9 Application and Implementation

Note

Information in the following applications sections is not part of the TI component specification,

and TI does not warrant its accuracy or completeness. TI’s customers are responsible for

determining suitability of components for their purposes, as well as validating and testing their design

implementation to confirm system functionality.

9.1 Application Information

The MAX3221 line driver and receiver is a specialized device for 3-V to 5.5-V RS-232 communication

applications. This application is a generic implementation of this device with all required external components.

For proper operation, add capacitors as shown in Figure 9-1.

9.2 Typical Application

ROUT and DIN connect to UART or general purpose logic lines. FORCEON and FORCEOFF may be connected

general purpose logic lines or tied to ground or VCC. INVALID may be connected to a general purpose logic

line or left unconnected. RIN and DOUT lines connect to a RS232 connector or cable. DIN, FORCEON, and

FORCEOFF inputs must not be left unconnected.

CBYPASS = 0.1 µF

Auto-

powerdown

VCC

C1

C2, C3, and C4

3.3 V

± 0.3 V

5 V

± 0.5 V

3 V to 5.5 V

0.1 µF

0.047 µF

0.1 µF

0.1 µF

0.33 µF

0.47 µF

VCC vs CAPACITOR VALUES

FORCEOFF

+

−

+

−

+

−

+

−

+

−

1

8

2

3

5

6

7

4

16

13

12

11

10

9

15

14

VCC

GND

C1+

V+

C2+

C1−

C2−

V−

DOUT

FORCEON

DIN

INVALID

ROUT

EN

RIN

C1

C2

C4

5 k

Ω

C3†

† C3 can be connected to VCC or GND.

NOTES: A. Resistor values shown are nominal.

B. Nonpolarized ceramic capacitors are acceptable. If polarized tantalum or electrolytic capacitors are used, they should be

connected as shown.

Figure 9-1. Typical Operating Circuit and Capacitor Values

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MAX3221

SLLS348P – JUNE 1999 – REVISED JULY 2021

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