ADSP-2186 Analog Devices, ADSP-2186 Datasheet - Page 28

• Manufacturer Part Number: ADSP-2186
• Description: DSP Microcomputer
• Manufacturer: Analog Devices

ADSP-2186
CAPACITIVE LOADING
Figures 24 and 25 show the capacitive loading characteristics of
the ADSP-2186.
Figure 24. Typical Output Rise Time vs. Load Capacitance,
C
Figure 25. Typical Output Valid Delay or Hold vs. Load
Capacitance, C
Temperature)
TEST CONDITIONS
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 out-
put disable time (t
as shown in the Output Enable/Disable diagram. The time is the
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. The decay time,
t
load, i
lowing equation:
from which
DECAY
L
(at Maximum Ambient Operating Temperature)
NOMINAL
L
, is dependent on the capacitive load, C
, on the output pin. It can be approximated by the fol-
30
25
20
15
10
5
0
0
18
16
14
12
10
–2
–4
–6
8
6
4
2
T = +85 C
V
0
DD
= 4.5V
L
50
(at Maximum Ambient Operating
DIS
t
DIS
) is the difference of t
50
t
DECAY
= t
100
MEASURED
100
C
150
C
L
– pF
L
C
L
– pF
i
– t
L
0.5V
150
200
DECAY
MEASURED
L
250
, and the current
200
and t
300
250
DECAY
,
–28–
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.
Figure 26. Voltage Reference Levels for AC Measure-
ments (Except Output Enable/Disable)
Output Enable Time
Output pins are considered to be enabled when that have made
a transition from a high-impedance state to when they start
driving. The output enable time (t
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. If multiple pins (such as
the data bus) are enabled, the measurement value is that of the
first pin to start driving.
Figure 28. Equivalent Device Loading for AC Measure-
ments (Including All Fixtures)
REFERENCE
(MEASURED)
(MEASURED)
OUTPUT
OUTPUT
SIGNAL
INPUT
OR
V
OUTPUT
V
OL
OH
OUTPUT STOPS
Figure 27. Output Enable/Disable
PIN
t
TO
MEASURED
t
DIS
DRIVING
1.5V
50pF
HIGH-IMPEDANCE STATE. TEST CONDITIONS CAUSE
THIS VOLTAGE LEVEL TO BE APPROXIMATELY 1.5V.
V
V
OH
OL
t
DECAY
(MEASURED) + 0.5V
(MEASURED) – 0.5V
ENA
I
I
OH
OL
) is the interval from when
OUTPUT STARTS
1.0V
2.0V
t
DRIVING
ENA
+1.5V
1.5V
V
(MEASURED)
V
(MEASURED)
OH
OL
REV. A