US3007
Note: It is better to place the 1.5V linear regulator com-
ponents close to the 3007 and then run a trace from the
output of the regulator to the load. However, if this is not
possible then the trace from the linear drive output pin,
pin 18 must be run away from any high frequency
data signals.
It is critical, to place high frequency ceramic ca-
pacitors close to the clock chip and termination
resistors to provide local bypassing.
9) Place R12 and C10 close to pin 23 and R9 and C5
close to pin 9.
10) Place C9 close to pin 12
Component connections:
Note : It is extremely important that no data bus
should be passing through the switching regulator
section specifically close to the fast transition nodes
such as PWM drives or the inductor voltage.
Using the 4 layer board, dedicate on layer to GND, an-
other layer as the power layer for the 5V, 3.3V, Vcore,
1.5V and if it is possible for the 2.5V.
Connect all grounds to the ground plane using di-
rect vias to the ground plane.
Use large low inductance/low impedance plane to con-
nect the following connections either using component
side or the solder side.
a) C14 to Q3 Drain and C3 to Q1 drain
b) Q3 Source to Q4 Drain and Q1 Source to D1 cathode
c) Q4 drain to L3 and D1 cathode to L2
d) L3 to the output capacitors, C16 and L2 to the output
capacitors, C1
e) C16 to the load, slot 1
f) Input filter L1 to the C16 and C3
g) C1 to Q2 drain
h) C17 to the Q2 source
I) A minimum of 0.2 inch width trace from the C18 ca-
pacitor to pin 16
Connect the rest of the components using the shortest
connection possible
Rev. 1.8
12/8/00
4-15
UNISEM [ UNISEM ]
