The MAX1761 dual pulse-width-modulation (PWM), step-down controller provides high efficiency, excellent transient response, and high DC output accuracy in an extremely compact circuit topology. These features are essential for stepping down high-voltage batteries to generate low-voltage CPU core, I/O, and chipset RAM supplies in PC board area critical applications, such as notebook computers and smart phones.
Maxim's proprietary Quick-PWM™ quick-response, constant-on-time PWM control scheme handles wide input/output voltage ratios with ease and provides "instant-on" response to load transients while maintaining a relatively constant switching frequency.
The MAX1761 achieves high efficiency at reduced cost by eliminating the current-sense resistor found in traditional current-mode PWMs. Efficiency is further enhanced by its ability to drive large synchronous-rectifier MOSFETs. The MAX1761 employs a complementary MOSFET output stage, which reduces component count by eliminating external bootstrap capacitors and diodes.
Single-stage buck conversion allows this device 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 MAX1761 is intended for CPU core, chipset, DRAM, or other low-voltage supplies. The MAX1761 is available in a 16-pin QSOP package. For applications requiring greater output power, refer to the MAX1715 data sheet. For a single-output version, refer to the MAX1762/MAX1791 data sheet.
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