Hello,
I'm wondering how to estimate the power dissipation of TCAN1042-Q1 when its CAN bus outputs are short-circuited to GND. Could you review my idea?
- Supply current consumed by internal circuit (ICC(INT)): The data sheet provides the Max ICC (5-V supply current) value in dominant state with bus fault as 180 mA. I guess it contains IOS(SS_DOM) (short-circuit steady-state output current, dominant, Normal mode) of 100 mA which will be drawn from VCC supply pin. The supply current consumed by the device internal circuit in this fault state can be estimated as 80 mA by subtracting 100 mA from 180 mA.
- Supply current consumed by short-circuit output current (ICC(OUT)): The short-circuit current flowing out from CANH pin will be drawn from VCC supply pin. The average short-circuit current IOS(AVG) can be estimated by the equation (1) on page 17 of the data sheet.
- Power dissipation: The power dissipation of this device in this fault state can eventually be calculated as PD(SS) = VCC × (ICC(INT) + ICC(OUT)).
If the junction temperature raised by this heat dissipation exceeds the thermal shutdown threshold TTSD, will it turn off the device?
Additional Question
- Is there any way for a system (MCU, etc.) to know whether a TCAN1042-Q1 is in a bus fault condition caused by bus short circuit?
Best regards,
Shinichi Yokota