adsp-2109lkp-55 Analog Devices, Inc., adsp-2109lkp-55 Datasheet - Page 15

• Manufacturer Part Number: adsp-2109lkp-55
• Description: Low Cost Dsp Microcomputers
• Manufacturer: Analog Devices, Inc.

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SPECIFICATIONS (ADSP-2104/ADSP-2109)
TEST CONDITIONS
Figure 10 shows voltage reference levels for ac measurements.
Figure 10. Voltage Reference Levels for AC Measurements
(Except Output Enable/Disable)
Output Disable Time
Output pins are considered to be disabled when they have
stopped driving and started a transition from the measured
output high or low voltage to a high impedance state. The
output disable time (t
t
interval from when a reference signal reaches a high or low
voltage level to when the output voltages have changed by 0.5 V
from the measured output high or low voltage.
DECAY
, as shown in Figure 11. The time t
OUTPUT
INPUT
V
V
DIS
OH
OL
(MEASURED)
(MEASURED)
) is the difference of t
REFERENCE
SIGNAL
OUTPUT
Figure 12. Equivalent Device Loading for AC Measurements
(Except Output Enable/Disable)
t
DECAY
OUTPUT STOPS
t
MEASURED
MEASURED
t
DIS
DRIVING
2.0V
1.5V
0.8V
3.0V
1.5V
0.0V
OUTPUT
MEASURED
Figure 11. Output Enable/Disable
PIN
TO
is the
V
V
OH
OL
50pF
(MEASURED) – 0.5V
(MEASURED) +0.5V
and
–15–
The decay time, t
C
approximated by the following equation:
from which
is calculated. If multiple pins (such as the data bus) are dis-
abled, the measurement value is that of the last pin to stop
driving.
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
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 Figure 11. If multiple pins (such as the data bus)
are enabled, the measurement value is that of the first pin to
start driving.
I
I
OL
HIGH-IMPEDANCE STATE.
TEST CONDITIONS CAUSE
THIS VOLTAGE LEVEL TO BE
APPROXIMATELY 1.5V.
OH
L
, and the current load, i
OUTPUT STARTS
1.0V
2.0V
DRIVING
+1.5V
t
DECAY
ENA
t
DIS
t
DECAY
ADSP-2104/ADSP-2109
, is dependent on the capacitative load,
= t
L
MEASURED
, on the output pin. It can be
V
V
C
OH
OL
L
(MEASURED)
(MEASURED)
E NA
i
– t
0.5 V
L
) is the interval from
DECAY