±15kV ESD-Protected, 2.5V, 1µA, 460kbps,

RS-232 Compatible Transceivers

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13

Capacitor Selection

The capacitor type used for C1–C4 is not critical for

proper operation; polarized or nonpolarized capacitors

can be used. The charge pump requires 0.1µF capaci-

tors. Increasing the capacitor values (e.g., by a factor of

2) reduces ripple on the transmitter outputs and slightly

reduces power consumption. C2, C3, and C4 can be

increased without changing C1’s value. However, do

not increase C1 without also increasing the values of

(C1 to other capacitors).

When using the minimum-required capacitor values,

make sure the capacitor value does not degrade exces-

sively with temperature. If in doubt, use capacitors with

a higher nominal value. The capacitor’s equivalent

series resistance (ESR), which usually rises at low tem-

peratures, influences the amount of ripple on V+ and V-.

Power-Supply Decoupling

In most circumstances, a 0.1µF bypass capacitor is

adequate. In applications that are sensitive to power-

of the same value as charge pump capacitor C1.

Connect bypass capacitors as close to the IC as possible.

Transmitter Outputs when

Exiting Shutdown

Figure 2 shows two transmitter outputs when exiting

shutdown mode. As they become active, the two trans-

mitter outputs are shown going to opposite RS-232 com-

patible levels (one transmitter input is high, the other is

low). Each transmitter is loaded with 3k

Ω in parallel with

2500pF. The transmitter outputs display no ringing or

undesirable transients as they come out of shutdown.

Note that the transmitters are enabled only when the

magnitude of V- exceeds approximately -3V.

High Data Rates

The MAX3316E–MAX3319E maintain RS-232 compatible

±3.7V minimum transmitter output voltage even at high

data rates. Figure 8 shows a transmitter loopback test

circuit. Figure 9 shows a loopback test result at

230kbps. For Figure 9, all transmitters were driven

simultaneously at 230kbps into EIA/TIA-562 loads in

parallel with 1000pF.

Chip Information

TRANSISTOR COUNT: 1130

MAX3316E

MAX3317E

MAX3318E

MAX3319E

5k

R_ IN

R_ OUT

FORCEON**

C2-

C2+

C1-

C1+

V-

V+

C4

C3*

C1

C2

FORCEOFF**

**MAX3318E/MAX3319E

T_ OUT

T_ IN

GND

1000pF

Figure 8. Loopback Test Circuit

2V/div

5V/div

2V/div

T1 IN

T1 OUT

R1 OUT

Figure 9. Loopback Test Result at 230kbps