
Rev. 6/30/03
SP3223H +3.0V to +5.5V RS-232 Transceivers
10
Copyright 2003 Sipex Corporation
DESCRIPTION
The
SP3223H
and
SP3243H
transceivers meet
the EIA/TIA-232 and ITU-T V.28/V.24 commu-
nication
protocols
implemented in battery-powered, portable, or
hand-held applications such as notebook or
palmtop computers. The
SP3223H
and
SP3243H
devices feature
Sipex's
proprietary and patented
(U.S.-- 5,306,954) on-board charge pump cir-
cuitry that generates +5.5V RS-232 voltage lev-
els from a single +3.0V to +5.5V power supply.
The
SP3223H
and
SP3243H
devices can oper-
ate at a data rate of 460Kbps fully loaded.
and
can
be
The
SP3223H
is a 2-driver/2-receiver device,
and the
SP3243H
is a 3-driver/5-receiver device,
ideal for portable or hand-held applications. The
SP3243H
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
CC
may be
disconnected.
The
SP3223H
and
SP3243H
series is an ideal
choice for power sensitive designs. The
SP3223H
and
SP3243H
devices feature
Auto-Online
cir-
cuitry which reduces the power supply drain to a
1
μ
A supply current. In many portable or hand-
held applications, an RS-232 cable can be dis-
connected or a connected peripheral can be turned
off. Under these conditions, the internal charge
pump and the drivers will be shut down. Other-
wise, the system automatically comes online.
This
feature
engineers to address power saving concerns
without major design changes.
allows
design
THEORY OF OPERATION
The
SP3223H
and
SP3243H
series is made up of
four basic circuit blocks: 1. Drivers,
2. Receivers, 3. the Sipex proprietary charge
pump, and 4.
Auto-Online
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.
The drivers can guarantee a data rate over
460Kbps fully loaded with 3K
in parallel with
1000pF, ensuring compatibility with PC-to-PC
communication software.
The slew rate of the driver output is internally
limited to a maximum of 30V/
μ
s 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 11. Interface Circuitry Controlled by Micropro-
cessor Supervisory Circuit
SP3243H
28
24
2
1
27
3
26
5K
5K
5K
5K
5K
GND
C1+
C1-
C2+
C2-
T
1
IN
V+
V-
V
CC
14
13
12
20
19
18
17
16
15
0.1
μ
F
0.1
μ
F
0.1
μ
F
+
C2
C5
C1
+
+
C3
C4
+
+
0.1
μ
F
0.1
μ
F
9
10
11
4
5
6
7
8
RS-232
RS-232
23
22
21
V
CC
25
R
1
OUT
R
1
IN
T
2
OUT
R
2
OUT
T
2
IN
T
3
IN
T
3
OUT
T
1
OUT
R
2
IN
R
3
IN
R
4
IN
R
5
IN
R
2
OUT
R
3
OUT
R
4
OUT
R
5
OUT
ONLINE
SHUTDOWN
STATUS
UART
or
Serial
μ
C
SupeP
IC
TxD
RTS
DTR
RxD
CTS
DSR
DCD
RI
V
CC
VIN
RESET