Single Gmch And Ich4-M Voltage Generation / Separate Divider Circuit For Vswing/Vref; Figure 89. Ich4-M And Gmch Locally Generated Reference Voltage Divider Circuit; Figure 90. Shared Gmch & Ich4-M Reference Voltage With Separate Voltage Divider Circuit For Vswing And Vref; Table 83. Recommended Resistor Values For Separate Hivref And Hi_Vswing Divider - Intel 855GM Design Manual

Hub Interface

Figure 89. ICH4-M and GMCH Locally Generated Reference Voltage Divider Circuit

10.3.3. Single GMCH and ICH4-M Voltage Generation / Separate
Divider Circuit for VSWING/VREF
This section describes the option to use one voltage divider circuit for VREF, shared by both ICH4-M
and GMCH, while using another voltage divider circuit for VSWING. This allows for tuning the two
reference voltages independently. The reference voltage for both HIVREF and HI_VSWING must meet
the voltage specification in Table 81. Normal care needs to be taken to minimize crosstalk to other
signals (< 10-15 mV).
Figure 90. Shared GMCH & ICH4-M Reference Voltage with Separate Voltage Divider Circuit for
VSWING and VREF
Table 83. Recommended Resistor Values for Separate HIVREF and HI_VSWING Divider Circuits
Signal
HIVREF
(350mV)
HI_VSWING
(800mV)
192
VCCHI
R1
C5
C1
R2
C6
C3
R3
V HI=1.5V
CC
R4
PVSWING
HLVREF
GMCH
R5
C6
C5
Recommended Resistor Values
R4 = 43.2 Ω ± 1%
R5 = 49.9 Ω ± 1%,
R6 = 78.7 Ω ± 1%
R7 = 24.2 Ω ± 1%,
VCCHI
R1
PSWING
C1
R2
GMCH
HLVREF
C3
R3
R6
HI_VSWING
Intel
HIREF
ICH4
R7
C4
C3 C1 C2
VCCHI
VCCHI=1.5 V
VCCHI=1.5 V
®
Intel 855GM/855GME Chipset Platform Design Guide
HI_VSWING
C2
ICH4
HIREF
C4
R4 = 43.2 Ω ± 1%,
R5 = 49.9 Ω ± 1%,
R6 = 78.7 Ω ± 1%,
R7 = 24.2 Ω ± 1%
C1 and C3 = 0.1 µF
(near divider)
C2, C4, C5, C6 =
®
0.01µF (near
component)
Capacitor value
C3 = 0.1 µF (near divider)
C2, C5 = 0.01 µF (near component)
C1 = 0.1 µF (near divider)
C4, C6 = 0.01 µF (near component)
R