sp304ct Exar Corporation, sp304ct Datasheet - Page 4

• Manufacturer Part Number: sp304ct
• Description: Rs-232/rs-422 Line Drivers/receivers
• Manufacturer: Exar Corporation

80
PIN ASSIGNMENTS
FEATURES…
The SP304 is a proprietary single-chip device
that contain both RS-232 and RS-422 protocol
line drivers and receivers. It is pin–for–pin com-
patible with the Sipex SP302. Like the SP302,
its configuration may be changed at any time by
logic levels on two control lines. In any configu-
ration, the SP304 fully meets the requirements
of both the EIA RS-232D and RS-422 data
communication standards. The SP304 enhance-
ments include improved isolation from external
signals and a true high–impedance driver output
in the loopback test mode, and no power up
sequence requirements.
The RS-232 line driver circuits convert TTL
logic level inputs into inverted RS-232 output
signals. The RS-422 line drivers convert TTL
logic levels into RS-422 differential output sig-
nals. The RS-422 line driver outputs feature
high source and sink current capability. All line
drivers are internally protected against short
circuits on their outputs.
The RS-232 receivers convert the EIA RS-232
input signals to inverted TTL output logic lev-
els. The RS-422 receivers convert the EIA RS-
422 differential input signals into non-inverted
TTL output logic levels. Receiver input filtering
provides excellent high frequency noise immu-
nity. Input pulses with widths less than 1 s are
completely ignored. The RS-232 receivers have
the additional feature of voltage hysteresis, which
helps eliminate spurious output transitions that
V
SELECT A 6
SELECT B 7
DD
(+12V) 1
GND 12
RIB
RIB
TOA
TOA
TOB
TOB
RIA
RIA
1
2
2
1
2
1
1
2
10
11
2
3
4
5
8
9
24 V
23 ROA
22 ROA
21 TIA
20 TIA
19 LB
18 N.C.
17 TIB
16 TIB
15 ROB
14 ROB
13 V
CC
EE
2
1
1
2
(-12V)
(+5V)
2
1
1
2
might result from low amplitude noise voltages
during slower-speed signal transitions.
A loopback test mode is provided that puts the
driver outputs to a high impedance tri-state
level, and routes the driver outputs to their
associated receiver inputs. In this configuration,
the signal path is non-inverting from the TTL
driver input to the receiver TTL output. This
operating mode allows the controlling system to
perform diagnostic self-test of the RS-232/
RS-422 driver/receiver circuitry at speeds up to
3,000 bits per second. In the loopback mode a
ceiver inputs with no interference to the loopback
test. In addition, the driver outputs are in a true
high–impedance state during loopback.
The SP304 is available in 24-pin single width
(0.300") plastic DIP and 28-pin SOIC packages,
for operation over the commercial and indus-
trial temperature ranges.
USING THE SP304
POWER SUPPLIES
The SP304 requires 12V and +5V for full
RS-232 and RS-422 operation. The 12V sup-
plies set up the RS-232 9V voltage swings, and
the +5V is used for the internal logic that for-
mats the communications mode and controls the
loopback function. The supply voltages can be
decreased to as low as 7V for V
13.2V input range may be applied to the re-
V
SELECT A 7
SELECT B 8
DD
(+12V) 1
TOB
GND 14
RIB
RIB
TOA
TOA
TOB
N.C. 11
RIA
RIA
N.C. 4
2
1
2
2
1
2
1
1
10
12
13
2
3
5
6
9
DD
28 V
27 ROA
26 ROA
25 N.C.
24 TIA
23 TIA
22 LB
21 N.C.
20 TIB
19 TIB
18 N.C.
17 ROB
16 ROB
15 V
SIGNAL PROCESSING EXCELLENCE
and V
CC
EE
2
1
1
2
(-12V)
(+5V)
2
1
1
2
Corporation
EE
, and