Hi Team,
Can you help with this customer inquiry?
Will SN65C1168E-SEP be damaged if either an unpowered driver or receiver is driven from an externally powered device (say another driver/receiver on the bus)?
Section 6.5 of the datasheet seems to imply that the driver can be driven while powered off.
Thanks in advance.
Regards,
Marvin
Hi Marvin,
It depends on what pins are going to be subject to the power during power off conditions.
Pin ratings are shown in Abs max table:
Based on the pin ratings a few things can be determined:
1. A/B have a max rating of +/-14V (recommended is +/-7V however) and there is no mention of VCC in the spec so it is rated to that voltage regardless of VCC.
2. Enables and Driver (D) pins are rated from -0.5V to 7V - this indicates there is a diode from ground to the input - but there is no dependence on VCC so a positive signal <7V shouldn't be too harmful (rec. is to keep it within VCC range - but in case of power on line before it shouldn't be that large of concern if the power is within rating - but larger leakage currents are possible)
3. The receiver outputs are dependent on VCC as the max is VCC + 0.5V so this pin isn't rated for really any signal on it before VCC - however this is purely an output so unless there is a pull-up to a different source it shouldn't be an issue.
The eq. circuits listed in the datasheet (shown below) Confirm these ratings.
The silicon is rated to hit these voltages and really the only risk of back-powering to VCC is on the "R" pin - but there could be more leakage current (we only rated it on the output pins for this device - but leakage current could be increased across the board on any pin that receives voltage before VCC - with the exception of 'R')
Please let me know if you have any other questions.
Best,
Parker Dodson
