V5 Brains out of stock

[technik3k]

I don’t know if RS485 driver chips have been updated recently from the original SN65HVD1782 part, that we found in the V5 brains back in 2018. Perhaps, @Art_Dutra_IV or @jpearman would have an answer.

That original driver chip has built-in protection from 16kV ESD pulses:

V5 brain ports break continually

I’ve taken some more internal pictures of the V5 brain and the RS-485 drivers are SN65HVD1782. SN65HVD178x datasheet says that it is rated up to 70v for transient voltage pulse and up to 16kV for ESD, but it says nothing about maximum current or power dissipation in the event of ESD. SM712 chip, that you have recommended, is rated at 19A current pulse and 600W power dissipation for ESD of up to 30kV. SM712 datasheet says that it has bi-directional asymmetric TVS diodes (+12/-7v) specifically d…

However, the power it could dissipate was, apparently, not enough for the charges that continuously spinning intakes of a typical VRC robots could produce and accumulate.

The datasheet for SN65HVD178x chip (pg. 20-21) recommends to use an external TVS array for higher energy (industrial) applications:

Although the SN65HVD178x family is internally protected against human-body-model ESD strikes up to 16 kV, additional protection against higher-energy transients can be provided at the application level by implementing external protection devices.

I don’t remember if we didn’t find any pin-compatible drivers at a time that offered better protection or they were too expensive, but the conclusion was that external TVS diodes like SM712/ SMBJ43CA offered good protection at a very reasonable price per channel.