Datasheet

ADSP-2184
–26–
REV. 0
OUTPUT DRIVE CURRENTS
Figure 20 shows typical I-V characteristics for the output drivers
of the ADSP-2184. The curves represent the current drive
capability of the output drivers as a function of output voltage.
SOURCE VOLTAGE – V
0
6010 20 30 40 50
SOURCE CURRENT – mA
60
0
–20
–40
–60
40
20
V
DD
= 5.0V @ +258C
V
DD
= 5.5V @ –408C
V
DD
= 4.5V @ +858C
V
DD
= 5.0V @ +258C
V
DD
= 4.5V @ +858C
V
DD
= 5.5V @ –408C
V
OL
V
OH
Figure 20. 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
= 25 ns.
Total Power Dissipation = P
INT
+ (C × V
DD
2
× f)
P
INT
= internal power dissipation from Power vs. Frequency
graph (Figure 21).
(C × V
DD
2
× f) is calculated for each output:
# of
Pins ⴛ C ⴛ V
DD
2
ⴛf
Address, DMS 8 × 10 pF × 5
2
V × 40 MHz = 80 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 1 × 10 pF × 5
2
V × 40 MHz = 10 mW
140 mW
Total power dissipation for this example is PINT + 40 mW.
VALID FOR ALL TEMPERATURE GRADES.
1
POWER REFLECTS DEVICE OPERATING WITH NO OUTPUT LOADS.
2
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.
3
IDLE REFERS TO ADSP-2184 STATE OF OPERATION DURING EXECUTION OF IDLE
INSTRUCTION. DEASSERTED PINS ARE DRIVEN TO EITHER V
DD
OR GND.
4
TYPICAL POWER DISSIPATION AT 5.0V V
DD
AND T
A
= 258C EXCEPT WHERE SPECIFIED.
65
25
40
35
30
60
55
45
50
POWER (P
IDLE
n
) – mW
62.1mW
34.7mW
32.8mW
34.3mW
36.6mW
70.55mW
IDLE (16)
IDLE (128)
IDLE
POWER, IDLE n MODES
2
70
75
40
95
70
65
60
55
90
85
75
80
50
POWER (P
IDLE
) – mW
82.28mW
91.52mW
V
DD
= 5.5V
62.1mW
70.55mW
V
DD
= 5.0V
44.73mW
51.705mW
V
DD
= 4.5V
POWER, IDLE
1, 2, 4
1/t
CYC
– MHz
33.33 40
175
400
275
250
225
200
375
350
300
325
330mW
250mW
180mW
300mW
225mW
2184 POWER, INTERNAL
1, 2, 3
385mW
POWER (P
INT
) – mW
V
DD
= 5.5V
V
DD
= 5.0V
V
DD
= 4.5V
45
1/t
CYC
– MHz
33.33 40
1/t
CYC
– MHz
33.33
40
150
Figure 21. Power vs. Frequency