intended for CPU core, chipset, DRAM, or other low-voltage supplies as low as 1V. It is available in 20-pin QSOP, and QFN packages and includes both adjustable overvoltage and undervoltage protection.
For a dual step-down PWM controller with accurate current limit, refer to the MAX1845. The MAX1714/ MAX1715 single/dual PWM controllers are similar to the MAX1844/MAX1845 but do not use current-sense resistors.