7

FN8037.7

June 10, 2010

Detailed Description

The ISL4241E and ISL4243E both operate from a single

+2.7V to +5.5V supply, guarantee a 250kbps minimum data

rate, require only four small external 0.1µF capacitors,

feature low power consumption, and meet all ElA RS-232C

divided into three sections: The charge pump, the

transmitters, and the receivers.

Charge-Pump

Intersil’s new ISL4241E, ISL4243E devices utilize regulated

on-chip dual charge pumps as voltage doublers, and voltage

supply as low as 3.0V. This allows them 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 0.1µF capacitors for the

voltage doubler and inverter functions. 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.

All transmitter outputs disable and assume a high

impedance state when the device enters the power-down

mode (see Table 2). These outputs may be driven to ±12V

when disabled.

The devices guarantee a 250kbps data rate for full load

conditions (3k

transmitter operating at full speed. Under more typical

transmitter easily operates at 900kbps.

Transmitter inputs float if left unconnected, and may cause

performance.

Receivers

All the ISL4241E, ISL4243E’s devices contain standard

inverting receivers that are three-state via the EN or

FORCEOFF control lines. Additionally, the ISL4241E,

ISL4243E’s products include noninverting (monitor)

active, regardless of the state of any control lines. All the

receivers convert RS-232 signals to CMOS output levels and

accept inputs up to

±25V while presenting the required 3kΩ

to 7k

Ω input impedance (see Figure 1) even if the power is

uses hysteresis to increase noise immunity and decrease

errors due to slow input signal transitions.

The ISL4241E inverting receivers disable only when EN is

driven high. ISL4243E receivers disable during forced

(manual) power-down, but not during automatic power-down

(see Table 2).

Transition Region Slew Rate

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

2500pF

25

4

9

30

V/µs

Full

4

8

30

V/µs

1000pF

25

6

11

30

V/µs

Full

6

10

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

-

±2

-

kV

NOTE:

3. Transmitter skew is measured at the transmitter zero crossing points.

4. Parameters with MIN and/or MAX limits are 100% tested at +25°C, unless otherwise specified. Temperature limits established by characterization

and are not production tested.

Electrical Specifications

PARAMETER

TEST CONDITIONS

TEMP

(°C)

MIN

(Note 4)

TYP

MAX

(Note 4) UNITS

GND

5k

Ω

-25V

GND

FIGURE 1.

INVERTING RECEIVER CONNECTIONS

ISL4241E, ISL4243E