adsp-21mod870-100 Analog Devices, Inc., adsp-21mod870-100 Datasheet - Page 17

• Manufacturer Part Number: adsp-21mod870-100
• Description: Internet Gateway Processor
• Manufacturer: Analog Devices, Inc.

REV. 0
OUTPUT DRIVE CURRENTS
Figure 14 shows typical I-V characteristics for the output driv-
ers of the ADSP-21mod870. The curves represent the current
drive capability of the output drivers as a function of output
voltage.
POWER DISSIPATION
To determine total power dissipation in a specific application,
the following equation should be applied for each output:
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
• External data memory writes occur every other cycle with
• Each address and data pin has a 10 pF total load at the pin.
• The application operates at V
P
graph (Figure 15).
(C
Address, DMS
Data Output, WR 9
RD
CLKOUT
Total power dissipation for this example is P
INT
the address pins switching.
50% of the data pins switching.
= internal power dissipation from Power vs. Frequency
V
DD
–20
–40
–60
–80
Total Power Dissipation = P
2
80
60
40
20
0
0
f) is calculated for each output:
Figure 14. Typical Drive Currents
0.5
# of
Pins
8
1
1
1.0
3.6V, –40
10 pF
10 pF
10 pF
10 pF
C
C V
SOURCE VOLTAGE – V
1.5
°
C
DD
DD
2.0
3.3
3.3
3.3
3.3
2
V
= 3.3 V and t
3.0V, +85
INT
3.0V, +85
DD
2
2
2
2
f
V
V
V
V
2
+ (C
2.5
°
°
33.3
16.67 MHz = 16.3 mW
16.67 MHz = 1.8 mW
33.3 MHz =
f
C
C
3.3V, +25
3.3V, +25
INT
3.0
3.6V, –40
V
2
MHz = 29.0 mW
DD
+ 50.7 mW.
CK
°
2
°
C
3.5
C
= 30 ns.
°
C
f)
50.7 mW
4.0
3.6 mW
–17–
VALID FOR ALL TEMPERATURE GRADES.
1
2
3
4
POWER REFLECTS DEVICE OPERATING WITH NO OUTPUT LOADS.
IDLE REFERS TO ADSP-21mod870 STATE OF OPERATION DURING EXECUTION OF
TYPICAL POWER DISSIPATION AT 3.3V V
I
IDLE INSTRUCTION. DEASSERTED PINS ARE DRIVEN TO EITHER V
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
MEASUREMENT TAKEN WITH ALL INSTRUCTIONS EXECUTING FROM INTERNAL
250
200
150
100
45
40
35
25
20
15
30
10
45
40
35
30
25
20
15
10
50
5
0
5
0
0
33.3
Figure 15. Power vs. Frequency
33.3
33.3
144mW
112.2mW
87mW
25mW
10mW
23mW
9mW
21mod870 POWER, INTERNAL
21mW
V
DD
23mW
POWER, IDLE n MODES
= 3.3V
POWER, IDLE
1/f
1/f
V
V
V
V
V
1/t
DD
DD
DD
DD
DD
CK
CK
CK
= 3.6V
= 3.0V
= 3.6V
= 3.3V
= 3.0V
– MHz
– MHz
– MHz
DD
ADSP-21mod870
AND +25 C, EXCEPT WHERE SPECIFIED.
1, 2, 3
168.3mW
132mW
216mW
3
35mW
32mW
13mW
12mW
1, 3, 4
52
52
52
32mW
30mW
IDLE
IDLE (16)
IDLE (128)
DD
OR GND.