■ Meets true EIA/TIA-232-F Standards
from a +3.0V to +5.5V power supply
■ Minimum 120kbps Data Rate Under Full
Load
■ 1µA Low Power Shutdown with
Receivers active (SP3222E)
■ Interoperable with RS-232 down to a
+2.7V power source
■ Enhanced ESD Specications:
+15kV Human Body Model+15kV IEC61000-4-2 Air Discharge+8kV IEC61000-4-2 Contact Discharge
SP3222E/SP3232E
Now Available in Lead Free Packaging
Note: See page 6 for other pinouts
DESCRIPTION
The SP3222E/SP3232E series is an RS-232 transceiver solution intended for portable or
hand-held applications such as notebook or palmtop computers. The SP3222E/SP3232Eseries has a high-efciency, charge-pump power supply that requires only 0.1µF capacitors in 3.3V operation. This charge pump allows the SP3222E/SP3232E series to deliver
true RS-232 performance from a single power supply ranging from +3.0V to +5.5V. The
SP3222E/SP3232E are 2-driver/2-receiver devices. This series is ideal for portable or
hand-held applications such as notebook or palmtop computers. The ESD tolerance of the
SP3222E/SP3232E devices are over +/-15kV for both Human Body Model and IEC61000-4-2 Air discharge test methods. The SP3222E device has a low-power shutdown mode where
the devices' driver outputs and charge pumps are disabled. During shutdown, the supply
current falls to less than 1µA.
These are stress ratings only and functional operation
of the device at these ratings or any other above those
indicated in the operation sections of the specications
below is not implied. Exposure to absolute maximum
rating conditions for extended periods of time may
affect reliability and cause permanent damage to the
device.
VCC.......................................................-0.3V to +6.0V
V+ (NOTE 1).......................................-0.3V to +7.0V
V- (NOTE 1)........................................+0.3V to -7.0V
Unless otherwise noted, the following performance characteristics apply for VCC = +3.3V, 120kbps data rate, all
drivers loaded with 3kΩ, 0.1µF charge pump capacitors, and T
= +25°C.
AMB
Figure 1. Transmitter Output Voltage vs Load
Capacitance for the SP3222E and SP3232E
Figure 3. Supply Current VS. Load Capacitance
when Transmitting Data
Figure 2. Slew Rate vs Load Capacitance for the
SP3222E and SP3232E
hand-held applications such as notebook or
palmtop computers. The SP3222E/SP3232E
devices feature Exar's proprietary on-board
charge pump circuitry that generates ±5.5V
for RS-232 voltage levels from a single
+3.0V to +5.5V power supply. This series is
ideal for +3.3V-only systems, mixed +3.3V
to +5.5V systems, or +5.0V-only systems
that require true RS-232 performance. The
SP3222E/SP3232E devices can operate
at a typical data rate of 235kbps when fully
loaded.
The SP3222E and SP3232E are 2-driver/2-
receiver devices ideal for portable or handheld applications. The SP3222E features a
1µA shutdown mode that reduces power
consumption and extends battery life in portable systems. Its receivers remain active in
shutdown mode, allowing external devices
such as modems to be monitored using only
1µA supply current.
THEORY OF OPERATION
The SP3222E/SP3232E series is made up
of three basic circuit blocks:
1. Drivers
2. Receivers
3. The Exar proprietary charge pump
Drivers
The drivers are inverting level transmitters
that convert TTL or CMOS logic levels to
+5.0V EIA/TIA-232 levels with an inverted
sense relative to the input logic levels.
Typically, the RS-232 output voltage swing
is +5.4V with no load and +5V minimum fully
loaded. The driver outputs are protected
against innite short-circuits to ground without degradation in reliability. Driver outputs
will meet EIA/TIA-562 levels of +/-3.7V with
supply voltages as low as 2.7V.
120kbps fully loaded with 3kΩ in parallel
with 1000pF, ensuring compatability with
PC-to-PC communication software.
The slew rate of the driver is internally limited
to a maximum of 30V/µs in order to meet the
EIA standards (EIA RS-232D 2.1.7, Para-
graph 5). The transition of the loaded output
from HIGH to LOW also meet the monotonicity requirements of the standard.
Figure 8 shows a loopback test circuit
used to test the RS-232 Drivers. Figure
9 shows the test results of the loopback
circuit with all drivers active at 120kbps
with RS-232 loads in parallel with a
1000pF capacitor. Figure 10 shows the
test results where one driver was active
at 235kbps and all drivers loaded with an
RS-232 receiver in parallel with 1000pF
capacitors. A solid RS-232 data transmis-
sion rate of 120kbps provides compatibility
with many designs in personal computer
peripherals and LAN applications.
The SP3222E driver's output stages are
turned off (tri-state) when the device is in
shutdown mode. When the power is off, the
SP3222E device permits the outputs to be
driven up to +/-12V. The driver's inputs do
not have pull-up resistors. Designers should
connect unused inputs to Vcc or GND.
In the shutdown mode, the supply current
falls to less than 1µA, where SHDN = LOW.
