MAX200–MAX209/
MAX211/MAX213
Applications Information
Capacitor Selection
The type of capacitor used is not critical for proper
operation. Ceramic capacitors are suggested. To ensure
proper RS-232 signal levels over temperature when
using 0.1µF capacitors, make sure the capacitance value
does not degrade excessively as the temperature varies.
If in doubt, use capacitors with a larger nominal value.
Also observe the capacitors’ ESR value over tempera-
ture, since it influences the amount of ripple on V+ and
V-. To reduce the output impedance at V+ and V-, use
larger capacitors (up to 10µF). If polarized capacitors are
used, obey the polarities shown in Figure 1 and the pin
configurations.
+5V, RS-232 Transceivers
with 0.1μF External Capacitors
Driver Outputs When Exiting Shutdown
Figure 5 shows two driver outputs exiting shutdown. As
they become active, the two driver outputs go to opposite
RS-232 levels (one driver input is high, the other is low).
Each driver is loaded with 3kΩ in parallel with 2500pF.
The driver outputs display no ringing or undesirable tran-
sients as they come out of shutdown.
Power-Supply Decoupling
In applications that are sensitive to power-supply noise,
decouple V
CC
to ground with a capacitor of the same
value as the charge-pump capacitors.
V+ and V- as Power Supplies
Driving Multiple Receivers
A small amount of power can be drawn from V+ and V-,
although this reduces noise margins.
Each transmitter is designed to drive a single receiver.
Transmitters can be paralleled to drive multiple receivers.
Power Supplies for MAX201/MAX209
If at power-up the V+ supply rises after the V
CC
supply,
place a diode (e.g., 1N914) in series with the V+ supply.
Table 2. Summary of EIA/TIA-232E, V.28 Specifications
PARAMETER
Driver Output Voltage: 0 Level
Driver Output Voltage: 1 Level
Output Level, Maximum
Data Rate
Receiver Input Voltage: 0 Level
Receiver Input Voltage: 1 Level
Input Level, Maximum
Instantaneous Slew Rate, Maximum
Driver Output Short-Circuit Current, Maximum
Transition Rate on Driver Output
Driver Output Resistance
CONDITION
3kΩ to 7kΩ load
3kΩ to 7kΩ load
No load
3kΩ ≤ R
L
≤ 7kΩ, C
L
≤ 2500pF
—
—
—
3kΩ ≤ R
L
≤ 7kΩ, C
L
≤ 2500pF
—
V.28
EIA/TIA-232E
-2V < V
OUT
< +2V
EIA/TIA-232E, V.28 SPECIFICATION
+5.0V to +15V
-5.0V to -15V
±25V
Up to 20kbps
+3.0V to +15V
-3.0V to -15V
±25V
30V/µs
100mA
1ms or 3% of the period
4% of the period
300Ω
Table 3. DB9 Cable Connections Commonly Used for EIA/TIA-232E and V.24
Asynchronous Interfaces
PIN
1
2
3
4
5
6
7
8
9
Receive Data (RD)
Transmit Data (TD)
Data Terminal Ready
Signal Ground
Data Set Ready (DSR)
Request to Send (RTS)
Clear to Send (CTS)
Ring Indicator
NAME
Received Line Signal Detector, sometimes called Carrier Detect (DCD)
CONNECTION
Handshake from DCE
Data from DCE
Data from DTE
Handshake from DTE
Reference point for signals
Handshake from DCE
Handshake from DTE
Handshake from DCE
Handshake from DCE
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