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EIA RS-485 specifies a ±7V ground difference between devices on the bus. This permits the bus voltage to range from

+12V (5V + 7V) to -7V (0 - 7V). The ASM712 is designed to protect two RS-485 data lines in extended common mode

applications. The ASM712 may be used to protect devices from transient voltages resulting from ESD, EFT, and light

ning. The device is designed with asymmetrical operating voltages for optimum protection. The TVS diodes at pins 1 and

2 have a working voltage of 12volts. These pins are connected to the differential data line pairs. The TVS diodes at pin 3

have a working voltage of 7volts. Pin 3 is connected to ground. The internal TVS diodes of the ASM712 will protect the

transceiver input from positive transient voltage spikes greater than 12V and negative spikes greater than 7V.

ASM712

ASM05

ASM712 on RS-485 Data Lines Application

ASM712