ADSP-21065 Analog Devices, ADSP-21065 Datasheet - Page 38

• Manufacturer Part Number: ADSP-21065
• Description: DSP Microcomputer
• Manufacturer: Analog Devices

ADSP-21065L
POWER DISSIPATION
Total power dissipation has two components: one due to inter-
nal circuitry and one due to the switching of external output
drivers. Internal power dissipation depends on the sequence in
which instructions execute and the data operands involved. See
I
power dissipation is calculated this way:
The external component of total power dissipation is caused by
the switching of output pins. Its magnitude depends on:
– the number of output pins that switch during each cycle (O)
– the maximum frequency at which the pins can switch (f)
– the load capacitance of the pins (C)
– the voltage swing of the pins (V
The external component is calculated using:
The load capacitance should include the processor’s package
capacitance (C
high and then back low. Address and data pins can drive high
and low at a maximum rate of 1/t
mode.
Example:
Estimate P
– a system with one bank of external memory (32-bit)
– two 1M × 16 SDRAM chips, each with a control signal load
– external data writes occur in burst mode, two every 1/t
– the external SDRAM clock rate is 60 MHz (2/t
The P
drive:
Pin
Type
Address
MS
SDWE
Data
SDRAM CLK 1
DDIN
of 3 pF and a data signal load of 4 pF
cycles, a potential frequency of 1/t
pin switching
0
calculation in Electrical Characteristics section. Internal
EXT
equation is calculated for each class of pins that can
EXT
Table V. External Power Calculations
# of
Pins Switching
11
1
1
32
IN
with the following assumptions:
). The frequency f includes driving the load
%
50
0
0
50
–
P
EXT
P
INT
= O × C × V
= I
× 10.7
× 10.7
× 10.7
× 7.7
× 10.7
DDIN
C
CK
DD
× V
).
while in SDRAM burst
CK
× 30 MHz × 10.9 V = 0.019 W
—
—
× 30 MHz × 10.9 V = 0.042 W
× 30 MHz × 10.9 V = 0.007 W
DD
f
DD
cycles/s. Assume 50%
2
× f
× 10.9 V = 0.000 W
× 10.9 V = 0.000 W
V
CK
DD
P
).
2
EXT
= 0.068 W
= P
CK
EXT
A typical power consumption can now be calculated for these
conditions by adding a typical internal power dissipation. (I
see calculation in Electrical Characteristics section):
Note that the conditions causing a worst-case P
those causing a worst-case P
while 100% of the output pins are switching from all ones (1s)
to all zeros (0s). Note also that it is not common for an appli-
cation to have 100% or even 50% of the outputs switching
simultaneously.
ENVIRONMENTAL CONDITIONS
Thermal Characteristics
The ADSP-21065L is offered in a 208-lead MQFP and a 196-
ball Mini-BGA package.
The ADSP-21065L is specified for a case temperature (T
To ensure that T
used.
T
PD =
θ
θ
Airflow
(Linear Ft./Min.)
θ
(Linear Ft./Min.)
θ
JC
JC
CA
CA
CASE
=
=
(°C/W)
(°C/W)
Table VI. Thermal Characteristics (208-Lead MQFP)
= Case temperature (measured on top surface of package)
Power Dissipation in W (this value depends upon the
specific application; a method for calculating PD is
shown under Power Dissipation)
7.1°C/W for 208-lead MQFP
5.1°C/W for 196-ball Mini-BGA
Table VII. 196-Ball Mini-BGA
P
CASE
TOTAL
T
CASE
is not exceeded, an air flow source may be
= P
0
24
0
38
= T
EXT
INT
AMB
. Maximum P
+ (I
+ (PD × θ
100
20
DDIN
× V
CA
200
19
200
29
DD
)
INT
)
EXT
cannot occur
differ from
400
17
CASE
DDIN
600
13
400
23
)
.