Datasheet

ADSP-2181
–25–
REV. D
OUTPUT DRIVE CURRENTS
Figure 19 shows typical I-V characteristics for the output drivers
of the ADSP-2181. The curves represent the current drive
capability of the output drivers as a function of output voltage.
SOURCE VOLTAGE – Volts
SOURCE CURRENT – mA
120
–80
01 6
2345
100
0
–20
–40
–60
80
60
20
40
5.5V, –408C
5.0V, +258C
4.5V, +858C
4.5V, +858C
5.0V, +258C
5.5V, –408C
Figure 19. 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 20).
TEMPERATURE – °C
1000
1
100
10
CURRENT (LOG SCALE) – mA
58515 25 35 45 55 65 75
–5
V
DD
= 5.5V
V
DD
= 5.0V
V
DD
= 4.5V
NOTES:
1. REFLECTS ADSP-2181 OPERATION IN LOWEST POWER MODE.
(SEE “SYSTEM INTERFACE" CHAPTER OF THE
ADSP-2100 FAMILY
USER'S MANUAL, THIRD EDITION, FOR DETAILS.)
2. CURRENT REFLECTS DEVICE OPERATING WITH NO OUTPUT LOADS.
Figure 20. Power-Down Supply Current (Typical)
(C × V
DD
2
× f ) is calculated for each output:
# of
Pins × C × V
DD
2
× f
Address, DMS 8 × 10 pF × 5
2
V × 33.3 MHz = 66.6 mW
Data Output, WR 9 × 10 pF × 5
2
V × 16.67 MHz = 37.5 mW
RD 1 × 10 pF × 5
2
V × 16.67 MHz = 4.2 mW
CLKOUT 1 × 10 pF × 5
2
V × 33.3 MHz = 8.3 mW
116.6 mW
Total power dissipation for this example is P
INT
+ 116.6 mW.
1/t
CK
– MHz
POWER (P
INT
) – mW
220
30 32 42
34 36 38 40
420
370
320
270
570
470
520
2181 POWER, INTERNAL
1, 3, 4
V
DD
= 5.5V
V
DD
= 5.0V
V
DD
= 4.5V
410mW
325mW
250mW
550mW
425mW
330mW
28
POWER (P
IDLE
) – mW
1/t
CK
– MHz
100
40
30 32 4234 36 38 40
70
60
50
90
80
30
POWER, IDLE
1, 2, 3
V
DD
= 5.5V
V
DD
= 5.0V
V
DD
= 4.5V
77mW
60mW
45mW
95mW
75mW
54mW
28
1/t
CK
– MHz
POWER (P
IDLE
n
) – mW
80
30
30 32 42
34 36 38 40
75
50
45
40
35
70
65
55
60
POWER, IDLE n MODES
3
IDLE
IDLE (16)
IDLE (128)
60mW
35mW
34mW
39mW
37mW
75mW
28
VALID FOR ALL TEMPERATURE GRADES.
4
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
TYPICAL POWER DISSIPATION AT 5.0V V
DD
AND 258C EXCEPT WHERE SPECIFIED.
2
IDLE REFERS TO ADSP-2181 STATE OF OPERATION DURING EXECUTION OF IDLE
1
POWER REFLECTS DEVICE OPERATING WITH NO OUTPUT LOADS.
INSTRUCTION. DEASSERTED PINS ARE DRIVEN TO EITHER V
DD
OR GND.
Figure 21. Power vs. Frequency