When the SP3222E device is shut down,
the device's driver outputs are disabled (tristated) and the charge pumps are turned off
with V+ pulled down to Vcc and V- pulled to
GND. The time required to exit shutdown is
typically 100µs. Connect SHDN to Vcc if the
shutdown mode is not used.
8
Page 9
Figure 8. SP3222E/SP3232E Driver Loopback Test
3
1
2
T
T
T
T[]
T1 IN
T1 OUT
R1 OUT
Ch1
Ch3
5.00V
Ch2
5.00V M 2.50 µs
Ch1
0V
5.00V
3
1
2
T
T
T
T[]
T1 IN
T1 OUT
R1 OUT
Ch1
Ch3
5.00V
Ch2
5.00V M 5.00µs
Ch1
0V
5.00V
SP3222E
SP3232E
GND
TxIN
TxOUT
C1+
C1-
C2+
C2-
V+
V-
V
CC
0.1µF
0.1µF
0.1µF
+
C2
C5
C1
+
+
C3
C4
+
+
0.1µF
0.1µF
LOGIC
INPUTS
V
CC
5kΩ
RxIN
RxOUT
LOGIC
OUTPUTS
EN*
*SHDN
1000pF
V
CC
* SP3222E only
Circuit
DESCRIPTION
Receivers
The Receivers convert EIA/TIA-232 levels
to TTL or CMOS logic output levels. The
SP3222E receivers have an inverting tri-state
output. These receiver outputs (RxOUT)
are tri-stated when the enable control EN =
HIGH. In the shutdown mode, the receivers
can be active or inactive. EN has no effect on
TxOUT. The truth table logic of the SP3222E
driver and receiver outputs can be found in
Table 2.
SHDNENTxOUTRxOUT
00Tri-stateActive
01Tri-state Tri-state
10ActiveActive
11ActiveTri-state
Table 2. SP3222E Truth Table Logic for Shutdown
and Enable Control
Since receiver input is usually from a transmission line where long cable lengths and
system interference can degrade the signal,
the inputs have a typical hysteresis margin
design (U.S. 5,306,954) and uses a unique
approach compared to older less-efcient
designs. The charge pump still requires four
external capacitors, but uses a four-phase
voltage shifting technique to attain symmetrical 5.5V power supplies. The internal
power supply consists of a regulated dual
charge pump that provides output voltages
of +/-5.5V regardless of the input voltage
(Vcc) over the +3.0V to +5.5V range.
9
Page 10
DESCRIPTION
In most circumstances, decoupling the
power supply can be achieved adequately
using a 0.1µF bypass capacitor at C5 (refer
to gures 6 and 7). In applications that are
sensitive to power-supply noise, decouple
Vcc to ground with a capacitor of the same
value as charge-pump capacitor C1. Physically connect bypass capcitors as close to
the IC as possible.
The charge pump operates in a discontinu-
ous mode using an internal oscillator. If the
output voltages are less than a magnitude
of 5.5V, the charge pump is enabled. If the
output voltages exceed a magnitude of 5.5V,
the charge pump is disabled. This oscillator
controls the four phases of the voltage shifting. A description of each phase follows.
Phase 1
— VSS charge storage — During this phase
of the clock cycle, the positive side of capacitors C1 and C2 are initially charged to VCC.
+
C
is then switched to GND and the charge
l
–
in C
is transferred to C
1
nected to VCC, the voltage potential across
–
. Since C
2
+
is con-
2
capacitor C2 is now 2 times VCC.
Phase 2
— VSS transfer — Phase two of the clock
connects the negative terminal of C2 to the V
storage capacitor and the positive terminal of
SS
C2 to GND. This transfers a negative generated voltage to C3. This generated voltage is
regulated to a minimum voltage of -5.5V.
Simultaneous with the transfer of the voltage to C3, the positive side of capacitor C1
is switched to VCC and the negative side is
connected to GND.
Phase 4
— VDD transfer — The fourth phase of
theclockconnects the negative terminal
of C2 to GND, and transfers this positive
generated voltage across C2 to C4, the
VDD storage capacitor. This voltage is
regulated to +5.5V. At this voltage, the internal oscillator is disabled. Simultaneous
with the transfer of the voltage to C4, the
positive side of capacitor C1 is switched
to VCC and the negative side is connected to GND, allowing the charge
pump cycle to begin again. The charge
pump cycle will continue as long as the
operational conditions for the internal
oscillator are present.
Since both V+ and V– are separately generated from VCC, in a no–load condition V+
and V– will be symmetrical. Older charge
pump approaches that generate V– from
V+ will show a decrease in the magnitude
of V– compared to V+ due to the inherent
inefciencies in the design.
The clock rate for the charge pump typically
operates at greater than 250kHz. The external capacitors can be as low as 0.1µF with
a 16V breakdown voltage rating.
