ISL41387IRZ Intersil, ISL41387IRZ Datasheet - Page 14

• Manufacturer Part Number: ISL41387IRZ
• Description: IC TXRX DUAL PROTOCAL ESD 40-QFN
• Manufacturer: Intersil
• Type: Transceiverr

Specifications of ISL41387IRZ

• Number Of Drivers/receivers: 2/2
• Protocol: RS422, RS485
• Voltage - Supply: 4.5 V ~ 5.5 V
• Mounting Type: Surface Mount
• Package / Case: 40-VFQFN, 40-VFQFPN
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

ISL81387, ISL41387 Advantages
These dual protocol ICs offer many parametric
improvements versus those offered on competing dual
protocol devices. Some of the major improvements are:
• 15kV Bus Pin ESD - Eases board level requirements
• 2.7V Diff V
• Full Failsafe RS-485 Rx - Eliminates bus biasing
• Selectable RS-485 Data Rate - Up to 20Mbps, or slewrate
• High RS-232 Data Rate - >460kbps
• Lower Tx and Rx Skews - Wider, consistent bit widths
• Lower I
• Flow-Thru Pinouts - Tx, Rx bus pins on one side/logic pins
• Smaller (SSOP and QFN) and Pb-free packaging
RS-232 Mode
RX FEATURES
RS-232 receivers invert and convert RS-232 input levels
(±3V to ±25V) to the standard TTL/CMOS levels required by
a UART, ASIC, or µcontroller serial port. Receivers are
designed to operate at faster data rates than the drivers, and
they feature very low skews (10ns) so the receivers
contribute negligibly to bit width distortion. Inputs include the
standard required 3kΩ to 7kΩ pull-down resistor, so unused
inputs may be left unconnected. Rx inputs also have built-in
hysteresis to increase noise immunity, and to decrease
erroneous triggering due to slowly transitioning input signals.
Rx outputs are short circuit protected, and are tri-statable via
the active high RXEN pin, when the IC is shutdown (SHDN;
see Tables 2 and 3, and “Low Power Shutdown (SHDN)
Mode” on page 16), or via the active low RXEN pin available
on the QFN package option (see“ISL41387 (QFN Package)
Special Features” on page 17 for more details).
TX FEATURES
RS-232 drivers invert and convert the standard TTL/CMOS
levels from a UART, or µcontroller serial port to RS-232
compliant levels (±5V minimum). The Tx delivers these
compliant output levels even at data rates of 650kbps, and
with loads of 1000pF. The drivers are designed for low skew
(typically 12% of the 500kbps bit width), and are compliant to
the RS-232 slew rate spec (4V/µs to 30V/µs) for a wide
range of load capacitances. Tx inputs float if left
unconnected, and may cause I
results, connect unused inputs to GND.
Tx outputs are short circuit protected, and incorporate a
thermal SHDN feature to protect the IC in situations of
severe power dissipation. See the RS-485 section for more
details. Drivers tri-state via the active high DEN pin, in SHDN
limited for low EMI and fewer termination issues
on the other, for easy routing to connector/UART
CC
OUT
- Max I
- Better Noise immunity and/or distance
CC
is 2x to 4x lower than competition
14
CC
increases. For the best
ISL81387, ISL41387
(see Tables 2 and 3, and “Low Power Shutdown (SHDN)
Mode” on page 16), or when the 5V power supply is off.
CHARGE PUMPS
The on-chip charge pumps create the RS-232 transmitter
power supplies (typically +6/-7V) from a single supply as low
as 4.5V, and are enabled only if the port is configured for
RS-232 operation, and not in SHDN. The efficient design
requires only four small 0.1µF capacitors for the voltage
doubler and inverter functions. By operating discontinuously
(i.e., turning off as soon as V+ and V- pump up to the
nominal values), the charge pump contribution to RS-232
mode I
that require the charge pump in RS-485 mode, disabling the
charge pump saves power, and minimizes noise. If the
application is a dedicated RS-485 port, then the charge
pump capacitors aren’t even required.
DATA RATES AND CABLING
Drivers operate at data rates up to 650kbps, and are
guaranteed for data rates up to 460kbps. The charge pumps
and drivers are designed such that one driver can be
operated at the rated load, and at 460kbps (see Figure 33).
Figure 33 also shows that drivers can easily drive several
thousands of picofarads at data rates up to 250kbps, while
still delivering compliant ±5V output levels.
Receivers operate at data rates up to 2Mbps. They are
designed for a higher data rate to facilitate faster factory
downloading of software into the final product, thereby
improving the user’s manufacturing throughput.
Figures 36 and 37 illustrate driver and receiver waveforms at
250kbps, and 500kbps, respectively. For these graphs, one
driver drives the specified capacitive load, and a receiver.
RS-232 doesn’t require anything special for cabling; just a
single bus wire per transmitter and receiver, and another
wire for GND. So an ISL81387, ISL41387 RS-232 port uses
a five conductor cable for interconnection. Bus terminations
are not required, nor allowed, by the RS-232 standard.
RS-485 Mode
RX FEATURES
RS-485 receivers convert differential input signals as small
as 200mV, as required by the RS-485 and RS-422
standards, to TTL/CMOS output levels. The differential Rx
provides maximum sensitivity, noise immunity, and common
mode rejection. Per the RS-485 standard, receiver inputs
function with common mode voltages as great as ±7V
outside the power supplies (i.e., +12V and -7V), making
them ideal for long networks where induced voltages are a
realistic concern. Each RS-485, RS-422 port includes a
single receiver (RA), and the unused Rx output (RB) is
disabled.
CC
is reduced significantly. Unlike competing devices
November 21, 2007
FN6201.3