adm213 Analog Devices, Inc., adm213 Datasheet - Page 12

• Manufacturer Part Number: adm213
• Description: 0.1 Uf, +5 V Powered Cmos Rs-232 Drivers/receivers
• Manufacturer: Analog Devices, Inc.

ADM206–ADM211/ADM213
Receivers R4 and R5 on the ADM213 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
ADM213, where it is active low. See Table 5 and Table 6.
Enable Input
The ADM209, ADM211, and ADM213 feature an enable input
used to enable or disable the receiver outputs. The enable input
is active low on the ADM209 and ADM211 and active high on
the ADM213. See 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.
R
OUT
3V
EN*
0V
* POLARITY OF EN IS REVERSED FOR ADM213.
T
EN
3.5V
0.8V
Figure 24. Enable Timing
T
DIS
V
V
OH
OL
+ 0.1V
– 0.1V
Rev. C | Page 12 of 16
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–ADM211/ADM213
are designed to minimize the slew rate reduction that occurs as
load capacitance increases.
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–ADM211/
ADM213 have 0.65 V of hysteresis to guard against this. This
ensures that even in noisy environments error-free reception
can be achieved.
High Baud Rate Operation
The ADM206–ADM211/ADM213 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 120 kB/s under worst-case loading conditions.