Phase 3
— VDD charge storage — The third phase of
the clock is identical to the rst phase — the
charge transferred in C1 produces –VCC in
the negative terminal of C1, which is applied
to the negative side of capacitor C2. Since
output and receiver input pins. The ESD
structure is improved over our previous
family for more rugged applications and
environments sensitive to electro-static
discharges and associated transients. The
improved ESD tolerance is at least +15kV
without damage nor latch-up.
DESCRIPTION
the system is required to withstand an amount
of static electricity when ESD is applied to
points and surfaces of the equipment that
are accessible to personnel during normal
usage. The transceiver IC receives most
of the ESD current when the ESD source is
applied to the connector pins. The test circuit
for IEC61000-4-2 is shown on Figure 17.
There are two methods within IEC61000-4-2,
the Air Discharge method and the Contact
Discharge method.
There are different methods of ESD testing
applied:
a) MIL-STD-883, Method 3015.7
b) IEC61000-4-2 Air-Discharge
c) IEC61000-4-2 Direct Contact
The Human Body Model has been the
generally accepted ESD testing method
for semi-conductors. This method is also
specied in MIL-STD-883, Method 3015.7
for ESD testing. The premise of this ESD test
is to simulate the human body’s potential to
store electro-static energy and discharge it
to an integrated circuit. The simulation is
performed by using a test model as shown
in Figure 16. This method will test the IC’s
capability to withstand an ESD transient
during normal handling such as in manu-
facturing areas where the ICs tend to be
handled frequently.
The IEC-61000-4-2, formerly IEC801-2, is
generally used for testing ESD on equipment
and systems. For system manufacturers,
they must guarantee a certain amount of ESD
protection since the system itself is exposed
to the outside environment and human pres-
ence. The premise with IEC61000-4-2 is that
With the Air Discharge Method, an ESD
voltage is applied to the equipment under
test (EUT) through air. This simulates an
electrically charged person ready to connect
a cable onto the rear of the system only to
nd an unpleasant zap just before the person
touches the back panel. The high energy
potential on the person discharges through
an arcing path to the rear panel of the system
before he or she even touches the system.
This energy, whether discharged directly or
through air, is predominantly a function of the
discharge current rather than the discharge
voltage. Variables with an air discharge such
as approach speed of the object carrying the
ESD potential to the system and humidity
will tend to change the discharge current.
For example, the rise time of the discharge
current varies with the approach speed.
The Contact Discharge Method applies the
ESD current directly to the EUT. This method
was devised to reduce the unpredictability
of the ESD arc. The discharge current rise
time is constant since the energy is directly
transferred without the air-gap arc. In situations such as hand held systems, the ESD
charge can be directly discharged to the
equipment from a person already holding
the equipment. The current is transferred
on to the keypad or the serial port of the
equipment directly and then travels through
the PCB and nally to the IC.
The circuit models in Figures 16 and 17 rep-
resent the typical ESD testing circuit used for
all three methods. The CS is initially charged
with the DC power supply when the rst
switch (SW1) is on. Now that the capacitor
is charged, the second switch (SW2) is on
while SW1 switches off. The voltage stored
in the capacitor is then applied through RS,
the current limiting resistor, onto the device
under test (DUT). In ESD tests, the SW2
switch is pulsed so that the device under
test receives a duration of voltage.
For the Human Body Model, the current
limiting resistor (RS) and the source capacitor
(CS) are 1.5kΩ an 100pF, respectively. For
IEC-61000-4-2, the current limiting resistor
(RS) and the source capacitor (CS) are 330Ω
an 150pF, respectively.
The higher CS value and lower RS value in
the IEC61000-4-2 model are more stringent
than the Human Body Model. The larger
storage capacitor injects a higher voltage
to the test point when SW2 is switched on.
The lower current limiting resistor increases
the current charge onto the test point.
Figure 18. ESD Test Waveform for IEC61000-4-2
DEVICE PIN HUMAN BODY IEC61000-4-2
TESTED MODEL Air Discharge Direct Contact Level
12/08/101.0.0Convert to Exar Format and update ordering information.
03/14/131.0.1Correct type error to driver Transition-Region Slew Rate
conditions.
Notice
EXAR Corporation reserves the right to make changes to any products contained in this publication in order to improve design, performance or reliability. EXAR Corporation assumes no representation that the circuits are free of patent infringement. Charts and schedules contained herein are
only for illustration purposes and may vary depending upon a user's specic application. While the information in this publication has been carefully
checked; no responsibility, however, is assumed for inaccuracies.
EXAR Corporation does not recommend the use of any of its products in life support applications where the failure or malfunction of the product can
reasonably be expected to cause failure of the life support system or to signicantly affect its safety or effectiveness. Products are not authorized for
use in such applications unless EXAR Corporation receives, in writting, assurances to its satisfaction that: (a) the risk of injury or damage has been
minimized ; (b) the user assumes all such risks; (c) potential liability of EXAR Corporation is adequately protected under the circumstances.
Copyright 2013 EXAR Corporation
Datasheet March 2013
For technical questions please email Exar's Serial Technical Support group at: [email protected]
Reproduction, in part or whole, without the prior written consent of EXAR Corporation is prohibited.