ADSP-2181
(C × VDD 2 × f ) is calculated for each output:
O UTP UT D RIVE CURRENTS
Figure 19 shows typical I-V characteristics for the output drivers
of the ADSP-2181. T he curves represent the current drive
capability of the output drivers as a function of output voltage.
# of
P ins × C
2
× VD D
× f
× 10 pF × 52
V
× 33.3 MHz
× 16.67 MHz
× 16.67 MHz
× 33.3 MHz
=
=
=
=
66.6 mW
37.5 mW
4.2 mW
8.3 mW
116.6 mW
120
Address, DMS
Data Output, WR
RD
8
9
1
1
× 10 pF × 52
× 10 pF × 52
× 10 pF × 52
V
V
V
100
80
60
5.5V, –40؇C
5.0V, +25؇C
CLKOUT
40
4.5V, +85؇C
20
T otal power dissipation for this example is PINT + 116.6 mW.
0
4.5V, +85؇C
1, 3, 4
2181 POWER, INTERNAL
–20
–40
–60
–80
570
5.5V, –40؇C
5.0V, +25؇C
550mW
520
V
= 5.5V
DD
470
420
0
1
2
3
4
5
6
SOURCE VOLTAGE – Volts
425mW
330mW
410mW
V
= 5.0V
Figure 19. Typical Drive Currents
DD
370
320
P O WER D ISSIP ATIO N
T o determine total power dissipation in a specific application,
the following equation should be applied for each output:
325mW
250mW
V
= 4.5V
DD
270
220
2
C × VDD × f
28
30
32
34
36
38
40
42
1/t – MHz
CK
C = load capacitance, f = output switching frequency.
1, 2, 3
POWER, IDLE
Exam ple:
100
90
In an application where external data memory is used and no
other outputs are active, power dissipation is calculated as
follows:
V
= 5.5V
= 5.0V
= 4.5V
DD
95mW
75mW
80
70
60
Assumptions:
V
77mW
DD
•
•
External data memory is accessed every cycle with 50% of the
address pins switching.
60mW
45mW
30
V
DD
External data memory writes occur every other cycle with
50% of the data pins switching.
54mW
50
40
30
•
•
Each address and data pin has a 10 pF total load at the pin.
T he application operates at VDD = 5.0 V and tCK = 30 ns.
28
32
34
36
38
40
3
42
1/t – MHz
CK
2
Total Power Dissipation = PINT + (C × VDD × f )
POWER, IDLE n MODES
PINT = internal power dissipation from Power vs. Frequency
graph (Figure 20).
80
75
70
65
60
55
50
45
40
IDLE
75mW
1000
60mW
n
V
V
V
= 5.5V
= 5.0V
= 4.5V
DD
DD
DD
100
10
1
39mW
IDLE (16)
IDLE (128)
35mW
35
30
37mW
40
34mW
30
28
32
34
36
38
42
1/t – MHz
CK
VALID FOR ALL TEMPERATURE GRADES.
1
POWER REFLECTS DEVICE OPERATING WITH NO OUTPUT LOADS.
2
IDLE REFERS TO ADSP-2181 STATE OF OPERATION DURING EXECUTION OF IDLE
INSTRUCTION. DEASSERTED PINS ARE DRIVEN TO EITHER V OR GND.
5
15
25
35
45
55
65
75
85
–5
DD
TEMPERATURE – °C
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.
3
TYPICAL POWER DISSIPATION AT 5.0V V AND 25؇C EXCEPT WHERE SPECIFIED.
DD
4
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.
DD
Figure 21. Power vs. Frequency
Figure 20. Power-Down Supply Current (Typical)
REV. D
–25–
ADI [ ADI ]
