Consumer products that use Intel XScale microprocessors include third-generation smart cell phones, PDAs, and Internet appliances. To power XScale devices, Maxim designed the MAX1586A and B and the MAX1587. They integrate seven high-performance, low-operating-current power supplies along with supervisory and management functions.
Seven supplies? Indeed, there are three step-down dc-dc outputs, three linear regulators, and a seventh always-on output. The dc-dc converters power I/O, DRAM, and the CPU core. (The I/O supply can be preset to 3.3 or 3.0 V, or adjusted to other values.) The DRAM supply on the 1586A and B is preset for 1.8 or 2.5 V. On the 1587A, it's preset for 3.3 or 2.5 V. On all three parts, the DRAM supply can also be adjusted with external resistors. The CPU core supply is serial-programmed for dynamic voltage management.
That's three supplies. Three more linear-regulated outputs are provided for SRAM, PLL, and USIM supplies. The seventh always-on output is for critical system functions, such as a real-time clock and power boot-up. It's powered either from the main supply when the system is active, or by a backup battery.
Critical power supplies have bypass "sleep" LDOs to minimize battery drain when output current is very low. Other functions include separate on/off control for all dc-dc converters, low-battery and dead-battery detection, a reset and power-OK output, a backup-battery input, and the two-wire serial interface for CPU-supply control.
The MAX1587A fits in a 6- by 6-mm, 40-pin thin QFN, while both versions of the MAX1586 come in 7- by 7-mm, 48-pin thin QFN packages. The parts are screened for -40°C to +85°C. Unit prices start at $5.80 for 1000-piece quantities. An evaluation kit is available.
Maxim Integrated Productswww.maxim.com See associated figure
