Eurotech Appliances zeus pxa270 Manuel D’Utilisation

 

© 2007 Eurotech Ltd    Issue D 

There are seven on-board supply voltages derived from the +5V supply. They are listed 

in the following table:  

VCC_BATT 

PXA270 Sleep-control subsystem, 

oscillators and real time clock 

3.3V or 3.0V  2.25V 

VCC_CORE  PXA270 core and other internal units 

0.85V-1.55V  91% of 

nominal 

VCC_PLL 

PXA270 Phase-locked loops 

1.3V 

1.18V 

VCC_SRAM  PXA270 Internal SRAM units 

1.1V 

1V

+3V3 

PXA270 I/O, PXA270 internal units, 

on-board 3.3V peripherals 

3.3V 3.05V 

VCC_PER 

PC/104, Audio Amp, CAN Bus 

transceiver, External GPIO pull-ups 

5V 4.63V 

(PC/104 only)

VCC_MODEM Zeus Modem 

5V 

NA 

Reset will be generated if the supplies fall below the thresholds shown in the table. 

VCC_CORE, VCC_PLL and VCC_SRAM rails are controlled by PWR_EN signal of the 

PXA270. They are switched off when PXA270 is in sleep or deep-sleep mode. 

VCC_PER, VCC_MODEM and +3V3 supply rails are controlled by SYS_EN signal of 

the PXA270. They are switched off when PXA270 is in deep-sleep mode. 

VCC_PER rail is also monitored, and reset will be generated to the PC/104 interface if 

the voltage falls below 4.63V. This can also generate an interrupt on pin GPIO20 of the 

PXA270. 

The Linear Technology device LTC3445 is used to provide the power supply for the 

PXA270. It is specifically designed for the PXA27x family of microprocessors.  

The LTC3445 contains a high efficiency buck regulator (VCC_CORE), two LDO 

regulators (VCC_PLL, VCC_SRAM), a PowerPath controller and an I

2

C interface. The 

buck regulator has a 6-bit programmable output range of 0.85V to 1.55V. The buck 

regulator uses either a constant frequency of 1.5MHz, or a spread spectrum switching 

frequency. Using the spread spectrum option gives a lower noise regulated output, as 

well as low noise at the input. In addition, the regulated output voltage slew rate is 

programmable via the Power Management I

2

C interface of the PXA270.