MAX14948 Datasheet, PDF (17/21 Pages) Maxim Integrated Products – 5kVRMS Isolated 500kbps Half-Duplex RS-485

MAX14948
5kV_RMS Isolated 500kbps Half-Duplex RS-485/
RS-422 Transceiver with ±30kV ESD Protection
Ensure that the decoupling capacitors between V_DDA and
GNDA and between V_LDO, V_DDB, and GNDB are located
as close as possible to the IC to minimize inductance.
Route important signal lines close to the ground plane
to minimize possible external influences. On the cable
side of the device, it is good practice to have the bus
connectors and termination resistor as close as possible
to the A and B pins.
Extended ESD Protection
ESD-protection structures are incorporated on all pins
to protect against electrostatic discharge encountered
during handling and assembly. The driver outputs and
receiver inputs of the MAX14948 have extra protection
against static electricity. The ESD structures withstand
high ESD in normal operation and when powered down.
After an ESD event, the devices keep working without
latchup or damage.
Bypass V_DDA to GNDA and bypass V_DDB and VLDO
to GNDB with 0.1μF and 1μF capacitors to ensure
maximum ESD protection.
ESD protection can be tested in various ways. The transmitter
outputs and receiver inputs of the device are characterized for
protection to the cable-side ground (GNDB) to the following
limits:
●● ±30kV HBM
●● ±15kV using the Air-Gap Discharge method specified
in IEC 61000-4-2
●● ±10kV using the Contact Discharge method speci-
fied in the IEC 61000-4-2
ESD Test Conditions
ESD performance depends on a variety of conditions.
Contact Maxim for a reliability report that documents test
setup, test methodology, and test results.
Human Body Model (HBM)
Figure 10 shows the HBM test model and Figure 11
shows the current waveform it generates when dis-
charged in a low-impedance state. This model consists of
a 100pF capacitor charged to the ESD voltage of interest,
which is then discharged in to the test device through a
1.5kΩ resistor.
IEC 61000-4-2
The IEC 61000-4-2 standard covers ESD testing and
performance of finished equipment. However, it does not
specifically refer to integrated circuits. The device helps in
designing equipment to meet IEC 61000-4-2 without the
need for additional ESD-protection components.
The major difference between tests done using the HBM
and IEC 61000-4-2 is higher peak current in IEC 61000-
4-2 because series resistance is lower in the IEC 61000-
4-2 model. Hence, the ESD withstand voltage measured
to IEC 61000-4-2 is generally lower than that measured
using the HBM.
Figure 12 shows the IEC 61000-4-2 model and
Figure 13 shows the current waveform for IEC 61000-4-2
ESD Contact Discharge Test.
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