SP3223E_06 Datasheet, PDF (10/23 Pages) Sipex Corporation – Intelligent +3.0V to +5.5V RS-232 Transceivers

DEVICE: SP3223
SHUTDOWN
EN
0
0
T_XOUT
High Z
0
1
High Z
1
0
Active
1
1
Active
R_XOUT
Active
High Z
Active
High Z
Table 2. SHUTDOWN and EN Truth Tables
Note: In AUTO ON-LINE^® Mode where ONLINE =
GND and SHUTDOWN = V_CC, the device will shut down
if there is no activity present at the Receiver inputs.
Receivers
The receivers convert ±5.0V EIA/TIA-232
levels to TTL or CMOS logic output levels.
Receivers have an inverting output that can be
disabled by using the EN pin.
Receivers are active when the AUTO ON-LINE^®
circuitry is enabled or when in shutdown.
During the shutdown, the receivers will continue
to be active. If there is no activity present at the
receivers for a period longer than 100µs or when
SHUTDOWN is enabled, the device goes into a
standby mode where the circuit draws 1µA.
Driving EN to a logic HIGH forces the outputs of
the receivers into high-impedance. The truth
table logic of the SP3223 driver and receiver
outputs can be found in Table 2.
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 300mV. This
ensures that the receiver is virtually immune to
noisy transmission lines. Should an input be left
unconnected, an internal 5KΩ pulldown resistor
to ground will commit the output of the receiver
to a HIGH state.
+3V to +5V
+
C5 0.1µF
+
C1 0.1µF
+
C2 0.1µF
2 _C1+
4 C1-
5 C2+
6 C2-
TTL/CMOS
INPUTS
T₁IN
T_XIN
19
VCC
V+ ³
SP3223
V- ⁷
T₁OUT
T_XOUT
+
C3 0.1µF
C4 0.1µF
+
TTL/CMOS
OUTPUTS
R₁OUT
R₁IN
5KΩ
VCC
To µP Supervisor
Circuit
R_XOUT
1 _EN
R_XIN
5KΩ
20 _SHUTDOWN
14 _ONLINE
11 _STATUS
GND
18
1000pF
1000pF
Figure 14. Loopback Test Circuit for RS-232 Driver
Data Transmission Rates
Charge Pump
The charge pump is a Sipex–patented design
(U.S. 5,306,954) and uses a unique approach
compared to older less–efficient 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
T1 IN
T1 OUT
R1 OUT
Date: 10/06/06
Figure 15. Loopback Test Circuit result at 235Kbps
(All Drivers Fully Loaded)
SP3223 +3.0V to +5.5V RS-232 Transceivers
10
© Copyright 2006 Sipex Corporation