3.0V to 5.5V, Low-Power, up to 1Mbps, True RS-232

Transceivers Using Four 0.1µF External Capacitors

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11

High Data Rates

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

circuit. Figure 6 shows a loopback test result at

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.

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

loaded with an RS-232 receiver in parallel with 250pF.

MAX3222

MAX3232

MAX3237

MAX3241

5k

R_ IN

R_ OUT

EN

*

C2-

C2+

C1-

C1+

V-

V+

C4

C3

C1

C2

0.1

µF

SHDN

*

T_ OUT

T_ IN

GND

0V

1000pF

T1IN

R1OUT

T1OUT

5V/div

5V/div

5V/div

5

µs/div

Figure 5. Loopback Test Circuit

Figure 6. MAX3241 Loopback Test Result at 120kbps

T1IN

R1OUT

T1OUT

5V/div

5V/div

2

µs/div

5V/div

Figure 7. MAX3241 Loopback Test Result at 235kbps

+5V

0V

+5V

0V

-5V

+5V

0V

T_IN

T_OUT = R_IN

5k + 250pF

R_OUT

150pF

200ns/div

Figure 8. MAX3237 Loopback Test Result at 1000kbps