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ADSP-2186L
–26–
REV. A
POWER DISSIPATION
To determine total power dissipation in a specific application,
the following equation should be applied for each output:
C
×
V
DD2
×
f
C
= load capacitance,
f
= output switching frequency.
Example
In an application where external data memory is used and no
other outputs are active, power dissipation is calculated as follows:
Assumptions
External data memory is accessed every cycle with 50% of the
address pins switching.
External data memory writes occur every other cycle with
50% of the data pins switching.
Each address and data pin has a 10 pF total load at the pin.
The application operates at V
DD
= 3.3 V and t
CK
= 30 ns.
Total Power Dissipation = P
INT
+ (
C
×
V
DD
2
×
f
)
P
INT
= internal power dissipation from Power vs. Frequency
graph (Figure 23).
(
C
×
V
DD
2
×
f
) is calculated for each output:
# of
Pins
×
C
×
V
DD2
×
f
Address,
DMS
Data Output,
WR
RD
CLKOUT
8
9
1
1
×
10 pF
×
3.3
2
V
×
33.3 MHz
×
10 pF
×
3.3
2
V
×
16.67 MHz =
×
10 pF
×
3.3
2
V
×
16.67 MHz =
×
10 pF
×
3.3
2
V
×
33.3 MHz
=
29.0 mW
16.3 mW
1.8 mW
3.6 mW
50.7 mW
=
Total power dissipation for this example is PINT + 50.7 mW.
Output Drive Currents
Figure 22 shows typical I-V characteristics for the output drivers
of the ADSP-2186L. The curves represent the current drive
capability of the output drivers as a function of output voltage.
SOURCE VOLTAGE
–
V
0
3.5
0.5
1
1.5
2
2.5
3
80
–
80
S
–
60
0
–
20
–
40
–
60
40
20
V
DD
= 3.3V @ +25 C
V
DD
= 3.6V @
–
40 C
V
DD
= 3.0V @ +85 C
V
DD
= 3.3V @ +25 C
V
DD
= 3.0V @ +85 C
V
DD
= 3.6V @
–
40 C
V
OH
V
OL
Figure 22. Typical Output Driver Characteristics
VALID FOR ALL TEMPERATURE GRADES.
1
POWER REFLECTS DEVICE OPERATING WITH NO OUTPUT LOADS.
2
TYPICAL POWER DISSIPATION AT 3.3V V
DD
AND T
A
= 25
°
C EXCEPT WHERE SPECIFIED.
3
I
MEASUREMENT TAKEN WITH ALL INSTRUCTIONS EXECUTING FROM INTERNAL
MEMORY. 50% OF THE INSTRUCTIONS ARE MULTIFUNCTION (TYPES 1, 4, 5, 12, 13, 14)
30% ARE TYPE 2 AND TYPE 6, AND 20% ARE IDLE INSTRUCTIONS.
4
IDLE REFERS TO ADSP-2186L STATE OF OPERATION DURING EXECUTION OF IDLE
INSTRUCTION. DEASSERTED PINS ARE DRIVEN TO EITHER V
DD
OR GND.
28
8
26
24
16
14
12
10
22
20
18
P
I
n
)
–
1/t
CK
–
MHz
30
32
34
36
38
40
42
22mW
12mW
13mW
28mW
IDLE (16)
IDLE (128)
IDLE
POWER, IDLE
n
MODES
2
30
32
16
36
26
24
22
20
34
32
28
30
18
P
I
)
–
1/t
CK
–
MHz
42
30
32
34
36
38
40
27mW
35mW
V
DD
= 3.6V
22mW
28mW
V
DD
= 3.3V
19mW
22mW
V
DD
= 3.0V
POWER, IDLE
1, 2, 4
1/t
CK
–
MHz
42
30
32
34
36
38
40
180
80
170
120
110
100
90
160
150
130
140
126mW
102mW
83mW
139mW
113mW
V
DD
= 3.6V
V
DD
= 3.3V
V
DD
= 3.0V
2186L POWER, INTERNAL
1, 2, 3
169mW
P
I
)
–
10mW
9mW
Figure 23. Power vs. Frequency