MAX14780E Datasheet, PDF (11/14 Pages) Maxim Integrated Products – 5.0V, 30kV ESD-Protected, Fail-Safe, Hot-Swap, RS-485/RS-422 Transceiver

+5.0V, ±30kV ESD-Protected, Fail-Safe,
Hot-Swap, RS-485/RS-422 Transceiver
CMOS input. Whenever VCC drops below 1V, the hot-
swap input is reset.
For RE there is a complementary circuit employing two
pMOS devices pulling RE to VCC.
±30kV ESD Protection
As with all Maxim devices, ESD-protection structures are
incorporated on all pins to protect against electrostatic
discharges encountered during handling and assembly.
The driver output and receiver input of the MAX14780E
have extra protection against static electricity. Maxim’s
engineers have developed state-of-the-art structures to
protect these pins against ESD of ±30kV without dam-
age. The ESD structures withstand high ESD in all states:
normal operation, shutdown, and powered down. After
an ESD event, the MAX14780E keeps working without
latchup or damage.
ESD protection can be tested in various ways. The trans-
mitter output and receiver input of the MAX14780E are
characterized for protection to the following limits:
• ±30kV using the Human Body Model
• ±12kV using the Contact Discharge method specified
in IEC 61000-4-2
• ±15kV using the Air-Gap Discharge method specified
in 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
Figure 10a shows the Human Body Model, and Figure 10b
shows the current waveform it generates when dis-
charged into a low impedance. This model consists of a
100pF capacitor charged to the ESD voltage of interest,
which is then discharged into 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 MAX14780E
helps you design equipment to meet IEC 61000-4-2, with-
out the need for additional ESD-protection components.
The major difference between tests done using the
Human Body Model 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 gen-
erally lower than that measured using the Human
Body Model. Figure 10c shows the IEC 61000-4-2
model, and Figure 10d shows the current waveform for
IEC 61000‑4‑2 ESD Contact Discharge test.
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. Of course, all pins require this protection, not
just RS-485 inputs and outputs.
R_C
1MΩ
R_D
1500Ω
CHARGE-CURRENT-
LIMIT RESISTOR
DISCHARGE
RESISTANCE
HIGH-
VOLTAGE
DC
SOURCE
Cs
100pF
STORAGE
CAPACITOR
Figure 10a. Human Body ESD Test Model
DEVICE
UNDER
TEST
IP 100%
90%
AMPS
36.8%
10%
0
0 _tRL
Ir
PEAK-TO-PEAK RINGING
(NOT DRAWN TO SCALE)
TIME
t_DL
CURRENT WAVEFORM
Figure 10b. Human Body Current Waveform
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