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Part Number: SN65HVD1785
I m trying to design a robust circuit using SN65HVD1785
circuit power supply 12-48 V DC
during a test using 40V DC power supply, I deliberately mis-wired BUS A (PIN6) to V+ (40V ) , but the IC failed ,
I did the the same test several times with new ICs but result was the same, IC fails
I need my circuit never be failed at mis-wiring situation, do I missed anything in my design?
In reply to Max Robertson:
In reply to Macit Seyedin:
my circuit almost finished.
as I mentioned before, there are 2 TVS diodes (SMAJ48CA) 1 : between bus A and GND , 2: bus B and GND
I made 10 sample devices, all 10 devices are common connected to data bus, and did some robustness forced tests as below:
1) mis-wire connetion:
all devices survive from all possible combination of mis-wiring 55V, about hundred iterations.
the result is as I expected, and pass the test
2) ESD test
I did the test with ESD gun 20 pulse +6000V and 20 pulse -6000V to both A and B of bus respect to GND
but some devices' ICs (sn65HVD1786) fail after ESD test,
I did the experiment several times and in some tests 1 IC , some times 2ICs or 3 ICs fail both A and B some times only A or B
fail mostly occures in devices near the test point, all TVS diodes survive after ESD
I also repeated my test using different IC sn65HVD1781, but the result is same:
they fail after ESD shock,
I have no idea why this happen, according datasheet both sn65HVD181 and sn65HVD1786 are ESD protected up to +-16000 volts, but they fail in my 6000V test
my previous tests were IEC-04 (8kv) direct discharge from 7 mm , I saw the arc from tip of gun to data line
I also did new test with IEC-01 (2kv) from 1mm - arc rarely can be seen - after 50 shots, B line damaged again, first nearest node of 10 nodes,
are there other pin compatible alternatives like sn65HVD1781 / sn65HVD1786 ?
changing PCB design is difficult, maybe my last choice !
thank you very much for spend time and caring about my project
my test setup is 10 circuits connected (soldered) each other using 10 cm 0,34mm2 cables V+, V-, D+, D-
there is a 15cm male 4x0,34mm2 socket soldered to first circuit as input
I connect another 15 cm female socket to input, other side of female soket is 4x0,34mm2 free cables (V+)(V-)(D+)(D-)
gun GND is connected to (V-)
I strike (V+)(D+)(D-)
no problem on (V+) side , there is TVS diode and TPS54360, solved in other thread recommended by John Tucker
so A, B are striked through 15 cm female + 15 cm male soket
TVS diodes are on circuit very close to A, B of IC,
I should say TVS diodes in my current PCB are soldered manually , they were carefully soldered and checked before test
but maybe considered as fail cause
my new PCB will arrive soon,
let me redo my test again with new revision PCB to acheive more precise facts to solve the problem
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