Hello support team,
I have some questions about the isolated RS-485 transceiver ISO1410.
Our customer is considering adopting ISO1410 currently, .
When noise is applied in the electrical fast transient / burst immunity test (IEC61000-4-4), the communication error occurs in RS-485 communication.
The test conditions are as follows.
・ electrical fast transient / burst immunity test (IEC61000-4-4)
・ Mode: Common mode
・ Voltage: -4 kV
・ Frequency: 5 kHz and 100 kHz
・ GND1 is connected to the power line, GND2 is used close to the communication line (FG)
The specifications of RS-485 communication are as follows.
・ Data rate: 38400bps
・ Type: Half-duplex
Immediately after applying noise in the electrical fast transient / burst immunity test, the receiver output R of ISO1410 is forced high level for about 100 μs regardless of the state of the differential bus signal.
[Question]
1. The customer guesses that the cause of the above phenomenon is a malfunction of the “Glitch-Free Power up Power Down function”.
Is his opinion correct?
2. If the answer to question 1 is "Yes",
2-1. Which does "Glitch-Free Power up Power Down" function work on the circuit, Vcc1 side or Vcc2 side?
2-2. How does the internal circuit behave when "Glitch-Free Power up Power Down" is malfunctioning?
2-3. Is there a recommended circuit to prevent the mulfanction of "Glitch-Free Power up Power Down"?
3. If the answer to question 1 is "No",
3-1. What are the possible malfunction factors?
4. As a noise countermeasure, the customer is considering putting about 1000pF of a ceramic capacitor between the differential signals lines (A and B). Does adding a capacitor interfere with the operation of this IC?
Sincerely,
M. Tachibana