Mobile Intel Pentium 4 Processor - M and Intel 845MP/MZ Chipset Platform Design Guide

Mobile Intel
®
Pentium
®
4 Processor-M and Intel
®
845MP/845MZ Chipset Platform
202 Design Guide
R
Table 92. RTC Circuitry
ICH3-M – RTC Circuitry Recommendations
Signal System
Pull-up/Pull-down
Ω
ΩΩ
Ω Notes 9
99
9
CLK_VBIAS Connect 10 MΩ
across to CLK_RTCX1
and 0.047 µF
decoupling cap in
series with 1 k
Ω
10 MΩ
1 k
Ω
Cap for noise immunity
This DC Voltage is a self-adjusted voltage.
Board designers should not manually bias the
voltage level on VBIAS. VBIAS should be at
least 200 mV DC.
CLK_RTCX1,
CLK_RTCX2
Connect a 32.768 kHz
crystal oscillator
across these pins with
a 10 M
Ω resistor and
use 12 pF decoupling
caps at each signal.
10 M
Ω Refer to reference schematics.
RTCX1 may optionally be driven by an external
oscillator, instead of a crystal. These signals
are 1.8 V only, and must not be driven by a 3.3-
V source.
Circuitry is required since the new RTC
oscillator is sensitive to step voltage changes in
VCCRTC and VBIAS. A negative step on power
supply of more than 100 mV will temporarily
shut off the oscillator for hundreds of
milliseconds.
NOTES:
1. Connect supply clock inputs to X1 and X2 of the ICH3-M because other signals are gated off that clock in
suspend modes. However, in this case, the frequency (32.768 kHz) of the clock inputs is not critical; a lower-
cost crystal can be used or a single clock input can be driven into X1 with X2 left as no connect
2. To maintain RTC accuracy, the external capacitor C3 needs to be 0.047 µF and capacitor values C1 and C2
should be chosen to provide the manufacturer’s specified load capacitance (Cload) for the crystal when
combined with the parasitic capacitance of the trace, socket (if used), and package. The following equation
can be used to choose the external capacitance values:
C
load
= [(C
1
+ C
in1
+ C
trace1
)*(C
2
+ C
in2
+ C
trace2
) ]/[ (C
1
+ C
in1
+ C
trace1
+ C
2
+ C
in2
+ C
trace2
)] + C
parasitic
Table 93. LAN Interface
ICH3-M – LAN Interface Recommendations
Signal System
Pull-up/Pull-down
Ω
ΩΩ
Ω Notes 9
99
9
LAN_JCLK No resistor required;
If LAN interface not used, leave unconnected
(NC)
LAN_RXD[2:0] No resistor required, has integrated weak
internal pull-up;
If LAN interface not used, leave unconnected
(NC)
LAN_TXD[2:0],
LAN_RSTSYNC
See notes
Connect to LAN_TXD on Platform LAN Connect
Device.
If LAN interface not used, leave unconnected
(NC).