
Electrical Specifications
Intel PXA255 Processor Electrical, Mechanical, and Thermal Specification
29
To drive the 32.768-kHz crystal pins from an external source
Drive the TEXTAL pin with a digital signal that has a low level near 0 volts and a high level
near VCC. Do not exceed VCC or go below VSS by more than 100 mV. The minimum slew
rate is 1 volt per 1 s. The maximum current sourced by the external clock source when the
clock is at its maximum positive voltage should be approximately 1 mA.
Float the TXTAL pin or drive it complementary to the TEXTAL pin, with the same voltage
level, slew rate, and input current restrictions.
4.6.2
3.6864 MHz Oscillator Specifications
The 3.6864-MHz oscillator is connected between the PXTAL (amplifier input) and PEXTAL
(amplified output).
Table 14 shows the 3.6864-MHz specifications.
To drive the 3.6864-MHz crystal pins from an external source
Drive the PEXTAL pin with a digital signal with a low level near 0 volts and a high level near
VCC. Do not exceed VCC or go below VSS by more than 100 mV. The minimum slew rate is
1 volt / 100 ns. The maximum current sourced by the external clock source when the clock is
at its maximum positive voltage should be approximately 1 mA.
Float the PXTAL pin or drive it complementary to the PXTAL pin, with the same voltage
level, slew rate, and input current restrictions. If floated, some degree of noise susceptibility
will be introduced in the system; therefore, it is not recommended.
Table 14. 3.6864-MHz Oscillator Specifications
Symbol
Description
Min
Typical
Max
Units
Crystal Specifications - Typical is FOX HC49S
FXP
Crystal Frequency, PXTAL/PEXTAL
—
3.6864
—
MHz
ESR
Equivalent series resistance, PXTAL/PEXTAL
50
-
300
P
Drive Level
—
100
uW
Amplifier Specifications
VIH_X
Input High Voltage, PXTAL
0.8*VCC
VCC
V
VIL_X
Input Low Voltage, PXTAL
VSS
0.2*VCC
V
IIN_XP
Input Leakage, PXTAL
10
A
CIN_XP
Input Capacitance, PXTAL/PEXTAL
40
50
pF
tS_XP
Stabilization Time
17.8
67.8
ms
Board Specifications
RP_XP
Parasitic Resistance, PXTAL/PEXTAL to any node
20
M
CP_XP
Parasitic Capacitance, PXTAL/PEXTAL, total
5
pF
COP_XP
Parasitic Shunt Capacitance, PXTAL to PEXTAL
0.4
pF