8

Detailed Description

These ICL32XXE interface ICs operate from a single +3V to

+5.5V supply, guarantee a 250kbps minimum data rate,

require only four small external 0.1

µF capacitors, feature low

power consumption, and meet all ElA RS-232C and V.28

specifications. The circuit is divided into three sections: The

charge pump, the transmitters, and the receivers.

Charge-Pump

Intersil’s new ICL32XXE family utilizes regulated on-chip

dual charge pumps as voltage doublers, and voltage

inverters to generate

±5.5V transmitter supplies from a V

CC

supply as low as 3.0V. This allows these devices to maintain

RS-232 compliant output levels over the

±10% tolerance

range of 3.3V powered systems. The efficient on-chip power

supplies require only four small, external 0.1

µF capacitors

See the “Capacitor Selection” section, and Table 3 for

capacitor recommendations for other operating conditions.

The charge pumps operate discontinuously (i.e., they turn off

as soon as the V+ and V- supplies are pumped up to the

nominal values), resulting in significant power savings.

Transmitters

The transmitters are proprietary, low dropout, inverting

drivers that translate TTL/CMOS inputs to EIA/TIA-232

output levels. Coupled with the on-chip

±5.5V supplies, these

transmitters deliver true RS-232 levels over a wide range of

single supply system voltages.

Transmitter outputs disable and assume a high impedance

state when the device enters the powerdown mode (see

Table 2). These outputs may be driven to

±12V when

disabled.

All devices guarantee a 250kbps data rate for full load

conditions (3k

transmitter operating at full speed. Under more typical

transmitter easily operates at 1Mbps.

Transmitter inputs float if left unconnected, and may cause

performance.

Receivers

All the ICL32XXE devices contain standard inverting

receivers, but only the ICL3244E receivers can three-state,

via the FORCEOFF control line. Additionally, the ICL3244E

includes a noninverting (monitor) receiver (denoted by the

any control lines. Both receiver types convert RS-232 signals

to CMOS output levels and accept inputs up to

±25V while

presenting the required 3k

Ω to 7kΩ input impedance (see

Schmitt trigger input stage uses hysteresis to increase noise

immunity and decrease errors due to slow input signal

transitions.

Receiver Skew

25

-

50

-

ns

Transition Region Slew Rate

Measured From 3V to -3V or -3V

to 3V

25

6

-

30

V/

µs

25

4

8

30

V/

µs

ESD PERFORMANCE

Human Body Model

25

-

±15

-

kV

IEC61000-4-2 Contact Discharge

25

-

±8-

kV

IEC61000-4-2 Air Gap Discharge

25

-

±15

-

kV

All Other Pins

Human Body Model

25

-

±3-

kV

NOTE:

2. An “edge” is defined as a transition through the transmitter or receiver input thresholds.

Electrical Specifications

PARAMETER

TEST CONDITIONS

TEMP

(°C)

MIN

TYP

MAX

UNITS

GND

5k

Ω

-25V

GND

FIGURE 1. INVERTING RECEIVER CONNECTIONS

ICL3224E, ICL3226E, ICL3244E