ICL3221E INTERSIL [Intersil Corporation], ICL3221E Datasheet - Page 11

• Manufacturer Part Number: ICL3221E
• Manufacturer: INTERSIL [Intersil Corporation]

Detailed Description
ICL32xxE interface ICs operate from a single +3V 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 and V.28
specifications. The circuit is divided into three sections:
charge pump, transmitters and 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
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 0.1μF capacitors for the
voltage doubler and inverter functions at V
“Capacitor Selection” on page 14., 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.
Except for the ICL3232E, all 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 (3kΩ and 1000pF), V
transmitter operating at full speed. Under more typical
conditions of V
transmitter easily operates at 900kbps.
Transmitter inputs float if left unconnected, and may cause
I
performance.
Receivers
All the ICL32xxE devices contain standard inverting receivers
that three-state (except for the ICL3232E) via the EN or
FORCEOFF control lines. Additionally, the two ICL324XE
products include noninverting (monitor) receivers (denoted by
the ROUTB label) that are always 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 3kW to 7kW input impedance
(see Figure 1) even if the power is off (VCC = 0V). The
receivers’ Schmitt trigger input stage uses hysteresis to
increase noise immunity and decrease errors due to slow
input signal transitions.
CC
increases. Connect unused inputs to GND for the best
CC
≥ 3.3V, R
ICL3221E, ICL3222E, ICL3223E, ICL3232E, ICL3241E, ICL3243E
L
11
= 3kΩ, and C
CC
≥ 3.0V, with one
CC
L
= 250pF, one
CC
= 3.3V. See
supply as
The ICL3221E, ICL3222E, ICL3223E, ICL3241E inverting
receivers disable only when EN is driven high. ICL3243E
receivers disable during forced (manual) powerdown, but not
during automatic powerdown (see Table 2).
ICL3241E and ICL3243E monitor receivers remain active
even during manual powerdown and forced receiver disable,
making them extremely useful for Ring Indicator monitoring.
Standard receivers driving powered down peripherals must be
disabled to prevent current flow through the peripheral’s
protection diodes (see Figures 2 and 3). This renders them
useless for wake up functions, but the corresponding monitor
receiver can be dedicated to this task as shown in Figure 3.
Low Power Operation
These 3V devices require a nominal supply current of
0.3mA, even at V
powerdown mode). This is considerably less than the 5mA
to 11mA current required by comparable 5V RS-232 devices,
allowing users to reduce system power simply by switching
to this new family.
Pin Compatible Replacements for 5V Devices
The ICL3221E, ICL3222E, ICL3232E are pin compatible
with existing 5V RS-232 transceivers - See the “Features”
section on page 1 for details.
This pin compatibility coupled with the low I
operating supply range, make the ICL32xxE potential lower
power, higher performance drop-in replacements for existing
5V applications. As long as the ±5V RS-232 output swings are
acceptable, and transmitter input pull-up resistors aren’t
required, the IICL32xxE should work in most 5V applications.
When replacing a device in an existing 5V application, it is
acceptable to terminate C
Operating Circuits” on page 6. Nevertheless, terminate C
GND if possible, as slightly better performance results from
this configuration.
Powerdown Functionality
(Except ICL3232E)
The already low current requirement drops significantly when
the device enters powerdown mode. In powerdown, supply
current drops to 1µA, because the on-chip charge pump turns
off (V+ collapses to V
transmitter outputs three-state. Inverting receiver outputs may
or may not disable in powerdown; refer to Table 2 for details.
This micro-power mode makes these devices ideal for
battery powered and portable applications.
FIGURE 1. INVERTING RECEIVER CONNECTIONS
-25V ≤ V
RIN
R
GND
V
XIN
CC
≤ +25V
CC
= 5.5V, during normal operation (not in
CC
, V- collapses to GND), and the
3
5kΩ
to V
CC
as shown on the “Typical
GND ≤ V
R
CC
XOUT
ROUT
and wide
≤ V
June 22, 2007
CC
FN4910.19
3
to