ISL3330_14 Datasheet, PDF (18/25 Pages) Intersil Corporation – 3.3V, ±15kV ESD Protected, Dual Protocol (RS-232/RS-485) Transceivers

ISL3330, ISL3331
slew limited edges permit longer unterminated networks, or
longer stubs off terminated busses, and help minimize EMI
and reflections. Nevertheless, for the best jitter performance
when driving long cables, the faster speed options may be
preferable, even at lower data rates. The faster output
transitions deliver less variability (jitter) when loaded with the
large capacitance associated with long cables. Of course,
faster transitions require more attention to ensuring short
stub lengths and quality terminations, so there are trade-offs
to be made. Assuming a jitter budget of 10%, it is preferable
to go with the slow speed option for data rates of 115kbps or
less to minimize fast edge effects. Likewise, the medium
speed option is a good choice for data rates between
115kbps and 460kbps. For higher data rates, or when the
absolute best jitter is required, use the high speed option.
Tx/Rx
1kΩ
OR NC
ISL3331 +3.3V
RXEN *
RA
RXEN
V_CC
RB
A
+
0.1µF
DEN
DY
D
Y
Z
GND
ACTIVE HIGH RX ENABLE
ISL3331 ^+3.3V
RXEN
RA
RXEN *
Tx/Rx
DEN
DY
V_CC
RB
A
Y
D
Z
GND
* QFN ONLY
+
0.1µF
ACTIVE LOW RX ENABLE
FIGURE 12. USING ACTIVE LOW vs ACTIVE HIGH RX
ENABLE
Evaluation Board
An evaluation board, part number ISL3331EVAL1Z, is
available to assist in assessing the dual protocol IC’s
performance. The evaluation board contains a QFN
packaged device, but because the same die is used in all
packages, the board is also useful for evaluating the
functionality of the other versions. The board’s design allows
for evaluation of all standard features, plus the QFN specific
features. Refer to the evaluation board application note for
details, and contact your sales representative for ordering
information.
18
FN6361.0
May 20, 2008