1ꢀ5k EꢁD-ꢂrotected, +ꢀk Rꢁ-232 Transceivers
+5V
+5V
0.1µF
0.1µF
*
*
0.1µF
0.1µF
0.1µF
0.1µF
*
*
V
V
CC
CC
C1+
C1-
C2+
C2-
V+
V-
C1+
C1-
C2+
C2-
V+
V-
0.1µF
0.1µF
*
*
*
*
*
*
MAX2_ _E
MAX2_ _E
V
CC
V
CC
0.1µF
0.1µF
400k
T_
400k
T_
T_OUT
T_OUT
T_IN
T_IN
R_
2500pF
50pF
R_
3k
7k
R_IN
5k
R_IN
5k
R_OUT
EN (EN)
R_OUT
EN (EN)
0V (+5V)
0V (+5V)
0V (+5V)
0V (+5V)
SHDN (SHDN)
SHDN (SHDN)
MINIMUM SLEW-RATE TEST CIRCUIT
MAXIMUM SLEW-RATE TEST CIRCUIT
( ) ARE FOR MAX213E
* 1µF FOR MAX232E/MAX241E
TRANSMITTER INPUT PULL-UP RESISTORS, ENABLE, AND SHUTDOWN ARE NOT PROVIDED ON THE MAX202E, MAX203E, AND MAX232E.
ENABLE AND SHUTDOWN ARE NOT PROVIDED ON THE MAX207E AND MAX208E.
Figure 3. Transition Slew-Rate Circuit
into -10V, storing the -10V on the V- output filter
capacitor, C4.
_______________Detailed Description
The MAX202E–MAX213E, MAX232E/MAX241E consist of
three sections: charge-pump voltage converters,
drivers (transmitters), and receivers. These E versions
provide extra protection against ESD. They survive
1ꢀ5V discharges to the RS-232 inputs and outputs,
tested using the Human Body Model. When tested
according to IEC1000-4-2, they survive 85V contact-
discharges and 1ꢀ5V air-gap discharges. The rugged
E versions are intended for use in harsh environments
or applications where the RS-232 connection is
frequently changed (such as noteboo5 computers). The
standard (non-“E”) MAX202, MAX203, MAX20ꢀ–
MAX208, MAX211, MAX213, MAX232, and MAX241 are
recommended for applications where cost is critical.
In shutdown mode, V+ is internally connected to V
by
CC
a 15Ω pull-down resistor, and V- is internally connected
to ground by a 15Ω pull up resistor.
Rꢁ-232 Drivers
= ꢀV, the typical driver output voltage swing
With V
CC
is 8V when loaded with a nominal ꢀ5Ω RS-232
receiver. The output swing is guaranteed to meet
EIA/TIA-232E and V.28 specifications that call for ꢀV
minimum output levels under worst-case conditions.
These include a 35Ω load, minimum V , and
CC
maximum operating temperature. The open-circuit
output voltage swings from (V+ - 0.6V) to V-.
Input thresholds are CMOS/TTL compatible. The
unused drivers’ inputs on the MAX20ꢀE–MAX208E,
MAX211E, MAX213E, and MAX241E can be left
+ꢀk to 10k Dual Charge-ꢂuꢃp
koltage Converter
The +ꢀV to 10V conversion is performed by dual
charge-pump voltage converters (Figure 4). The first
charge-pump converter uses capacitor C1 to double
the +ꢀV into +10V, storing the +10V on the output filter
capacitor, C3. The second uses C2 to invert the +10V
unconnected because 4005Ω pull up resistors to V
CC
are included on-chip. Since all drivers invert, the pull up
resistors force the unused drivers’ outputs low. The
MAX202E, MAX203E, and MAX232E do not have pull
up resistors on the transmitter inputs.
_______________________________________________________________________________________
9
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
