ADSP-2187L Analog Devices, ADSP-2187L Datasheet - Page 18

• Manufacturer Part Number: ADSP-2187L
• Description: DSP Microcomputer
• Manufacturer: Analog Devices

ADSP-2187L
CAPACITIVE LOADING
Figures 15 and 16 show the capacitive loading characteristics of
the ADSP-2187L.
Figure 15. Typical Output Rise Time vs. Load Capacitance,
C
TEST CONDITIONS
Output Disable Time
Output pins are considered to be disabled when they have
stopped driving and started a transition from the measured out-
put high or low voltage to a high impedance state, see Figure
17. The output disable time (t
t
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
dependent on the capacitive load, C
on the output pin. It can be approximated by the following
equation:
from which
is calculated. If multiple pins (such as the data bus) are disabled,
the measurement value is that of the last pin to stop driving.
MEASURED
L
Figure 16. Typical Output Valid Delay or Hold vs. Load
Capacitance, C
Temperature)
(at Maximum Ambient Operating Temperature)
NOMINAL
18
16
14
12
10
10
–1
–2
–3
–4
8
6
4
2
0
and t
9
8
7
6
5
4
3
2
1
0
0
T = +85 C
V
DECAY
DD
20
L
= 3.0V
(at Maximum Ambient Operating
t
50
DIS
40
, see Figure 18. The time is the interval
t
DECAY
60
t
MEASURED
100
80
DIS
C
C
C
) is the difference between
100
L
L
L
– pF
– pF
• 0.5V
L
i
L
– t
, and the current load, i
150
120
DECAY
140
200
160
180
250
DECAY
200
L
, is
,
–18–
Figure 17. Voltage Reference Levels for AC Measure-
ments (Except Output Enable/Disable)
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
a reference signal reaches a high or low voltage level to when
the output has reached a specified high or low trip point, see
Figure 18. If multiple pins (such as the data bus) are enabled,
the measurement value is that of the first pin to start driving.
ENVIRONMENTAL CONDITIONS
Ambient Temperature Rating is shown below:
Package
TQFP
REFERENCE
Figure 19. Equivalent Device Loading for AC Measure-
ments (Including All Fixtures)
T
T
PD = Power Dissipation in W
OUTPUT
CA
J A
J C
(MEASURED)
(MEASURED)
AMB
CASE
OUTPUT
SIGNAL
= Thermal Resistance (Junction-to-Ambient)
= Thermal Resistance (Junction-to-Case)
INPUT
= Thermal Resistance (Case-to-Ambient)
= T
OR
= Case Temperature in C
V
V
OUTPUT
OL
OH
CASE
Figure 18. Output Enable/Disable
OUTPUT STOPS
PIN
t
TO
t
MEASURED
DIS
DRIVING
– (PD
50 C/W
1.5V
JA
50pF
HIGH-IMPEDANCE STATE. TEST CONDITIONS CAUSE
V
V
THIS VOLTAGE LEVEL TO BE APPROXIMATELY 1.5V.
OH
OL
t
DECAY
(MEASURED) +0.5V
(MEASURED) – 0.5V
CA
)
ENA
I
I
OH
OL
2 C/W
) is the interval from when
JC
OUTPUT STARTS
1.0V
2.0V
DRIVING
t
ENA
+1.5V
1.5V
V
(MEASURED)
V
(MEASURED)
OH
OL
48 C/W
CA
REV. 0