SP3203ECY-L Datasheet, PDF (7/16 Pages) Exar Corporation – 3V RS-232 Serial Transceiver with Logic Selector and 15kV ESD Protection

DESCRIPTION
The SP3203E is a 3-driver/2-receiver device
ideal for portable or handheld applications.
The SP3203E transceivers meet the EIA/
TIA-232 and ITU-T V.28/V.24 communication
protocols and can be implemented in battery-
powered, portable, or handheld applications
such as notebook or palmtop computers,
PDA's and cell phones. The SP3203E device
features Exar's proprietary and patented
(U.S.‑‑ 5,306,954) on-board charge pump
circuitry that generates ±5.5V RS-232 volt-
Figure 2 shows a loopback test circuit used
to test the RS-232 Drivers. Figure 3 shows
the test results with all drivers active at
120kbps with typical RS-232 loads in parallel
with a 1000pF capacitors. Figure 4 shows
the test results where one driver was active
at 250kbps and all three drivers loaded with
an RS-232 receiver in parallel with a 1000pF
capacitor. The transmitter inputs do not have
pull-up resistors. Connect unused inputs to
ground or V_L.
age levels from a single +3.0V to +5.5V
power supply. The SP3203E can operate at
Receivers
a minimum data rate of 250kbps.
The receivers convert ±5.0V EIA/TIA-232
levels to TTL or CMOS logic output levels.
THEORY OF OPERATION
Receivers are disabled when in shutdown.
The SP3203E is made up of four basic
circuit blocks:
1. Drivers, 2. Receivers, 3. The Exar propri-
The truth table logic of the SP3203E driver
and receiver outputs can be found in Table
1.
etary charge pump, and 4. V_L circuitry.
Since receiver input is usually from a trans-
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
mission 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 immune 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.
in reliability. These drivers comply with the
EIA-TIA-232F and all previous RS-232 ver-
sions. The driver output stages are turned
Charge Pump
off (High Impedance) when the device is in The charge pump is a patented design (U.S.
shutdown mode.
5,306,954) and uses a unique approach
compared to older less–efficient designs.
The drivers can guarantee output data rates
fully loaded with 3kΩ in parallel with 1000pF,
ensuring compatibility with PC-to-PC com-
munication software.
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
The slew rate of the driver output is internally
limited to a maximum of 30V/µs in order
to meet the EIA standards (EIA RS-232D
pump that provides output voltages of
+/-5.5V regardless of input voltage (V_CC)
over the +3.0V to +5.5V range. This
is important to maintain compliant RS-
2.1.7, Paragraph 5). The transition of the 232 levels regardless of power supply
loaded output from HIGH to LOW also fluctuations.
meets the monotonicity requirements of
the standard.
Exar Corporation 48720 Kato Road, Fremont CA, 94538 • [phone] • www.exar.com
SP3203E_100_120810