simultaneously at 120kbps into RS-232 loads in parallel

with 1000pF. For Figure 9, a single transmitter was dri-

ven at 250kbps, and all transmitters were loaded with

an RS-232 receiver in parallel with 250pF.

The MAX3225/MAX3227/MAX3245 maintain the RS-232

±5.0V minimum transmitter output voltage at data rates

up to 1Mbps (MegaBaud). Figure 10 shows a loopback

test result with a single transmitter driven at 1Mbps and

all transmitters loaded with an RS-232 receiver in paral-

lel with 250pF.

Mouse Driveability

The MAX3244/MAX3245 are specifically designed to

power serial mice while operating from low-voltage

power supplies. They have been tested with leading

mouse brands from manufacturers such as Microsoft

and Logitech. The MAX3244/MAX3245 successfully

drove all serial mice tested and met their respective

current and voltage requirements. The MAX3244/

MAX3245 dual charge pump ensures the transmitters

will supply at least ±5V during worst-case conditions.

Figure 11a shows the transmitter output voltages under

increasing load current. Figure 11b shows a typical

mouse connection.

1µA Supply Current, 1Mbps, 3.0V to 5.5V,

RS-232 Transceivers with AutoShutdown Plus

______________________________________________________________________________________

13

Figure 8. MAX3224/MAX3226/MAX3244 Loopback Test Result

at 120kbps

2

µs/div

T1IN

T1OUT

R1OUT

5V/div

5V/div

5V/div

Figure 9. MAX3224/MAX3226/MAX3244 Loopback Test Result

at 250kbps

2

µs/div

T1IN

T1OUT

R1OUT

5V/div

5V/div

5V/div

Figure 10. MAX3225/MAX3227/MAX3245 Loopback Test

Result at 1Mbps

200ns/div

T1IN

T1OUT

R1OUT

5V/div

5V/div

5V/div

-6

-5

-4

-3

-2

-1

0

1

2

3

4

5

6

0

1

2

3

4

5

6

7

8

9

10

LOAD CURRENT PER TRANSMITTER (mA)

Figure 11a. MAX324_ Transmitter Output Voltage vs. Load

Current per Transmitter