SP3243 SIPEX [Sipex Corporation], SP3243 Datasheet - Page 10

• Manufacturer Part Number: SP3243
• Description: Intelligent +3.0V to +5.5V RS-232 Transceivers
• Manufacturer: SIPEX [Sipex Corporation]

DESCRIPTION
The SP3223 and SP3243 transceivers meet the
EIA/TIA-232 and ITU-T V.28/V.24 communica-
tion protocols and can be implemented in bat-
tery-powered, portable, or hand-held applica-
tions such as notebook or palmtop computers.
The SP3223 and SP3243 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 SP3223 and SP3243
devices
a typical data rate of 235kbps fully loaded.
The SP3223 is a 2-driver/2-receiver device, and
the SP3243 is a 3-driver/5-receiver device
ideal for portable or hand-held applications.
The SP3243 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 V
disconnected.
Figure 11. Interface Circuitry Controlled by Micropro-
cessor Supervisory Circuit
Rev. 6/30/03
RESET
Serial µC
UART
Supervisor
or
µP
IC
V IN
can
RTS
C2
TxD
DTR
RxD
C5
C1
CTS
DCD
DSR
RI
+
+
+
V
0.1µF
0.1µF
0.1µF
CC
24
14
13
12
20
19
16
15
22
21
28
18
17
23
1
2
C1+
C1-
C2+
C2-
T
T
R
R
R
T
R
R
SHUTDOWN
ONLINE
STATUS
R
1
2
3
2
1
2
3
4
IN
IN
OUT
5
IN
OUT
OUT
OUT
OUT
OUT
operate
SP3243
V
V
GND
CC
CC
26
25
5KΩ
5KΩ
5KΩ
5KΩ
5KΩ
T
T
T
1
2
3
R
R
R
R
R
OUT
OUT
OUT
5
V+
1
2
3
4
CC
V-
IN
IN
IN
IN
IN
SP3223 +3.0V to +5.5V RS-232 Transceivers
10
4
27
3
11
5
6
7
8
9
may be
C3
C4
RS-232
OUTPUTS
+
+
RS-232
INPUTS
0.1µF
0.1µF
at
10
The SP3223 and SP3243 series is an ideal choice
for power sensitive designs. The SP3223 and
SP3243 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 conditions, the internal
charge pump and the drivers will be shut down.
Otherwise, the system automatically comes
online. This feature allows design engineers to
address power saving concerns without major
design changes.
THEORY OF OPERATION
The SP3223 and SP3243 series is made up
of four basic circuit blocks:
1. Drivers, 2. Receivers, 3. the Sipex proprietary
charge pump, and 4. AUTO ON-LINE
cuitry.
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
should be connected to GND or V
The drivers can guarantee a data rate of 120Kbps
fully loaded with 3KΩ in parallel with 1000pF,
ensuring compatibility with PC-to-PC commu-
nication software.
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.
© Copyright 2003 Sipex Corporation
CC
.
®
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®