ISL3333EVAL1Z Intersil, ISL3333EVAL1Z Datasheet - Page 14

• Manufacturer Part Number: ISL3333EVAL1Z
• Description: EVAL BOARD 1 FOR ISL3333
• Manufacturer: Intersil

Specifications of ISL3333EVAL1Z

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Typical Application
RS-232 to RS-485 Converter
The ISL3332, ISL3333 are ideal for implementing a single IC
2-wire (Tx Data, Rx Data) protocol converter, because each
port can be programmed for a different protocol. Figure 8
illustrates the simple connections to create a single
transceiver RS-232 to RS-485 converter. Depending on the
RS-232 data rate, using an RS-422 bus as an RS-232
“extension cord” can extend the transmission distance up to
4000’ (1220m). A similar circuit on the other end of the cable
completes the conversion to/from RS-232.
Tx/Rx
RS-232 OUT
RS-485 OUT
FIGURE 8. SINGLE IC RS-232 TO RS-485 CONVERTER
RxD
RS-485 IN
RS-232 IN
TxD
+3.3V
RXEN *
0.1µF
0.1µF
* QFN ONLY
V
NC
NC
RA
DE
DY
C
C
CC
1
2
NOTE: PINOUT FOR SSOP
ISL333X
+
+
+ 0.1µF
28
27
11
10
13
12
1
2
4
5
6
7
8
D
9
SEL1
R
C1+
C1-
C2+
C2-
B1
SEL2
A1
Y1
Z1
Y2
Z2
A2
B2
5kΩ
5kΩ
GND
V
+3.3V
B
A
Y
Z
CC
GND
V
14
CC
D
14
26
R
R
R
ON/OFF
D
D
R
R
D
D
R
DE2 18
D
V+
A1
B1
Y1
Z1
A2
Y2
V-
+
R
FIGURE 9. TYPICAL HALF DUPLEX RS-485 NETWORK
3
15
24
0.1µF
25
22
23
20
19
17
T
NC
+ C
+
0.1µF
C
0.1µF
V
+5V
V
0.1µF
3
4
CC
CC
GENERIC 1/2 DUPLEX 485 XCVR
V
ISL3332, ISL3333
CC
RO
R
RE
B/Z
DE
Detailed Description
Each of the two ISL333X ports supports dual protocols:
RS-485/422, and RS-232. RS-485 and RS-422 are differential
(balanced) data transmission standards for use in high speed
(up to 20Mbps) networks, or long haul and noisy
environments. The differential signaling, coupled with
RS-485’s requirement for an extended common mode range
(CMR) of +12V to -7V make these transceivers extremely
tolerant of ground potential differences, as well as voltages
induced in the cable by external fields. Both of these effects
are real concerns when communicating over the RS-485/422
maximum distance of 4000’ (1220m). It is important to note
that the ISL333X don’t follow the RS-485 convention
whereby the inverting I/O is labeled “B/Z”, and the non
inverting I/O is “A/Y”. Thus, in the application diagrams
below the 333X A/Y (B/Z) pins connect to the B/Z (A/Y)
pins of the generic RS-485/RS-422 ICs.
RS-422 is typically a point-to-point (one driver talking to one
receiver on a bus), or a point-to-multipoint (multidrop)
standard that allows only one driver and up to 10 receivers
on each bus. Because of the one driver per bus limitation,
RS-422 networks use a two bus, full duplex structure for
bidirectional communication, and the Rx inputs and Tx
outputs (no tri-state required) connect to different busses, as
shown in Figure 10.
Conversely, RS-485 is a true multipoint standard, which
allows up to 32 devices (any combination of drivers- must be
tri-statable - and receivers) on each bus. Now bidirectional
communication takes place on a single bus, so the Rx inputs
and Tx outputs of a port connect to the same bus lines, as
shown in Figure 9. Each port set to RS-485 /422 mode
includes one Rx and one Tx.RS-232 is a point-to-point,
singled ended (signal voltages referenced to GND)
communication protocol targeting fairly short (<150’, 46m)
and low data rate (<1Mbps) applications. Each port contains
two transceivers (2 Tx and 2 Rx) in RS-232 mode. Protocol
selection is handled via a logic pin (SELX) for each port.
D
DI
A/Y
GND
0.1µF
R
T
GENERIC 1/2 DUPLEX 485 XCVR
+
A/Y
B/Z
GND
V
+5V
CC
R
D
May 27, 2008
FN6362.0
RO
RE
DE
DI