ues smaller than those listed in Table 2. 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 C2, C3, C4,

the other capacitors).

When using the minimum required capacitor values,

make sure the capacitor value does not degrade

excessively with temperature. If in doubt, use capaci-

tors with a larger nominal value. The capacitor’s equiva-

lent series resistance (ESR), which usually rises at low

temperatures, influences the amount of ripple on V+

and V-.

Power-Supply Decoupling

is adequate. In applications that are sensitive to power-

supply noise, use a capacitor of the same value as

charge-pump capacitor C1. Connect bypass capaci-

tors as close to the IC as possible.

Operation Down to 2.7V

Transmitter outputs will meet EIA/TIA-562 levels of

±3.7V with supply voltages as low as 2.7V.

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 lev-

±15kV ESD-Protected, 3.0V to 5.5V, Low-Power,

up to 250kbps, True RS-232 Transceiver

_______________________________________________________________________________________

7

CHARGE-CURRENT

LIMIT RESISTOR

DISCHARGE

RESISTANCE

STORAGE

CAPACITOR

Cs

100pF

1M

1500

Ω

HIGH-

VOLTAGE

DC

SOURCE

DEVICE

UNDER

TEST

Figure 3a. Human Body ESD Test Model

90%

36.8%

TIME

CURRENT WAVEFORM

PEAK-TO-PEAK RINGING

(NOT DRAWN TO SCALE)

Ir

10%

0

0

AMPERES

Figure 3b. Human Body Model Current Waveform

CHARGE-CURRENT

LIMIT RESISTOR

DISCHARGE

RESISTANCE

STORAGE

CAPACITOR

Cs

150pF

50M to 100M

330

Ω

HIGH-

VOLTAGE

DC

SOURCE

DEVICE

UNDER

TEST

Figure 4a. IEC 1000-4-2 ESD Test Model

tr = 0.7ns to 1ns

30ns

60ns

t

100%

90%

10%

I

Figure 4b. IEC 10000-4-2 ESD Generator Current Waveform