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ADM211E Datasheet(PDF) 11 Page - Analog Devices

Part No. ADM211E
Description  EMI/EMC-Compliant, ±15 kV ESDProtected, RS-232 Line Drivers/Receivers
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Maker  AD [Analog Devices]
Homepage  http://www.analog.com
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 11 page
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ADM206E/ADM207E/ADM208E/ADM211E/ADM213E
Rev. E | Page 11 of 20
On the ADM213E, Receiver R4 and Receiver R5 remain
enabled in shutdown. Note that the transmitters are disabled
but are not tristated in shutdown; it is not permitted to connect
multiple (RS-232) driver outputs together.
The shutdown feature is very useful in battery-operated systems
since it reduces the power consumption to 1 μW. During
shutdown, the charge pump is also disabled. The shutdown
control input is active high on the ADM211E, and it is active
low on the ADM213E. When exiting shutdown, the charge
pump is restarted, and it takes approximately 100 μs for it to
reach its steady state operating condition.
HIGH BAUD RATE
The ADM2xxE feature high slew rates, permitting data
transmission rates well in excess of the EIA-232-E
specifications. RS-232 levels are maintained at data rates up to
230 kbps, even under worst-case loading conditions. This
allows for high speed data links between two terminals, making
it suitable for the new generation modem standards that require
data rates of 200 kbps. The slew rate is controlled internally to
less than 30 V/μs to minimize EMI interference.
tDR
3V
0V
EN INPUT
RECEIVER
OUTPUT
NOTES
1. EN IS THE COMPLEMENT OF EN FOR THE ADM213E.
VOH
VOL
VOH –0.1V
VOL +0.1V
Figure 22. Receiver Disable Timing
tER
3V
0V
EN INPUT
RECEIVER
OUTPUT
+3.5V
+0.8V
NOTES
1. EN IS THE COMPLEMENT OF EN FOR THE ADM213E.
Figure 23. Receiver Enable Timing
ESD/EFT TRANSIENT PROTECTION SCHEME
The ADM2xxE use protective clamping structures on all inputs
and outputs that clamp the voltage to a safe level and dissipate
the energy present in ESD (electrostatic) and EFT (electrical
fast transient) discharges. A simplified schematic of the
protection structure is shown in Figure 24 and Figure 25. Each
input and output contains two back-to-back high speed
clamping diodes. During normal operation, with maximum
RS­232 signal levels, the diodes have no effect because one or
the other is reverse biased, depending on the polarity of the
signal. If, however, the voltage exceeds about ±50 V, reverse
breakdown occurs, and the voltage is clamped at this level. The
diodes are large p-n junctions designed to handle the
instantaneous current surges that can exceed several amperes.
The transmitter outputs and receiver inputs have a similar
protection structure. The receiver inputs can also dissipate some
of the energy through the internal 5 kΩ resistor to GND as well
as through the protection diodes.
The protection structure achieves ESD protection up to
±15 kV and EFT protection up to ±2 kV on all RS-232 I/O
lines. The methods used to test the protection scheme are
discussed in the ESD Testing (IEC 1000­4­2) and EFT/Burst
Testing (IEC 1000­4­4) sections.
RIN
RX
D1
D2
R1
RECEIVER
INPUT
Figure 24. Receiver Input Protection Scheme
TOUT
RX
D1
D2
TRANSMITTER
OUTPUT
Figure 25. Transmitter Output Protection Scheme
ESD TESTING (IEC 1000-4-2)
IEC 1000-4-2 (previously IEC 801-2) specifies compliance
testing using two coupling methods, contact discharge and air-
gap discharge. Contact discharge calls for a direct connection to
the unit being tested. Air-gap discharge uses a higher test voltage
but does not make direct contact with the unit under test. With
air-gap discharge, the discharge gun is moved toward the unit
under test, developing an arc across the air gap. This method is
influenced by humidity, temperature, barometric pressure,
distance, and rate of closure of the discharge gun. The contact
discharge method, while less realistic, is more repeatable and is
gaining acceptance in preference to the air-gap method.
Although very little energy is contained within an ESD pulse,
the extremely fast rise time, coupled with high voltages, can
cause failures in unprotected semiconductors. Catastrophic




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