MAX14781E_14 Datasheet, PDF (15/19 Pages) Maxim Integrated Products – Half-Duplex RS-485 Transceiver with Polarity Correction

MAX14781E
Half-Duplex RS-485 Transceiver
with Polarity Correction
Table 2. Polarity Detection Starting from Inverted Polarity
DE RE
INPUTS
(VB - V_A) FOR TIME > t_PM
Open/Shorted
POLARITY DETECTION
ON
0
0
> -50mV
ON
< -200mV
ON
1
1
X
OFF
1
0
X
OFF
0
1
X
OFF
X = Don’t care
POLARITY AFTER t_PM TIME
Inverted/ Previous Detection Polarity
Inverted/ Previous Detection Polarity
Normal
Previous Detection Polarity
Previous Detection Polarity
Previous Detection Polarity
The polarity detection circuitry is disabled when the
driver is enabled or when the transceiver is in low-power
shutdown mode.
±25kV ESD (HBM) Protection
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 MAX14781E have extra protection
against static electricity. Maxim’s engineers have
developed state-of-the-art structures to protect these
pins against ESD of ±25kV (HBM) without damage. The
ESD structures withstand high ESD in all states: normal
operation, shutdown, and powered down. After an ESD
event, the MAX14781E keeps working without latch-up
or damage.
The transmitter output and receiver input of the
MAX14781E are characterized for protection to the
following limits:
●● ±25kV using the Human Body Model
●● ±9kV 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.
RC
1MΩ
RD
1500Ω
CHARGE-CURRENT-
LIMIT RESISTOR
DISCHARGE
RESISTANCE
HIGH-
VOLTAGE
DC
SOURCE
Cs
100pF
STORAGE
CAPACITOR
DEVICE
UNDER
TEST
Figure 10a. Human Body ESD Test Model
www.maximintegrated.com
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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