+5V, RS-232 Transceivers
with 0.1µF External Capacitors
MAX200–MAX209/MAX211/MAX213
Applications Information
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 0.1FF 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 tem-
perature, 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 10FF). If polarized capaci-
tors are used, obey the polarities shown in Figure 1 and
the pin configurations.
Each transmitter is designed to drive a single receiver.
Transmitters can be paralleled to drive multiple receivers.
Capacitor Selection
Figure 5 shows two driver outputs exiting shutdown. As
they become active, the two driver outputs go to oppo-
site RS-232 levels (one driver input is high, the other
is low). Each driver is loaded with 3kI in parallel with
2500pF. The driver outputs display no ringing or undesir-
able transients as they come out of shutdown.
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.
A small amount of power can be drawn from V+ and V-,
although this reduces noise margins.
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.
Driver Outputs When Exiting Shutdown
Power-Supply Decoupling
V+ and V- as Power Supplies
Driving Multiple Receivers
Power Supplies for MAX201/MAX209
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
3kI to 7kI load
3kI to 7kI load
No load
3kI
P
R
L
P
7kI, C
L
P
2500pF
—
—
—
3kI
P
R
L
P
7kI, C
L
P
2500pF
—
V.28
EIA/TIA-232E
-2V < V
OUT
< +2V
EIA/TIA-232E, V.28 SPECIFICATION
+5.0V to +15V
-5.0V to -15V
Q25V
Up to 20kbps
+3.0V to +15V
-3.0V to -15V
Q25V
30V/Fs
100mA
1ms or 3% of the period
4% of the period
300I
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
8
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
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
