ICL3221, ICL3222, ICL3223, ICL3232, ICL3241, ICL3243

4. Application Information

FN4805 Rev.23.00

Page 20 of 36

Apr.26.19

4.10 Transmitter Outputs when Exiting Powerdown

Figure 14 shows the response of two transmitter outputs when exiting powerdown mode. As they activate, the two

transmitter outputs properly go to opposite RS-232 levels, with no glitching, ringing, nor undesirable transients.

Each transmitter is loaded with 3kΩ in parallel with 2500pF. Note that the transmitters enable only when the

magnitude of the supplies exceed approximately 3V.

4.11 Mouse Driveability

The ICL324X have been specifically designed to power a serial mouse while operating from low voltage supplies.

Figure 15 shows the transmitter output voltages under increasing load current. The on-chip switching regulator

ensures the transmitters will supply at least ±5V during worst case conditions (15mA for paralleled V+

transmitters, 7.3mA for single V- transmitter). The Automatic Powerdown feature does not work with a mouse, so

FORCEOFF and FORCEON should be connected to VCC.

4.12 High Data Rates

The ICL32xx maintain the RS-232 ±5V minimum transmitter output voltages even at high data rates. Figure 16

details a transmitter loopback test circuit, and Figure 17 illustrates the loopback test result at 120kbps. For this

test, all transmitters were simultaneously driving RS-232 loads in parallel with 1000pF at 120kbps. Figure 18

shows the loopback results for a single transmitter driving 1000pF and an RS-232 load at 250kbps. The static

transmitters were also loaded with an RS-232 receiver.

Figure 14. Transmitter Outputs when Exiting Powerdown

Figure 15. Transmitter Output Voltage vs Load Current (per Transmitter, Such as, Double Current Axis for Total VOUT+

Current)

Time (20µs/Div)

T1

T2

2V/Div

5V/Div

VCC = +3.3V

FORCEOFF

C1 - C4 = 0.1µF

Load Current per Transmitter (mA)

02

468

10

-6

-4

-2

0

2

4

6

-5

-3

-1

1

3

5

1

3579

VOUT+

VOUT -

VCC

VOUT+

VOUT -

T1

T2

T3

VCC = 3.0V

ICL3241/43