SP303 Datasheet, PDF (5/8 Pages) Sipex Corporation – RS232/AppleTalk TM Serial Transceiver

SUPPLY
+5V +12V –12V
28 1 15
V_CC V_DD V_EE
T_INA1 ²³
T₁
6
T_OUTA1
T_INA2 ²⁴
T₂
5
T_OUTA2
20
T_INB1
T₃
9
T_OUTB1
T_INB2 ¹⁹
T₄
26 ^SP303
R_OUTA1
R₁
27
R_OUTA2
R₂
R_OUTB1 ¹⁷
R₃
16
R_OUTB2
R₄
10 _TOUTB2
3
R_INA1
2
R_INA2
12
R_INB1
13
R_INB2
14 _{GND SELECT}
A
B
7
8
Figure 1. RS232 Operating Mode
differential, while the handshake-out and hand-
shake-in signals are single–ended. The SP303
does not have the extra GPI (General Purpose
Input). All drivers and receivers can operate at
data rates up to 1 Mbps. The differential driver
used for transmitting data signals is equipped
with a tri-state function. When the TxEN pin is
brought low, the differential driver is enabled;
when it is high, the driver outputs are tri–stated.
The tri–state function does not affect any other
driver in either mode of operation.
One SP303 can significantly reduce the board
space necessary for a similar discrete solution
offering both RS-232 and AppleTalk interfaces.
Due to the space savings, the SP303 can provide
multi-mode interfacing to equipment such as
printers or modems without sacrificing addi-
tional board space or cost. This allows the OEM
to offer more flexible interface capabilities with-
out additional material costs.
The SP303 is available in a 28–pin SOIC pack-
age for operation over the commercial tempera-
ture range.
APPLICATION EXAMPLE
RS-232 MODE SERIAL INTERFACE
Figure 3 shows the SP303CT used in a dual
serial port application which allows both
RS-232 and Macintosh™ AppleTalk™ Mode
interfaces. With SEL A and SEL B low, the port
can be configured for RS-232. In this mode, the
SP303CT is set up for 4 drivers and 4 receivers.
The transmitter enable pin (pin22) has no effect
in this mode.
The RFI filters shown are optional depending
upon the FCC requirements of the system. The
SP303CT has internal slew rate limiting, which
keeps the RS-232 slew rate <30V/µs. Since the
SUPPLY
+5V +12V –12V
28 1 15
7 ^{VCC VDD VEE}
SELECT A
8 _{SELECT B}
23
T_INA1
T₁
22
T_XEN
20
T_INB1
T₂
SP303
26
R_OUTA1
R₁
5
T_OUTA2
6
T_OUTA1
9 _TOUTB1
10 _TOUTB2
2 _RINA2
3 _RINA1
17
R_OUTB1
R₂
14
GND
12 _RINB1
13
Figure 2. Macintosh™ AppleTalk™ Operating Mode
Corporation
SIGNAL PROCESSING EXCELLENCE
73