DescriptionPLCC-68
ManufacturerAnalog Devices

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Page 27/64
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POWER DISSIPATION EXAMPLE
To determine total power dissipation in a specific application,
the following equation should be applied for each output:
2
C
V
f
DD
C = load capacitance, f = output switching frequency.
Example:
In an ADSP-2103 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
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
= 3.3 V and t
DD
Total Power Dissipation = P
INT
P
= internal power dissipation (from Figure 23).
INT
2
(C
V
f ) is calculated for each output:
DD
# of
2
Output
Pins
C
V
DD
2
10 pF
3.3
V
2
Data, WR
9
10 pF
3.3
V
2
RD
1
10 pF
3.3
V
2
CLKOUT
1
10 pF
3.3
V
Total power dissipation for this example = P
ENVIRONMENTAL CONDITIONS
Ambient Temperature Rating:
T
= T
– (PD
)
AMB
CASE
CA
T
= Case Temperature in C
CASE
PD = Power Dissipation in W
= Thermal Resistance (Case-to-Ambient)
CA
= Thermal Resistance (Junction-to-Ambient)
JA
= Thermal Resistance (Junction-to-Case)
JC
Package
JA
PGA
27 C/W
PQFP
60 C/W
REV. B
= 100 ns.
CK
2
Figure 24. Typical Output Rise Time vs. Load Capacitance, C
+ (C
V
f )
DD
(at Maximum Ambient Operating Temperature)
f
10 MHz = 8.71 mW
5 MHz = 4.90 mW
5 MHz = 0.55 mW
10 MHz = 1.09 mW
15.25 mW
+ 15.25 mW.
INT
Figure 25. Typical Output Valid Delay or Hold vs. Load
Capacitance, C
JC
CA
16 C/W
11 C/W
18 C/W
42 C/W
–27–
30
25
V
= 3.0V
DD
20
15
10
5
25
50
75
100
125
150
C
– pF
L
+8
+6
+4
V
= 3.0V
DD
+2
NOMINAL
–2
25
50
75
100
125
150
C
– pF
L
(at Maximum Ambient Operating Temperature)
L
L