MAX3243ECWI Maxim, MAX3243ECWI Datasheet - Page 12

• Manufacturer Part Number: MAX3243ECWI
• Description: 15kV ESD-Protected / 1A / 3.0V to 5.5V / 250kbps / RS-232 Transceivers with AutoShutdown
• Manufacturer: Maxim

The MAX3221E/MAX3223E/MAX3243E maintain the RS-
232 ±5.0V minimum transmitter output voltage even at
high data rates. Figure 9 shows a transmitter loopback
test circuit. Figure 10 shows a loopback test result at
120kbps, and Figure 11 shows the same test at 250kbps.
For Figure 10, all three transmitters were driven simulta-
neously at 120kbps into RS-232 loads in parallel with
1000pF. For Figure 11, a single transmitter was driven at
250kbps, and all three transmitters were loaded with an
RS-232 receiver in parallel with 1000pF.
±15kV ESD-Protected, 1µA, 3.0V to 5.5V, 250kbps,
RS-232 Transceivers with AutoShutdown
12
Figure 9. Loopback Test Circuit
Figure 10. Loopback Test Result at 120kbps
T1OUT
R1OUT
______________________________________________________________________________________
C1
C2
V
T1IN
V
0V
CC
CC
V
0.1 F
CC
= 3.3V
FORCEOFF
T_ IN
R_ OUT
EN (MAX3221/3E)
C1+
C1-
C2+
C2-
MAX3221E
MAX3223E
MAX3243E
2 s/div
GND
V
CC
T_ OUT
5k
R_ IN
High Data Rates
V+
V-
5V/div
5V/div
5V/div
C3
C4
1000pF
The MAX3243E has been specifically designed to power
serial mice while operating from low-voltage power sup-
plies. It has been tested with leading mouse brands such
as Logitech and Microsoft. When tested, the MAX3243E
successfully drove all serial mice and met their respective
current and voltage requirements. The MAX3243E’s regu-
lated dual charge pump ensures the transmitters will sup-
ply at least ±5V during worst-case conditions. Figure 12a
shows the transmitter outputs under increasing load cur-
rent. The AutoShutdown feature does not work with a
mouse, so FORCEOFF and FORCEON should be con-
nected to V
a mouse driver test circuit. To achieve mouse driveability
with 1µA supply current when the port is inactive, use
parts with the AutoShutdown Plus feature (such as the
MAX3244E and MAX3245E).
Figure 11. Loopback Test Result at 250kbps
Figure 12a. Transmitter Output Voltage vs. Load Current per
Transmitter
R1OUT
T1OUT
T1IN
CC
V
CC
. Figure 12b (on the following page) shows
-1
-2
-3
-4
-5
-6
Mouse Driveability (MAX3243E)
6
5
4
3
2
1
0
= 3.3V
0
V
V
CC
CC
1
LOAD CURRENT PER TRANSMITTER (mA)
= 3.0V
2
2 s/div
3
4
5
6
V
V
OUT+
OUT-
7
8
V
V
OUT+
OUT-
9
10
5V/div
5V/div
5V/div