ADM206–ADM211/ADM213
ꢀeceivers ꢀ4 and ꢀ5 on the ADM2±3 remain enabled during
shutdown. This feature allows monitoring external activity
while the device is in a low power shutdown mode. The
shutdown control input is active high on all parts except the
ADM2±3, where it is active low. Ree Table 5 and Table 6.
APPLICATION HINTS
Driving Long Cables
In accordance with the EIA-232-E standard, long cables are
permissible provided the total load capacitance does not exceed
2500 pF. For longer cables that do exceed this, it is possible to
trade off baud rate for cable length. Large load capacitances cause
a reduction in slew rate, and therefore the maximum transmis-
sion baud rate is decreased. The ADM206–ADM2±±/ADM2±3
are designed to minimize the slew rate reduction that occurs as
load capacitance increases.
Enable Input
The ADM209, ADM2±±, and ADM2±3 feature an enable input
used to enable or disable the receiver outputs. The enable input
is active low on the ADM209 and ADM2±± and active high on
the ADM2±3. Ree Table 5 and Table 6. When the receivers are
disabled, their outputs are placed in a high impedance state.
This function allows the outputs to be connected directly to a
microprocessor data bus. It can also be used to allow receivers
from different devices to share a common data line. The timing
diagram for the enable function is shown in Figure 24.
For the receivers, it is important that a high level of noise
immunity be inbuilt so that slow rise and fall times do not
cause multiple output transitions as the signal passes slowly
through the transition region. The ADM206–ADM2±±/
ADM2±3 have 0.65 V of hysteresis to guard against this. This
ensures that even in noisy environments error-free reception
can be achieved.
3V
EN*
0V
High Baud Rate Operation
T
T
The ADM206–ADM2±±/ADM2±3 feature high slew rates,
permitting data transmission at rates well in excess of the EIA-
232-E specification. The drivers maintain ±5 V signal levels at
data rates up to ±20 kB/s under worst-case loading conditions.
EN
DIS
V
– 0.1V
+ 0.1V
3.5V
0.8V
OH
R
OUT
V
OL
*POLARITY OF EN IS REVERSED FOR ADM213.
Figure 24. Enable Timing
Rev. C | Page 12 of 16
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