Power and Clocking

8.7.4I/O 3.3 V Power

A simple LDO linear regulator supplies the 3.3V rail. The Analog Devices ADP3335 is chosen for its very low drop-out – 200 mV at 500 mA and 110 mV at 200 mA. So typically, the input cut-off voltage for this device is about 3.3 V + 0.11 V = 3.41 V. The power is drawn directly from the Li+ battery. For a 3.6 V battery, this device has a 82% efficiency. There are four zones of operation for the Li+ battery:

4.1 – 3.8 V zone 10% of the time;

3.7 – 3.6 V zone at 70% of the time;

3.5 – 3.4 V at 10% of the time; and

3.4 – 3.1 V at 10% of the time.

The ADP3335 operates in zone 1,2, 3, and cutoffs in zone 4.

The overall efficiency is:

0.1(3.3/4.0) + 0.7(3.3/3.6) + 0.1(3.3/3.4) = 0.0825 + 0.642 + 0.097 = 0.82

To access the energy in zone 4 use the second LDO linear regulator in a parallel configuration with the ADP3335 and set it to output 3.2 V. Input to this regulator is 5.5 V from the boost converter. When the battery voltage drops below 3.5 V, the ADP3335 drops-out and the second regulator takes over.

8.7.5Peripheral 5.5 V Power

The example form factor reference design provides a 5.5 V rail to supply power to LCD, Audio amplifier and Radio modules. An LT1308A boost converter is used. This device supplies up to 1 A at 5.5 V while operating at 600 kHz with up to 90% efficiency at rated load and 3.6 V input.

In addition, a low battery voltage detect circuit has an open-drain output. The detect voltage is set at 3.45 V by a resistor divider circuit. When the battery drops below 3.45 V the output transitions to a logic low. This output signal is used as a processor interrupt.

PXA250 and PXA210 Applications Processors Design Guide

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Intel PXA250 and PXA210 manual 4 I/O 3.3 V Power, Peripheral 5.5 V Power

PXA250 and PXA210 specifications

The Intel PXA250 and PXA210 processors, part of the Intel XScale architecture, were introduced in the early 2000s, targeting mobile and embedded applications. They are known for their low power consumption, high performance, and advanced multimedia capabilities, making them suitable for a wide range of devices, including PDAs, smartphones, and other portable computing devices.

The PXA250, which operates at clock speeds ranging from 400 MHz to 624 MHz, features a superscalar architecture that allows it to issue multiple instructions per clock cycle. This enhances the overall performance for demanding applications while maintaining low power usage. It supports a variety of peripheral interfaces, including USB, Ethernet, and various memory types, which contributes to its versatility in different product designs.

One of the key technologies in the PXA250 is the integrated Intel Smart Repeat Technology, which optimizes data processing, thereby reducing the amount of power consumed during operation. This feature is particularly important for battery-powered devices, as it extends the overall battery life, allowing for longer usage times in mobile environments. Additionally, the PXA250 includes a dedicated graphics acceleration unit, which enables enhanced graphics and multimedia performance suited to modern applications at the time.

In contrast, the PXA210 is a more entry-level processor, aimed at cost-sensitive applications. Operating at lower clock speeds, typically around 200 MHz to 400 MHz, it forgoes some of the advanced performance features of the PXA250 while still offering a good balance of performance and power efficiency. The PXA210 is less complex, making it suitable for simpler devices that do not require the extensive capabilities of the PXA250.

Both processors utilize the Intel XScale architecture, which is based on the ARM instruction set. They are built on a 0.13-micron process technology, enabling higher density and lower power consumption compared to their predecessors. With integrated memory controllers and bus interfaces, they facilitate efficient data handling and connectivity options.

In summary, both the Intel PXA250 and PXA210 processors played a crucial role in the evolution of mobile computing by providing powerful processing capabilities with energy efficiency. Their features and technologies enabled device manufacturers to create innovative products that catered to the growing demand for portable devices during that era.