What is Vehicle Battery Voltage when shutdown completes ?

Started by learn 6 years ago2 replieslatest reply 6 years ago106 views

A typical Powertrain Electronic Control Unit (ECU) is wired with Infineon Aurix Tricore TC29x Microcontroller.  Embedded Software running in the ECU is in C language.

Application software running in this ECU calls the lower layer software interface function to shutdown the ECU.  This transitions CAN Transceiver to sleep mode.  CAN Transceiver has INH (Inhibit) Output for switching external voltage regulators.  The CAN Transceiver datasheet says "Entire node can be powered down via this INH output.

In a typical system, what will be measured value of battery voltage when shutdown is complete ?

Also, there are Vcc voltage and other related voltages in our ECU that power microcontroller, CAN Transceivers, LIN Transceivers, Voltage Regulator ICs and other ICs. 

What will be measured Vcc and other related voltages when shutdown is complete ?

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Reply by sbkennFebruary 17, 2017

A full charged 12V battery will hold 12.6V, likely dropping back to probably 12.4 over a couple of hours.

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Reply by 5igna1February 22, 2017
> What will be measured Vcc and other related voltages when shutdown is complete ?

We can only guess on how "your" ECU is designed. 

Typically INH pin on transceiver is useful for simple nodes, that can just turn off completely at reception of the very last "master sleep" packet.

Short answer - after shutdown is completed a Vcc will be zero. Transceiver itself operates only partially taking supply directly from battery's 12V, while 5V voltage regulator that supplies this transceiver is in OFF state. Then at first activity on bus a transceiver through the same INH pin activates the whole node activating voltage regulator.

Note: controller in this arrangement can not wake up itself (periodically or checking it's inputs). Obviously this strategy is well suited for essentially "slave" nodes. I doubt that it is applicable for such a "master" an ECU is, that has to have more advanced power arrangement.