Datasheet
ADSP-21371/ADSP-21375
Rev. D | Page 49 of 56 | April 2013
OUTPUT DRIVE CURRENTS
Figure 36 shows typical I-V characteristics for the output driv-
ers of the processors. The curves represent the current drive
capability of the output drivers as a function of output voltage.
TEST CONDITIONS
The ac signal specifications (timing parameters) appear in
Table 15 on Page 22 through Table 41 on Page 48. These include
output disable time, output enable time, and capacitive loading.
The timing specifications for the SHARC apply for the voltage
reference levels in Figure 37.
Timing is measured on signals when they cross the 1.5 V level as
described in Figure 38. All delays (in nanoseconds) are mea-
sured between the point that the first signal reaches 1.5 V and
the point that the second signal reaches 1.5 V.
CAPACITIVE LOADING
Output delays and holds are based on standard capacitive loads:
30 pF on all pins (see Figure 37). Figure 41 shows graphically
how output delays and holds vary with load capacitance. The
graphs of Figure 39, Figure 40, and Figure 41 may not be linear
outside the ranges shown for Typical Output Delay vs. Load
Capacitance and Typical Output Rise Time (20% to 80%,
V = Min) vs. Load Capacitance.
Figure 36. Typical Drive at Junction Temperature
Figure 37. Equivalent Device Loading for AC Measurements
(Includes All Fixtures)
Figure 38. Voltage Reference Levels for AC Measurements
SWEEP (V
DDEXT
)VOLTAGE(V)
-
20
0 3.50.5 1.0 1.5 2.0 2.5 3.0
0
-
40
-
30
20
40
-
10
S
O
U
R
C
E
(
V
D
D
E
X
T
)
C
U
R
R
E
N
T
(
m
A
)
V
OL
3.11V, 125°C
3.3V, 25°C
3.47V,
-
45°C
V
OH
30
10
3.11V, 125°C
3.3V, 25°C
3.47V,
-
45°C
TO
OUTPUT
PIN
ȍ
V
LOAD
30pF
INPUT
OR
OUTPUT
1.5V 1.5V
Figure 39. Typical Output Rise/Fall Time (20% to 80%,
V
DDEXT
= Max)
Figure 40. Typical Output Rise/Fall Time (20% to 80%,
V
DDEXT
= Min)
LOAD CAPACITANCE (pF)
8
0
0
100 250
12
4
2
10
6
R
I
S
E
A
N
D
F
A
L
L
T
I
M
E
S
(
n
s
)
20015050
FALL
y = 0.0467x + 1.6323
y = 0.045x + 1.524
RISE
LOAD CAPACITANCE (pF)
12
0 50 100 150 200 250
10
8
6
4
R
I
S
E
A
N
D
F
A
L
L
T
I
M
E
S
(
n
s
)
2
0
RISE
FALL
y = 0.049x + 1.5105
y=0.0482x + 1.4604