US3004,US3005
TYPICAL APPLICATION
Pentium with AGP
L1
L2
Q1
5V
Vout 3
R16
R17
C16
C5
R1
C7
R4
Q2
C13
C3
C4
C10
R2
R3
R12
R13
3.3V
12V
Q3
C6
C9
C11
12
V12
5
V5
8
9
HDrv
7
CS-
11
10
Gnd
14
Vfb3
R18
R7
R8
CS+
LDrv
R11
1 Ct
Lin1 2
C15
C1
US3004
13 SS
Vfb1 3
Lin2
20
C2
D4
15
D3
16
D2
17
D1
18
D0
19
PGd
6
Vfb2
4
Q4
3.3V
C12
R9
VID4
VID3
VID2
VID1
VID0
R14
C14
3.3V
3004app3-1.4
R15
R5
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.
Rev. 1.2
12/8/00
4-8
UNISEM [ UNISEM ]
