3.0V to 5.5V, Low -Pow e r, up to 1Mbps , True RS-232
Tra ns c e ive rs Us ing Four 0.1µF Exte rna l Ca pa c itors
7/MAX3241
V
CC
5V/div
T1IN
0.1µF
5V/div
5V/div
T1OUT
R1OUT
V
CC
C1+
V+
V-
C3
C4
C1
C1-
C2+
MAX3222
MAX3232
MAX3237
MAX3241
C2
5µs/div
C2-
V
= 3.3V
CC
T_ OUT
T_ IN
Figure 6. MAX3241 Loopback Test Result at 120kbps
R_ IN
5k
R_ OUT
EN*
0V
1000pF
5V/div
T1IN
V
CC
SHDN*
GND
5V/div
5V/div
T1OUT
R1OUT
* MAX3222/MAX3241 ONLY
Figure 5. Loopback Test Circuit
2µs/div
V
CC
= 3.3V
Figure 7. MAX3241 Loopback Test Result at 235kbps
Hig h Da t a Ra t e s
The MAX3222/MAX3232/MAX3241 maintain the RS-232
±5.0V minimum transmitter output voltage even at high
data rates. Figure 5 shows a transmitter loopback test
c irc uit. Fig ure 6 s hows a loop b a c k te s t re s ult a t
120kbps, and Figure 7 shows the same test at 235kbps.
For Figure 6, all transmitters were driven simultaneously
at 120kbps into RS-232 loads in parallel with 1000pF.
For Figure 7, a single transmitter was driven at 235kbps,
and all transmitters were loaded with an RS-232 receiver
in parallel with 1000pF.
+5V
T_IN
0V
+5V
0V
-5V
+5V
0V
T_OUT = R_IN
5k + 250pF
The MAX3237 maintains the RS-232 ±5.0V minimum
transmitter output voltage at data rates up to 1Mbps.
Figure 8 shows a loopback test result at 1Mbps with
R_OUT
150pF
MBAUD = V . For Fig ure 8, a ll tra ns mitte rs we re
loaded with an RS-232 receiver in parallel with 250pF.
200ns/div
CC
V
CC
= 3.3V
Figure 8. MAX3237 Loopback Test Result at 1000kbps
(MBAUD = V
)
CC
______________________________________________________________________________________ 11
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
