Datasheet

Applications Information
Capacitor Selection
The capacitor type used for C1–C4 is not critical for prop-
er operation; polarized or nonpolarized capacitors can
be used. The charge pump requires 0.1μF capacitors for
3.3V operation. For other supply voltages, see Table 2 for
required capacitor values. Do not use values 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, and CBYPASS to maintain
the proper ratios (C1 to 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 capacitors
with a larger 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 V
CC
bypass capacitor
is adequate. In applications sensitive to power-supply
noise, use a capacitor of the same value as charge-pump
capacitor C1. Connect bypass capacitors as close to the
IC as possible.
Operation Down to 2.7V
Transmitter outputs meet EIA/TIA-562 levels of ±3.7V
with supply voltages as low as 2.7V.
Figure 6b. Mouse Driver Test Circuit
MAX3241E
EN
23
R5OUT
15
R4OUT
16
R3OUT
17
R2OUT
18
R1OUT
19
R2OUTB
20
R1OUTB
21
5kΩ
5kΩ
5kΩ
5kΩ
5kΩ
R5IN 8
V
CC
R4IN
7
6
R2IN 5
R1IN 4
SHDN
22
GND
25
T3IN
12
T2IN
13
T1IN
14
C2-
2
C2+
1
C1-
24
C1+
28
T3OUT
11
+V
COMPUTER SERIAL PORT
+V
-V
GND
Tx
T2OUT
10
T1OUT
9
V-
3
V+
27
V
CC
V
CC
C4
C3 C1
C2
C
BYPASS
V
CC
= +3.0V TO +5.5V
26
R3IN
MOUSE
www.maximintegrated.com
Maxim Integrated │ 13
MAX3222E/MAX3232E/
MAX3237E/MAX3241E/
MAX3246E
±15kV ESD-Protected, Down to 10nA,
3.0V to 5.5V, Up to 1Mbps,
True RS-232 Transceivers