SP3080E Datasheet, PDF (18/21 Pages) Sipex Corporation – Advanced-Failsafe RS-485/RS-422 Transceiver 1/8th Unit Load, Slew-Limited, ±15kV ESD-Protected

ESD TEST CONDITIONS
ESD performance depends on a variety of con-
ditions. Contact Sipex for a reliability report
that documents test setup, methodology and
results.
IEC 1000-4-2
The IEC 1000-4-2 standard covers ESD testing
and performance of finished equipment. How-
ever, it does not specifically refer to integrated
circuits. The SP3080E helps you design equip-
ment to meet IEC 1000-4-2, without sacrificing
board space and cost for external ESD-protec-
tion components.
The major difference between tests done us-
ing the Human Body Model and IEC 1000-4-2
is a higher peak current in IEC 1000-4-2 series
resistance is lower in the IEC 1000-4-2 model.
Hence, the ESD withstand voltage measured to
IEC 1000-4-2 is generally lower than that mea-
sured using the human body model.
The air-gap test involves approaching the
device with a charged probe. The contact dis-
charge method connects the probe to the de-
vice before the probe is energized.
DESCRIPTION
50ns. If the inputs are in this state for at least
600ns, the parts are shutdown.
Enable times tZH and tZL apply when the part is
not in low-power shutdown state. Enable times
tZH(SHDN) and tZL(SHDN) apply when the parts
are shut down. The drivers and receivers take
longer to become enabled from low power shut-
down mode tZL(SHDN) and tZL(SHDN) than from
driver/receiver-disable mode (tZH, tZL).
DRIVER OUTPUT PROTECTION
Two mechanisms prevent excessive output cur-
rent and power dissipation caused by faults or
by bus contention. First, a driver-current limit
on the output stage provides immediate protec-
tion against short circuits over the whole com-
mon-mode voltage range. Second, a thermal-
shutdown circuit forces the driver outputs into
a high-impedance state if junction temperature
becomes excessive.
LINE LENGTH, EMI, AND REFLECTIONS
SP3080E feature controlled slew-rate driv-
ers that minimize EMI and reduce reflections
caused by improperly terminated cables.
MACHINE MODEL
The machine model for ESD tests all pins using
a 200pF storage capacitor and zero discharge
resistance. The objective is to emulate the
stress caused when I/O pins are contacted by
handling equipment during test and assembly.
256 TRANSCEIVERS ON THE BUS
The standard RS-485 receiver input impedance
is 12kΩ (1 unit load). A standard driver can
drive up to 32 unit loads. The SP3080E fam-
ily of transceivers has only a 1/8th unit load re-
ceiver input impedance (96kΩ), thereby allow-
ing eight times as many, up to 256, transceivers
to be connected in parallel on a communication
line. Any combination of these devices and oth-
er RS-485 transceivers up to a total of 32 unit
loads may be connected to the line.
LOW POWER SHUTDOWN MODE
Low-power shutdown mode is initiated by bring-
ing both RE high and DE low simultaneously.
While in shutdown devices typically draw only
200nA of supply current. DE and RE may be
tied together and driven by a single control sig-
nal. Devices are guaranteed not to enter shut-
down if RE is high and DE is low for less than
SP3080E driver rise and fall times are limited
to no faster than 667ns, allowing error-free data
transmission up to 115kbps.
The RS-485/RS-422 standard covers line
lengths up to 4,000ft. Maximum achievable line
length is a function of signal attenuation and
noise. Use of slew-controlled drivers such as
the SP3080E may help to reduce crosstalk in-
terference and permit communication over lon-
ger transmission lines.
Termination prevents reflections by eliminating
the impedance mismatches on a transmission
line. Line termination is typically used if rise
and fall times are shorter than the round-trip
signal propagation time. Slew-limited drivers
may reduce or eliminate the need for cable ter-
mination in many applications.
Rev N 9/15/2006
SP3080E Advanced RS485 Transceivers
18
© Copyright 2006 Sipex Corporation