adsp-21991 Analog Devices, Inc., adsp-21991 Datasheet - Page 36

• Manufacturer Part Number: adsp-21991
• Description: Mixed Signal Dsp Controller
• Manufacturer: Analog Devices, Inc.

ADSP-21991
Figure 19. Equivalent Device Loading for AC
Measurements (Includes All Fixtures)
Figure 20. Voltage Reference Levels for AC
Measurements (Except Output Enable/Disable)
OUTPUT
OUTPUT
INPUT
OR
PIN
TO
50pF
1.5V
I
I
OL
OH
1.5V
1.5V
–36–
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
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
pins (such as the data bus) are enabled, the measurement value
is that of the first pin to start driving.
Example System Hold Time Calculation
To determine the data output hold time in a particular system,
first calculate t
on Page
voltage of the ADSP-21991 and the input threshold for the device
requiring the hold time. A typical ∆V will be 0.4 V. C
bus capacitance (per data line), and I
state current (per data line). The hold time will be t
minimum disable time (i.e., t
Pin Configurations
Table 16
Table 17
name.
Table 18
Table 19
Table 4
describes each signal.
35. Choose ∆V to be the difference between the output
identifies the signal for each Mini-BGA ball number.
identifies the Mini-BGA ball number for each signal
identifies the signal for each LQFP lead.
identifies the LQFP lead for each signal name.
DECAY
using the equation at
DATRWH
ENA
L
for the write cycle).
is the interval from when a
is the total leakage or three-
(Figure
Output Disable Time
18). If multiple
DECAY
L
is the total
plus the
REV. 0