ADSP-2183_15 Datasheet, PDF (25/31 Pages) Analog Devices – DSP Microcomputer

ADSP-2183
CAPACITIVE LOADING
Figures 22 and 23 show the capacitive loading characteristics of
the ADSP-2183.
25
T = +85؇C
V_DD = 3.0V
20
15
10
5
0
0 20 40 60 80 100 120 140 160 180 200
C_L – pF
Figure 22. Typical Output Rise Time vs. Load Capacitance,
C_L (at Maximum Ambient Operating Temperature)
18
16
14
12
10
8
6
4
2
NOMINAL
–2
–4
–6
0
40
80
120
160
200
C_L – pF
Figure 23. Typical Output Valid Delay or Hold vs. Load
Capacitance, C_L (at Maximum Ambient Operating
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_DIS) is the difference of t_MEASURED and t_DECAY,
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_DECAY, is dependent on the capacitive load, C_L, and the current
load, i_L, on the output pin. It can be approximated by the fol-
lowing equation:
from which
t_DECAY
=
C_L
• 0.5V
i_L
t_DIS = t_MEASURED – t_DECAY
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.
INPUT
OR
OUTPUT
1.5V
1.5V
Figure 24. 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_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. If multiple pins (such as
the data bus) are enabled, the measurement value is that of the
first pin to start driving.
REFERENCE
SIGNAL
t_MEASURED
V_OH tDIS
(MEASURED)
OUTPUT
V_OL
(MEASURED)
V_OH (MEASURED) – 0.5V
V_OL (MEASURED) +0.5V
t_DECAY
t_ENA
2.0V
1.0V
V_OH
(MEASURED)
V_OL
(MEASURED)
OUTPUT STOPS
DRIVING
OUTPUT STARTS
DRIVING
HIGH-IMPEDANCE STATE. TEST CONDITIONS CAUSE
THIS VOLTAGE LEVEL TO BE APPROXIMATELY 1.5V.
Figure 25. Output Enable/Disable
I_OL
TO
OUTPUT
PIN
50pF
+1.5V
I_OH
Figure 26. Equivalent Device Loading for AC Measure-
ments (Including All Fixtures)
ENVIRONMENTAL CONDITIONS
Ambient Temperature Rating:
T_AMB = T_CASE – (PD × θ_CA)
T_CASE = Case Temperature in °C
PD = Power Dissipation in W
θ_CA = Thermal Resistance (Case-to-Ambient)
θ_JA = Thermal Resistance (Junction-to-Ambient)
θ_JC = Thermal Resistance (Junction-to-Case)
Package
LQFP
Mini-BGA
␪_JA
50°C/W
70.7°C/W
␪_JC
2°C/W
7.4°C/W
␪_CA
48°C/W
63.3°C/W
REV. C
–25–