Power-Supply Decoupling

In most circumstances, a 0.1µF bypass capacitor is ade-

quate. In applications sensitive to power-supply noise,

value as charge-pump capacitor C1. Connect bypass

capacitors as close to the IC as possible.

High Data Rates

The MAX3322E/MAX3323E maintain the RS-232 ±5.0V

minimum transmitter output voltage even at high data

rates. Figure 10 shows a transmitter loopback test cir-

cuit. Figure 11 shows a loopback test result at

125kbps, and Figure 12 shows the same test at

250kbps. For Figure 11, all transmitters were driven

simultaneously at 125kbps into RS-232 loads in parallel

with 1000pF. For Figure 12, a single transmitter was dri-

ven at 250kbps, and all transmitters were loaded with

an RS-232 receiver in parallel with 1000pF.

Interconnection with 3V and 5V Logic

The MAX3322E/MAX3323E can directly interface with

various 5V logic families, including ACT and HCT

output voltage level of the receivers and the input

thresholds of the transmitters.

±15kV ESD-Protected, RS-232 Transceivers for

Multidrop Applications

10

______________________________________________________________________________________

MAX3323E

R_OUT

GND

T_IN

C2-

5

C2+

4

C1-

3

C1+

1

R_IN

5k

Ω

T_OUT

V-

6

V+

2

SHDN

C4

0.1

µF

1000pF

C3

0.1

µF

C1

0.1

µF

0.1

µF

C2

0.1

µF

+3.3V

Figure 10. Loopback Test Circuit

MAX3322E fig11

2

µs/div

T1IN

5V/div

T1OUT

5V/div

R1OUT

5V/div

Figure 11. Loopback Test Results at 125kbps

MAX3322E fig12

1

µs/div

T1IN

5V/div

T1OUT

5V/div

R1OUT

5V/div

Figure 12. Loopback Test Results at 250kbps