SP3244ECY-L Exar Corporation, SP3244ECY-L Datasheet - Page 10

• Manufacturer Part Number: SP3244ECY-L
• Description: IC TXRX RS232 28TSSOP
• Manufacturer: Exar Corporation
• Type: Transceiverr

Specifications of SP3244ECY-L

• Package / Case: 28-TSSOP (0.173", 4.40mm Width)
• Number Of Drivers/receivers: 3/5
• Protocol: RS232
• Voltage - Supply: 3 V ~ 5.5 V
• Mounting Type: Surface Mount
• Maximum Operating Temperature: + 70 C
• Minimum Operating Temperature: 0 C
• Function: Transceiver
• Mounting Style: SMD/SMT
• Supply Current: 1 uA
• Supply Voltage (max): + 6 V
• Supply Voltage (min): - 0.3 V
• Logic Type: RS-232 Transceivers
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant
• Other names: 1016-1129

The SP3244E and SP3245E are 3-driver/5-re-
ceiver devices ideal for serial ports in battery-
powered, portable, or handheld applications
such as notebook or handheld computers.
SP3244E/3245E transceivers meet the EIA/
TIA-232 and ITU-T V.28/V.24 communication
protocols for reliable serial communication. The
SP3244E/3245E devices feature Exar’s propri-
etary and patented (U.S. 5,306,954) on-board
charge pump circuitry that generates ±5.5V
RS-232 voltage levels from a single +3.0V to
+5.5V power supply.
The SP3244E/3245E is an ideal choice
for power sensitive designs. With the Auto
On-Line
reduces power consumption to a 1μA supply
current whenever the transceiver is idle. In
shutdown, the internal charge pump and the
drivers will shut down. Receivers remain active
unless the device is put into manual shutdown
using the SHUTDOWN pin. This feature allows
design engineers to address power saving
concerns without major design changes.
Theory Of Operation
The SP3244E/3245E is made up of four basic
circuit blocks:
. Drivers, 2. Receivers, 3. the Exar propri-
etary charge pump, and 4. Auto On-line
circuitry.
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 infinite short circuits to
ground without degradation in reliability. These
drivers comply with the EIA/TIA-232-F and
all previous RS-232 versions. Unused driver
inputs should be connected to GND or VCC.
The SP3244E/3245E devices operate at this
typical data rate when fully loaded. The drivers
can guarantee output data rates fully loaded
with 3KΩ in parallel with 1000pF (SP3244E), or
250pF (SP3245E) ensuring compatibility with
popular PC-to-PC communication software.
The slew rate of the driver output on the
SP3244E is internally limited to a maximum
of 30V/μs in order to meet the EIA standards
®
Plus enabled the SP3244E/3245E
Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 50-668-707 • www.exar.com
®
Plus
0
The charge pumps use four external capaci-
tors to hold and transfer electrical charge. The
Exar patented design (US Patent #5,306,954)
uses a unique approach compared to older less
efficient designs. The pumps use a four–phase
voltage shifting technique to attain symmetrical
V+ and V- power supplies. An intelligent control
oscillator regulates the operation of the charge
pump to maintain the proper voltages at maxi-
mum efficiency.
Phase 1
VSS charge store and double the positive
terminals of capacitors C and C2 are charged
from VCC with their negative terminals initially
connected to ground. C+ is then connected
to ground and the stored charge from C– is
superimposed onto C2– . Since C2+ is still
connected to VCC the voltage potential across
capacitor C2 is now 2 x V
(EIA RS-232D 2..7, Paragraph 5). The slew
rate of SP3245E is not limited to enable higher
speed data transfers. The transition of the
loaded output from HIGH to LOW also meets
the monotonic signal transition requirements of
the standard.
Receivers
The receivers convert EIA/TIA-232 signal
levels to TTL or CMOS logic output levels. Re-
ceivers remain active unless the device is put
into manual shutdown using the SHUTDOWN
pin. The non-inverted output of Receiver
2 (R2OUT) will continue to be active in all
modes, including shutdown.
Since receiver input is usually from a transmis-
sion line where long cable lengths and system
interference can degrade the signal, the inputs
have a typical hysteresis margin of 500mV.
This ensures that the receiver is virtually im-
mune to noisy transmission lines. Should an
input be left unconnected, an internal 5KΩ pull-
down resistor to ground will commit the output
of the receiver to a HIGH state.
Highly Efficient Charge Pump
The charge pump is used to generate positive
and negative signal voltages for the RS-232
drivers. This enables fully compliant RS-232
and V.28 signals from a single 3.0 or 5.5V
power supply.
SP3244E_SP3245E_00_2509
cc
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DESCRIPTION