Datasheet

ADSP-21261/ADSP-21262/ADSP-21266
Rev. G | Page 37 of 48 | December 2012
OUTPUT DRIVE CURRENTS
Figure 28 shows typical I-V characteristics for the output driv-
ers of the ADSP-2126x. 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 16 on Page 18 through Table 37 on Page 36. These include
output disable time, output enable time, and capacitive loading.
Timing is measured on signals when they cross the 1.5 V level as
described in Figure 30. 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 29). Figure 32 shows graphically
how output delays and holds vary with load capacitance (note
that this graph or derating does not apply to output disable
delays). The graphs of Figure 31, Figure 32, and Figure 33 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 28. Typical Drive
Figure 29. Equivalent Device Loading for AC Measurements
(Includes All Fixtures)
Figure 30. Voltage Reference Levels for AC Measurements
SWEEP (V
DDEXT
) VOLTAGE (V)
–20
03.50.5 1 1.5 2 2.5 3
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
1.5V
30pF
TO
OUTPUT
PIN
50⍀
INPUT
OR
OUTPUT
1.5V 1.5V
Figure 31. Typical Output Rise Time
(20% to 80%, V
DDEXT
= Max)
Figure 32. 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)
1
2
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