AlexanderTheGreat
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Hello,
during initial operation testing in the lab I discovered a (in my opinion) strange power-on effect. First I will describe the circuit and the behaviour of the circuit:
I use a NXP Highspeed CAN Transceiver (TJA1041A) with CAN wake up functionality. The transceiver is supplied with the battery voltage, when it sees bus communication the transceiver will switch the battery voltage through the inhibit output to the voltage regulator, and thereby activates the regulator. I'm testing the circuit without any software and CAN bus. According to the datasheet the transceiver enters a power-on state when it sees a battery voltage for the first time. In this power-on state, the battery voltage is switched to the inhibit output. So, it's possible to activate the circuit without CAN wake up.
One problem are the input capacitors: you can only reactivate the circuit (enter the power-on state) after the capacitors are discharged. So that the transceiver again sees the voltage the "first time"...
Well, that worked very well but after a around 20 cycles it wasn't possible to activate the transceiver again. I checked the voltage on the input capacitors but they were discharged completely. Also a second PCB showed the same behaviour after around 20 cycles. Well, when I bypassed the battery voltage to the enable input, the transceiver entered the on-state and activated the power supply, so it was possible to resume testing the circuit.
Now my question: I checked the datasheet and everything else with the circuit, but I still don't understand the behaviour. For example: I thought that there is maybe some kind of non volatile counter which deactivates the power-on state after a few cycles. But there was nothing noted about something like that in the datasheet. Well, as I said, it was possible to go on with the testing but it would be nice to understand that behaviour.
Did anyone discovered a similar behaviour or knows why the transceiver behaves like this?
during initial operation testing in the lab I discovered a (in my opinion) strange power-on effect. First I will describe the circuit and the behaviour of the circuit:
I use a NXP Highspeed CAN Transceiver (TJA1041A) with CAN wake up functionality. The transceiver is supplied with the battery voltage, when it sees bus communication the transceiver will switch the battery voltage through the inhibit output to the voltage regulator, and thereby activates the regulator. I'm testing the circuit without any software and CAN bus. According to the datasheet the transceiver enters a power-on state when it sees a battery voltage for the first time. In this power-on state, the battery voltage is switched to the inhibit output. So, it's possible to activate the circuit without CAN wake up.
One problem are the input capacitors: you can only reactivate the circuit (enter the power-on state) after the capacitors are discharged. So that the transceiver again sees the voltage the "first time"...
Well, that worked very well but after a around 20 cycles it wasn't possible to activate the transceiver again. I checked the voltage on the input capacitors but they were discharged completely. Also a second PCB showed the same behaviour after around 20 cycles. Well, when I bypassed the battery voltage to the enable input, the transceiver entered the on-state and activated the power supply, so it was possible to resume testing the circuit.
Now my question: I checked the datasheet and everything else with the circuit, but I still don't understand the behaviour. For example: I thought that there is maybe some kind of non volatile counter which deactivates the power-on state after a few cycles. But there was nothing noted about something like that in the datasheet. Well, as I said, it was possible to go on with the testing but it would be nice to understand that behaviour.
Did anyone discovered a similar behaviour or knows why the transceiver behaves like this?