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For an application in which external data memory is used in a 32-bit single bus mode and no other
outputs are active, the core runs at 200 MHz, the CPM runs at 100 MHz and the SIU runs at 50 MHz,
power dissipation is calculated as follows:
Assumptions:
• External data memory is accessed every second cycle with 10% of address pins switching.
• External data memory writes occurs once every eight cycles with 50% of data pins switching.
• Each address and data pin has a 30 pF total load at the pin.
• The application operates at
Since the address pins switch once at every second cycle, the address pins frequency is a quarter of the
bus frequency (that is, 25 MHz).
For the same reason the data pins frequency is 3.125 MHz.
# of pins
Pins
switching
Address
Data, HRD, HRW
34
CLKOUT
Total P
I/O
Calculating internal power:
P
(200) = ((P
– P
CORE
CORE
) / 100) × 50 + P
P
(50) = ((P
– P
SIU
SIU
LSI
P
(100) = ((P
– P
CPM
CPM
LCP
P
= P
(200) + P
INT
CORE
SIU
P
= P
+ P
= 346 + 67 = 413
D
INT
I/O
Maximum allowed ambient temperature is:
TA = TJ – (PD × θ
)
JA
= 3.3 V.
V
DDH
Table 4-1. Power Dissipation
× C
× 30
4
× 30
× 30
1
)/300) × 200 + P
=((250 – 3) / 300 × 200 + 3=168
LCO
LCO
= ((70 – 2) / 100) × 50 + 2 = 36
LSI
) / 150) × 100 + P
= ((210 – 6) / 150) × 100 + 6 = 142
LCP
(50) + P
(100) =168 + 36 + 142 = 346
CPM
Power Considerations
× V
2
× f × 10
–3
DDH
× 3.3
2
× 12.5 × 10
–3
× 3.3
× 3. 125 × 10
2
–3
× 3.3
2
× 50 × 10
–3
Power in mW
16.25
34.75
16
67
4-3
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