Figure 2-47. Vddq Voltage-Switching Application Circuit; Figure 2-48. Vddq Voltage-Switching Application Circuit (Ii) - VIA Technologies Apollo Pro133A Design Manual

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We Connect We Connect
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.
+12V
TYPEDET#
(from pin A2 of AGP slot)
CB4
.1uF
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
CE1
1000uF
VCC
CT1
10u/16V
Preliminary Revision 0.5, November 19, 1999
6
+12V
3
TYPEDET#
2
NC
1
VCC
VOSENSE
CGND 4
PGND
SC1105

Figure 2-47. VDDQ Voltage-Switching Application Circuit

Q1
8 1
D S
7 2
D S
6 3
D S
5 4
D G
FDS4410
U2
5
VIN VOUT
SENSE
4
CTRL
CS5257A-1GDP5

Figure 2-48. VDDQ Voltage-Switching Application Circuit (II)

Design Guide - VT82C694X Apollo Pro133 with VT82C686A
Q1
5 IR3103S
DH
7
8 CGND
GND
VDDQ +12V
R1
4.7K
Q2
R3 1K
3904
3
1
R4
100 1%
2
ADJ
CB1
R5
.1uF
20 1%
54
VCC3
CB2 CE1
.1uF 1500uF
L1
4uH
CB3 CE2
D1
BYV118 .1uF 1500uF
VCC
R2
4.7K
U1
-TYPEDET
04
(from pin A2 of AGP slot)
VDDQ
CE2 CE3
1000uF 1000uF
Motherboard Design Guidelines
VDDQ
CE3
1500uF