CAN Safety Mechanism with TLF35584

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Mcoban
Level 2
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Hello there,

 As you can see picture below, for safety purpose it suggested two different path options. 

For the first option, you suggested to use mosfet triggering but can we do cut off the VCC Supply Voltage via SPI Communication? What is the main purpose to not using SPI to cut off the supply voltage instead of using TLF SS pins?

 

Regards,

Mehmet

MicrosoftTeams-image (16).png

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1 Solution
Albab_A
Moderator
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5 likes given 50 solutions authored 100 replies posted

Hello,

As you can check in the below diagram when you try to disable the QCO the following changes will occur if you are thinking from the safety point of view-

Albab_A_0-1704887519222.png

1. When you try to disable the QCO then the associated post regulators which are following QCO under power sequencing as shown below will get off.

Albab_A_1-1704887702984.png

2. In case of false triggering you are turning Off the QCO as well.

Therefore in order to not compromise with the stability and the safety critical system we have incorporated the proposed design.

 

Best Regards,

Albab

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Albab_A
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Hello,

From what I have understood from your query , you cannot disable the Vcc pin in the CAN TLE9252V by SPI  as it is not equipped with this  feature.

Best Regards,

Albab

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Mcoban
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Hello Albab,

Thanks a lot for your response. 

You can disable the VCC inside of TLF35584 PMIC. TLF produce the VCC in itself. If you give SPI Signal to cutoff the  Power, you can disable. I understood with this way. Please correct me if I am wrong.

Please look at the attached.

Regards,

Mehmet

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Translation_Bot
Community Manager
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Xuel11_0-1704698784114.png

Because in most cases, the SS state is not equal to VCC, the SS safety shutdown path is a safety mechanism for the power supply and has a higher functional safety level, and SPI can only control VCC through the TLF35584 state machine migration and cannot directly control Vcc.

smartconx_target@Q!w2e3r4t5y6u7i8o9p0||/t5/AURIX/%E9%87%87%E7%94%A8-TLF35584-%E7%9A%84-CAN-%E5%AE%89%E5%85%A8%E6%9C%BA%E5%88%B6/m-p/672172

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Mcoban
Level 2
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Hi Xuel11,

Thanks a lot for your answer but we are using LDO_Com to supply to CAN IC. Are your statements also valid for LDO_Com?

 

Mcoban_0-1704710321229.png

 

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Translation_Bot
Community Manager
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As shown in the figure, in the 'INIT' stage, LD_com is not equal to SSC, and in the 'WAKE', 'SLEEP' and 'NORMAL' state, LD_COM's state can be controlled by SPI. For details, refer to section 11 of the 35584 chip data sheet

smartconx_target@Q!w2e3r4t5y6u7i8o9p0||/t5/AURIX/%E9%87%87%E7%94%A8-TLF35584-%E7%9A%84-CAN-%E5%AE%89%E5%85%A8%E6%9C%BA%E5%88%B6/m-p/672416

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in INIT state, it says "* : Switched ON by entering the INIT state, then selectable via SPI". Therefore, it means that no need to use SS1/2 pin to CAN's EN pin. VCC Supply can be controllable via SPI.

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Translation_Bot
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1704716541684.png

 The migration of the state machine is not entirely active. The conditions in the picture frame will cause the chip to passively enter the init state, which will cause LD_COM to re-supply power, which does not meet safety requirements

smartconx_target@Q!w2e3r4t5y6u7i8o9p0||/t5/AURIX/%E9%87%87%E7%94%A8-TLF35584-%E7%9A%84-CAN-%E5%AE%89%E5%85%A8%E6%9C%BA%E5%88%B6/m-p/672466

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Albab_A
Moderator
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Moderator
5 likes given 50 solutions authored 100 replies posted

Hello,

As you can check in the below diagram when you try to disable the QCO the following changes will occur if you are thinking from the safety point of view-

Albab_A_0-1704887519222.png

1. When you try to disable the QCO then the associated post regulators which are following QCO under power sequencing as shown below will get off.

Albab_A_1-1704887702984.png

2. In case of false triggering you are turning Off the QCO as well.

Therefore in order to not compromise with the stability and the safety critical system we have incorporated the proposed design.

 

Best Regards,

Albab

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