+3.0V to +5.5V, 10nA, 250kbps RS-232 Transceivers

with ±15kV ESD-Protected I/O and Logic Pins

______________________________________________________________________________________

13

MAX3238E

MAX3248E

RS-232

OUTPUTS

LOGIC

INPUTS

RS-232

INPUTS

LOGIC

OUTPUTS

FORCEOFF

INVALID

AutoShutdown Plus

FORCEON

T1IN

T1OUT

T2IN

T2OUT

T3IN

T3OUT

T4IN

T4OUT

T5IN

5

6

7

10

12

T5OUT

15

24

23

22

19

C1+

V+

C1-

C2+

V-

C2-

27

26

4

28

0.1

µF

0.1

µF

0.1

µF

1

µF

+3.3V

25

1

3

17

R1OUTB

16

R1OUT

8

R1IN

21

R2OUT

9

R2IN

20

R3OUT

11

5k

Ω

5k

Ω

5k

Ω

GND

2

R3IN

18

14

13

T1

T2

T3

T4

T5

R1

R2

R3

0.1

µF*

Typical Operating Circuit

___________________Chip Information

TRANSISTOR COUNT: 2110

and Figure 10 shows the same test at 250kbps. For

Figure 9, all transmitters were driven simultaneously at

120kbps into RS-232 loads in parallel with 1000pF. For

Figure 10, a single transmitter was driven at 250kbps,

and all transmitters were loaded with an RS-232 receiv-

er in parallel with 1000pF.

Data Cable Applications

The MAX3238E/MAX3248Es’ ±15kV ESD protection on

both the RS-232 I/Os as well as the logic I/Os makes

them ideal candidates for data cable applications. A

data cable is both an electrical connection and a level

translator, allowing ultra-miniaturization of cell phones

and other small portable devices.

Previous data cable approaches suffered from com-

plexity due to the required protection circuits on both

the logic side of the cable as well as on the RS-232

connections. The example shown in Figure 10 shows

the ease of using the MAX3238E/MAX3248E in data

cable applications.

The MAX3238E/MAX3248Es’ five-transmitter and three-

receiver configuration is optimized for a data communi-

cation equipment (DCE) application, allowing full hard-

ware handshaking. The 9-pin RS-232 connector is

configured for direct attachment to a PC’s serial port.

R1OUTB is also connected to the subminiature con-

nector. This allows the remote system to shut down

until the PC asserts the ready to send (RTS) signal.

R1OUTB stays active when the MAX3238E/MAX3248E

is shut down (FORCEOFF = GND).