Datasheet

ADSP-2186
–27–
REV. B
OUTPUT DRIVE CURRENTS
Figure 22 shows typical I-V characteristics for the output drivers
of the ADSP-2186. The curves represent the current drive
capability of the output drivers as a function of output voltage.
SOURCE VOLTAGE – Volts
60
40
–60
061
SOURCE CURRENT – mA
2345
20
0
–20
–40
–80
5.5V, –40ⴗC
V
OH
5.0V, +25ⴗC
4.5V, +85ⴗC
4.5V, +85ⴗC
5.0V, +25ⴗC
5.5V, –40ⴗC
V
OL
Figure 22. Typical Drive Currents
POWER DISSIPATION
To determine total power dissipation in a specific application,
the following equation should be applied for each output:
C × V
DD
2
× 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
= 5.0 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 ⴛ C ⴛ V
DD
2
ⴛf
Address 7 × 10 pF × 5
2
V × 20 MHz = 35 mW
Data Output, WR 9 × 10 pF × 5
2
V × 20 MHz = 45 mW
RD 1 × 10 pF × 5
2
V × 20 MHz = 5 mW
CLKOUT, DMS 2 × 10 pF × 5
2
V × 40 MHz = 20 mW
105 mW
Total power dissipation for this example is PINT + 105 mW.
80
20
0
60
40
POWER (P
IDLE
n) – mW
1/tcyc – MHz
33.33 40
IDLE (16)
IDLE (128)
IDLE
POWER, IDLE n MODES
2
0
80
40
20
60
POWER (P
IDLE
) – mW
1/tcyc – MHz
33.33 40
V
DD
= 5.5V
V
DD
= 5.0V
V
DD
= 4.5V
POWER, IDLE
1,2,4
100
1/tcyc – MHz
4033.33
100
300
200
500
400
POWER (P
INT
) – mW
0
V
DD
= 5.5V
V
DD
= 5.0V
V
DD
= 4.5V
2186 POWER, INTERNAL
1,2,3
385mW
300mW
225mW
330mW
250mW
180mW
91.5mW
70.5mW
52mW
82mW
62mW
45mW
70.5mW
36.6mW
34.3mW
62mW
34.7mW
32.8mW
POWER REFLECTS DEVICE OPERATING WITH NO OUTPUT LOADS.
TYPICAL POWER DISSIPATION AT 5.0V V
DD
AND T
A
= +25ⴗC EXCEPT WHERE SPECIFIED.
I
DD
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.
IDLE REFERS TO ADSP-2186 STATE OF OPERATION DURING EXECUTION OF IDLE
INSTRUCTION. DEASSERTED PINS ARE DRIVEN TO EITHER V
DD
OR GND.
1
4
2
3
VALID FOR ALL TEMPERATURE GRADES.
Figure 23. Power vs. Frequency