Datasheet

Power-Supply Decoupling
In most circumstances, a 0.1μF bypass capacitor is
adequate. In applications that are sensitive to power-
supply noise, decouple V
CC
to ground with 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 will meet EIA/TIA-562 levels of ±3.7V
with supply voltages as low as 2.7V.
Transmitter Outputs when
Exiting Shutdown
Figure 3 shows two transmitter outputs when exiting shut-
down mode. As they become active, the two transmitter
outputs are shown going to opposite RS-232 levels (one
transmitter input is high, the other is low). Each transmit-
ter is loaded with 3kΩ in parallel with 2500pF. The trans-
mitter 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.
Mouse Driveability
The MAX3241 has been specifically designed to power
serial mice while operating from low-voltage power sup-
plies. It has been tested with leading mouse brands
from manufacturers such as Microsoft and Logitech. The
MAX3241 successfully drove all serial mice tested and
met their respective current and voltage requirements.
Figure 4a shows the transmitter output voltages under
increasing load current at 3.0V. Figure 4b shows a typical
mouse connection using the MAX3241.
Table 1. MAX3222/MAX3237/MAX3241
Shutdown and Enable Control Truth Table
Table 2. Required Minimum Capacitor
Values
Figure 3. Transmitter Outputs when Exiting Shutdown or
Powering Up
SHDN EN T_OUT R_OUT
R_OUTB
(MAX3237/
MAX3241)
0 0 High-Z Active Active
0 1 High-Z High-Z Active
1 0 Active Active Active
1 1 Active High-Z Active
V
CC
(V)
C1
(µF)
C2, C3, C4
(µF)
MAX3222/MAX3232/MAX3241
3.0 to 3.6 0.1 0.1
4.5 to 5.5 0.047 0.33
3.0 to 5.5 0.1 0.47
MAX3237
3.0 to 3.6 0.22 0.22
3.15 to 3.6 0.1 0.1
4.5 to 5.5 0.047 0.33
3.0 to 5.5 0.22 1.0
5V/div
V
CC
= 3.3V
C1–C4 = 0.1
µF
2V/div
T2
50
µs/div
T1
MAX3222/MAX3232/
MAX3237/MAX3241
3.0V to 5.5V, Low-Power, Up to 1Mbps,
True RS-232 Transceivers
www.maximintegrated.com
Maxim Integrated │ 9