US3004,US3005
TYPICAL APPLICATION
Pentium with AGP
L1
L2
Q1
R16
C5
C13
C3
R2
R3
R1
C7
Q2
R4
R12
R13
C16
C10
R17
5V
Vout 3
3.3V
C4
C6
C9
R18
12
V12
1 Ct
C1
13 SS
C2
D4
15
D3
16
D2
17
D1
18
D0
19
PGd
6
Vfb2
4
5
V5
8
CS+
9
HDrv
7
CS-
11
LDrv
10
Gnd
14
Vfb3
Lin1 2
Q3
C11
R7
R11
C15
Vfb1 3
Lin2
20
R9
R14
3.3V
R5
C14
3004app3-1.4
12V
US3004
Q4
R8
3.3V
C12
VID4
VID3
VID2
VID1
VID0
R15
Power Good
C8
Figure 3- Typical application of US3004 in a Pentium with AGP where the power dissipation of the 3.3V
linear regulator is equally distributed between Q3 and Q4 pass transistors. This equal distribution is
possible by accurately regulating the first regulator using the US3004 linear controller and its internal 1%
reference voltage while the second controller regulates the output of the first regulator from 4.17V to
3.3V, thereby distributing the power dissipation equally.
4-8
Rev. 1.2
12/8/00
UNISEM [ UNISEM ]
