Datasheet
This information applies to a product under development. Its characteristics and specifications are subject to change with-
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54REV. PrA
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ADSP-2196September 2001
The P
EXT
equation is calculated for each class of pins that
can drive as shown in Table 24.
A typical power consumption can now be calculated for
these conditions by adding a typical internal power dissipa-
tion with the formula in Figure 30.
Where:
• P
EXT
is from Table 24
• P
INT
is I
DDINT
2.5V, using the calculation I
DDINT
listed in
Power Dissipation on page 52
Note that the conditions causing a worst-case P
EXT
are
different from those causing a worst-case P
INT
. Maximum
P
INT
cannot occur while 100% of the output pins are
switching from all ones to all zeros. Note also that it is not
common for an application to have 100% or even 50% of
the outputs switching simultaneously.
Te s t C o n di t i o ns
The DSP is tested for output enable, disable, and hold time.
Output Disable Time
Output pins are considered to be disabled when they stop
driving, go into a high impedance state, and start to decay
from their output high or low voltage. The time for the
voltage on the bus to decay by – V is dependent on the
capacitive load, C
L
and the load current, I
L
. This decay time
can be approximated by the equation in Figure 31.
The output disable time t
DIS
is the difference between
t
MEASURED
and t
DECAY
as shown in Figure 32. The time
t
MEASURED
is the interval from when the reference signal
switches to when the output voltage decays –V from the
measured output high or output low voltage. The t
DECAY
is
calculated with test loads C
L
and I
L
, and with –V equal to
0.5 V.
Output Enable Time
Output pins are considered to be enabled when they have
made a transition from a high impedance state to when they
start driving. The output enable time t
ENA
is the interval
from when a reference signal reaches a high or low voltage
level to when the output has reached a specified high or low
trip point, as shown in the Output Enable/Disable diagram
(Figure 32). If multiple pins (such as the data bus) are
enabled, the measurement value is that of the first pin to
start driving.
Table 24. P
EXT
Calculation
Pin Type # of Pins % Switching
C
f
V
DD
2
= P
EXT
Address 15 50 TBD pF
25.0 MHz
10.9 V =TBD W
MSx
10 TBDpF
25.0 MHz
10.9 V =TBD W
WR
1— TBDpF
25 MHz
10.9 V =TBD W
Data 16 50 TBD pF
25.0 MHz
10.9 V =TBD W
CLKOUT 1 — TBD pF
100 MHz
10.9 V =TBD W
P
EXT
=TBD W
Figure 30. P
TOTAL
(Typical) Calculation
Figure 31. Decay Time Calculation
P
TOTAL
P=
EXT
P
INT
+
t
DECAY
C
L
V
∆
I
L
---------------
=
Figure 32. Output Enable/Disable
3
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