Ground surge destroys SN65HVD251

Hi Dmitry,

Do you have any more information on the magnitude of this noise? And with respect to which pins?

If the local ground is bouncing above the local VCC I could see this causing damage to the device since it is only rated for up to -0.3 volts from VCC to GND. But if the ground of the entire module’s ground is bouncing then the standoff voltage of the bus pin with respect to local ground would come into play. This is much more resilient to noise, since the device can handle ±36 volts on CANH and CANL with respect to local ground with no time limit.  

If you could share any more information about the failure that you are seeing, a schematic, a possible some screen shots from an oscilloscope that would really help.  

Thanks,

John

John, thank you for the suggestion. Attached pls see the schematic, DDx are the CAN trancievers8688.P-CAD EDA - [Analog_Scan_&_VFD].pdf

Alternatively, the following schematic is much more tolerant to the ground noise and the customer could not see damage in the lab: 2703.P-CAD EDA - [Analog_Scan_&_VFD]2.pdf

Pls check and advise.

Hi Dmitry,

Can you share the values of the bus capacitors and common mode choke? These could be providing passive filtering of high frequency noise, that helps dampen what reaches the transceiver. It still suprises me that you say the transcevier is being damaged. Do

Can you describe what is being damaged on the device? Is the bus no longer being driven? For example, is the driver is being damaged?

Also, are XPA and XP8 off board connectors? And is R126 a termination resistor? I usually see two connections to bus connectors, not three.

Thanks,

John

Hi,

for the 1st schematic the values are:

VD6,7 SMBJ36CA

R4, R5 - 1 Ohm.
R*8 - 47 kOhm
R126 - 120 Ohm (termination)
R108 - 1 Ohm
C51 - 0,1 uF
C62, C63 - 0,1 uF.

For the 2d schematic:

Filter is B82790S0513N201 and the input capacitors are 1 nF