Product specifications

Design Guide - VT82C694X Apollo Pro133 with VT82C686A
Preliminary Revision 0.5, November 19, 1999 54 Motherboard Design Guidelines
Technologies, Inc.
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Figure 2-47 shows an application example for the VDDQ Voltage-Switching circuit shown in Figure 2-46. Signal TYPEDET# is
used to determine the VDDQ voltage level (1.5V or 3.3V) for the AGP interface. When TYPEDET# is high, Q1 is always turned
on. The VDDQ output voltage is provided directly by the VCC3 (3.3V). When TYPEDET# is low, the VDDQ output voltage is
1.5V by regulating the VCC3 power source through the SC1105 switching regulator.
5
8
7
CB3
4uH
VDDQ
VCC3
VOSENSE
DH
GNDPGND
NC
+12V
VCC
TYPEDET#
2
1
4
3
6
.1uF
CE3CE2
CE1CB2
1500uF 1500uF
.1uF 1500uF
L1
CGND
CB4
.1uF
+12V
TYPEDET#
(from pin A2 of AGP slot)
SC1105
CGND
Q1
IR3103S
D1
BYV118
Figure 2-47. VDDQ Voltage-Switching Application Circuit
Figure 2-48 shows another application example for the VDDQ Voltage-Switching circuit. When TYPEDET# is low, Q1 is turned
off and a fixed 1.5V output is generated by the CS5257A-1GDP5 linear regulator (U1) to VDDQ. When TYPEDET# is high, Q1
is always turned on. The VDDQ output voltage is provided directly by the VCC3 (3.3V). At the same time, U1 is shut down due
to a higher output voltage (3.3V VDDQ > fixed 1.5V output).
VCC3
D
D
D
D
S
S
S
G
Q1
FDS4410
CS5257A-1GDP5
U2
VIN
CTRL
VOUT
SENSE
ADJ
CB1
.1uF
CE3CE2
1000uF 1000uF
VDDQ
R4
100 1%
R5
20 1%
CT1
10u/16V
CE1
1000uF
5
6
7
8 1
2
3
4
1
2
35
4
VDDQ +12V
R1
4.7K
R3 1K
-TYPEDET
Q2
3904
U1
04
(from pin A2 of AGP slot)
R2
4.7K
VCC
VCC
Figure 2-48. VDDQ Voltage-Switching Application Circuit (II)