ADM206–ADM211/ADM213

Rev. C | Page 12 of 16

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.

3V

0V

3.5V

0.8V

* POLARITY OF EN IS REVERSED FOR ADM213.

EN*

Figure 24. Enable Timing

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.