Intel PXA27x Series, User Manual

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44 Intel
®
PXA27x Processor Developer’s Kit - User’s Guide
Intel
®
K3-family flash memory on the main board as the boot source. See Section 2.2.3 for
instructions.
For instructions on programming flash memory, see Section 3.6, “Programming Flash Memory and
Logic Devices” on page 85 .
2.4.3 Clock Sources
By default, the on-card 13 MHz crystal connects to the Intel
®
PXA270 Processor’s PXTAL_IN
input, and the on-card 32.768 kHz crystal connects to the processor’s TXTAL_IN input. This
arrangement uses the Intel
®
PXA270 Processor’s on-chip PLL (phase locked loop).
2.5 Power Management
The Intel
®
PXA27x Processor Developer’s Kit Power Manager Integrated Circuit (Low DropOut)
Card (PMIC card) contains the power regulators needed to supply and manage voltage domains
and optimize power consumption and performance.
2.5.1 Core-Voltage Control and PWR_I
2
C
A serial-digital-to-analog converter (DAC), translates the Intel
®
PXA270 Processor serial
PWR_I2C signals (PWR_SCL and PWR_SDA) into an analog voltage that controls the output of
the regulator. At power-on, and thereafter if not changed by the PWR_I
2
C bus, the control voltage
applied to the regulator defaults to 0, which produces a DC_CORE voltage of 1.417 volts.
Note: Carefully observe the PWR_I2C programming instructions in the Intel
®
PXA27x Processor Family
Developer’s Manual . It is possible to set the output from the regulator to a voltage at which the
Intel
®
PXA270 Processor cannot function (less than approximately 0.7 volts). If shutdown should
occur, cycle the system power and correct the PWR_I2C code that produced the error. This
procedure causes the regulator to produce its default output of 1.417 volts.
Table 12 lists some representative output voltages from the regulator as a function of the binary
input to the DAC. The table lists values in increments of 25, but you can use any integer from 0 to
1023 with the DAC’s digital input. The following equation closely relates the DAC input and the
regulator’s output, where
DACin
is expressed in decimal:
VCC_CORE = 1.5V – (587uV*DAC(input))
Table 12. Programmable DC_CORE Voltages (Sheet 1 of 2)
Binary Input to DAC
(expressed in decimal) DC_CORE
Voltage
Binary Input to DAC
(expressed in decimal) DC_CORE
Voltage
0 1.5 525 1.192
25 1.584 550 1.177
50 1.471 575 1.162
75 1.456 600 1.148
100 1.441 625 1.133