_______________Detailed Description

The MAX214 RS-232 transceiver provides a complete,

8-line, software-configurable, DTE or DCE port RS-232

interface. Tx, Rx, RTS, CTS, DTR, DSR, DCD, and RI

circuits can be configured as either Data Terminal

Equipment (DTE) or Data Circuit-Terminating

Equipment (DCE) using the DTE/DCE control pin. The

MAX214 eliminates the need to swap cables when

switching between DTE and DCE configurations. This

is useful when, for example, a portable computer is

required to communicate with printers, modems, and

other computers without carrying multiple cables.

The MAX214 runs from a single +5V supply and incor-

porates a dual charge-pump voltage converter to gener-

ate the necessary voltages for the RS-232 transmitters.

A shutdown mode is provided to save power when

transmission is not required, but the receivers always

stay active for simple detection of ring indicator signals.

DTE/DCE Operation

The DTE/DCE pin allows circuit configuration under

software control. Tables 1a and 1b show the pin defini-

tions of the MAX214 in both DTE and DCE modes. The

Function columns show the direction of data flow from

the input pin to the output pin of the MAX214, and onto

the corresponding DB-25 connector’s pin.

+5V to ±10V Dual Charge-Pump

Voltage Converter

The +5V to ±10V conversion is performed by two

charge-pump voltage converters (Figure 2). The first

uses capacitor C1 to double the +5V to +10V, storing

the +10V on the output filter capacitor, C3. The second

charge-pump voltage converter uses C2 to invert the

+10V to -10V, storing the -10V on the V- output filter

capacitor, C4.

resistor, and V- falls to GND.

Programmable DTE/DCE,

+5V RS-232 Transceiver

_______________________________________________________________________________________

5

PIN

14

NAME

V-

9, 18, 20

TRA, TRC, TRB

15

V+

7

RDC

6, 8, 22, 23

RA, RE, RC, RB

5, 24, 25

TA, TC, TB

16

10, 17, 19

RTA, RTC, RTB

11

RDTC

21

12

DTE/DCE

RRE

13

GND

26

SHDN

27, 28

3

C1+, C1-

1, 2

C2+, C2-

HI-Z

4

N.C.

FUNCTION

TTL/CMOS receiver A, E, C, B outputs

TTL/CMOS driver A, C, B inputs

+4.5V to +5.5V supply voltage

RS-232 receiver input

Ground

Shutdown control; shutdown high, normal operation low

Terminals for positive charge-pump capacitor

Terminals for negative charge-pump capacitor

No connect—not internally connected

______________________________________________________________Pin Description

RS-232 receiver impedance control. Take high to disconnect the termination resistor.

TTL/CMOS DTE receiver output D for DTE/DCE = 0V, or TTL/CMOS DCE receiver output C for

DTE/DCE = +5V

RS-232 DTE receiver input for DTE/DCE = 0V, or RS-232 DCE driver output for DTE/DCE = +5V

RS-232 DTE receiver input D for DTE/DCE = 0V, or RS-232 DCE driver output C for

DTE/DCE = +5V

Data terminal equipment (DTE) and data circuit-terminating equipment (DCE) control pin.

DCE active high and DTE active low.

RS-232 DTE driver output for DTE/DCE= 0V, or RS-232 DCE receiver input for DTE/DCE = +5V