MSC8102D Motorola / Freescale Semiconductor, MSC8102D Datasheet - Page 93

• Manufacturer Part Number: MSC8102D
• Description: Quad Core 16-Bit Digital Signal Processor
• Manufacturer: Motorola / Freescale Semiconductor

Chapter 4
Design
Considerations
4.1 Thermal Design Considerations
The average chip-junction temperature
Equation 1: T
where
• T
•
• P
• P
• P
The user should set T
T
4.2 Power Supply Design Considerations
The input voltage must not exceed the I/O supply V
power-on reset. In turn V
during power-on reset. V
during power-on reset. Therefore the recommendation is to use “bootstrap” diodes between the power
rails, as shown in Figure 4-1.
Select the bootstrap diodes such that a nominal V
until the V
diodes are connected in series; each has a forward voltage (V
provide a 2.4 V drop, maintaining 0.9 V on the 1.6 V power line. Once the core/PLL power supply
stabilizes at 1.6 V, the bootstrap diodes will be reverse biased with negligible leakage current. The V
should be effective at the current levels required by the processor. Do not use diodes with a nominal V
that drops too low at high current.
J
is too high, the user should either lower the ambient temperature or the power dissipation of the chip.
A
D
INT
I/O
JA
= P
= ambient temperature C
= package thermal resistance
= power dissipation on output pins in W—user determined
= I
INT
DD
DD
+ P
/V
V
CCSYN
I/O
DD
I/O Power
Core/PLL
J
Supply
in W
= T
Figure 4-1. Bootstrap Diodes for Power-Up Sequencing
in W—chip internal power
A
power supply becomes active. In Figure 4-1, four MUR420 Schottky barrier
and P
A
DD
DDH
+ (P
/V
D
must not exceed V
CCSYN
D
such that T
•
,
junction to ambient
JA
must not exceed V
,
T
)
J
,
J
in C can be obtained from the following:
does not exceed the maximum operating conditions. In case
DD
DD
DDH
/V
/V
CCSYN
CCSYN
MUR420
MUR420
MUR420
MUR420
by more than 2.5 V at any time, including during
,
DDH
C/W
F
by more than 0.4 V at any time, including
by more than 2.6 V at any time, including
is sourced from the V
) of 0.6 V at high currents, so these diodes
3.3 V (V
1.6 V (V
DDH
DDH
DD
/V
power supply
)
CCSYN
)
F
4-1
F