DESCRIPTION
TheSP3223EBandSP3243EBtransceiversmeet
the EIA/TIA-232 and ITU-T V.28/V.24 com-
munication protocols and can be implemented
in battery-powered, portable, or hand-held ap-
plications such as notebook or palmtop comput-
ers. The SP3223EB and SP3243EB devices
feature Sipex's proprietary 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
SP3223EB and SP3243EB devices can operate
at a data rate of 250kbps fully loaded.
The SP3223EB and SP3243EB series is an ideal
choice for power sensitive designs. The
SP3223EB and SP3243EB devices feature
®
AUTO ON-LINE circuitry which reduces the
power supply drain to a 1µA supply current. In
many portable or hand-held applications, an RS-
232 cable can be disconnected or a connected
peripheral can be turned off. Under these condi-
tions, the internal charge pump and the drivers
will be shut down. Otherwise, the system auto-
matically comes online. This feature allows de-
sign engineers to address power saving concerns
without major design changes.
The SP3223EB is a 2-driver/2-receiver device,
and the SP3243EB is a 3-driver/5-receiver de-
viceidealforportableorhand-held applications.
The SP3243EB includes one complementary
always-active receiver that can monitor an
external device (such as a modem) in shutdown.
This aids in protecting the UART or serial
controller IC by preventing forward biasing
of the protection diodes where VCC may be
disconnected.
THEORY OF OPERATION
TheSP3223EBandSP3243EBseriesismadeup
of four basic circuit blocks:
1. Drivers,
2. Receivers,
3. the Sipex proprietary 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-232F and all
previous RS-232 versions. Unused driver inputs
V
CC
+
+
26
0.1µF
0.1µF
C5
C1
V
CC
28
27
3
C1+
V+
+
+
C3
C4
0.1µF
0.1µF
24
1
C1-
C2+
SP3243EB
V-
+
C2
0.1µF
2
14
13
C2-
T
1OUT
T1IN
9
TxD
RTS
DTR
T2OUT
T
2IN
3IN
10
11
RS-232
OUTPUTS
T
3OUT
T
12
R2OUT
20
19
UART
or
Serial C
R1IN
R1OUT
4
5
RxD
CTS
5KΩ
5KΩ
R
2IN
R2OUT
18
17
16
15
should be connected to GND or VCC
.
R3OUT
R3IN
DSR
DCD
RI
6
7
8
RS-232
INPUTS
5KΩ
5KΩ
5KΩ
R4OUT
R
4IN
5IN
The drivers can guarantee a data rate of 250kbps
fully loaded with 3kΩ in parallel with 1000pF,
ensuring compatibility with PC-to-PC commu-
nication software.
R5OUT
R
VCC
22
23
SHUTDOWN
ONLINE
21
STATUS
GND
25
P
Supervisor
IC
V
RESET
IN
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 2.1.7,
Paragraph 5). The transition of the loaded
output from HIGH to LOW also meets the
monotonicity requirements of the standard.
Figure 16. Interface Circuitry Controlled by Micropro-
cessor Supervisory Circuit
Date: 6/2/04
SP3223EB/3243EB +3.0V to +5.5V RS-232 Transceivers
© Copyright 2004 Sipex Corporation
10
SIPEX [ SIPEX CORPORATION ]
