ADSP-2101BS-100 Datasheet, PDF (20/64 Pages) Analog Devices – TigerSHARC Embedded Processor

ADSP-21xx
SPECIFICATIONS (ADSP-2101/2105/2115/2161/2163)
TEST CONDITIONS
Figure 14 shows voltage reference levels for ac measurements.
The decay time, t_DECAY, is dependent on the capacitative load,
C_L, and the current load, i_L, on the output pin. It can be
approximated by the following equation:
INPUT
OUTPUT
3.0V
1.5V
0.0V
2.0V
1.5V
0.8V
Figure 14. 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_DIS) is the difference of t_MEASURED and
t_DECAY, as shown in Figure 15. The time t_MEASURED 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.
from which
t_DECAY
=
C_L × 0.5 V
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.
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 Figure 15. 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
t_DIS
V_OH (MEASURED)
OUTPUT
V_OL (MEASURED)
t_DECAY
V_OH (MEASURED) – 0.5V
V_OL (MEASURED) +0.5V
t_ENA
2.0V
1.0V
OUTPUT STOPS
DRIVING
OUTPUT STARTS
DRIVING
HIGH-IMPEDANCE STATE.
TEST CONDITIONS CAUSE
THIS VOLTAGE LEVEL TO BE
APPROXIMATELY 1.5V.
V_OH (MEASURED)
V_OL (MEASURED)
Figure 15. Output Enable/Disable
I_OL
TO
OUTPUT
PIN
50pF
+1.5V
I_OH
Figure 16. Equivalent Device Loading for AC Measurements
(Except Output Enable/Disable)
–20–
REV. B