load guard inverse current reaction

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ElecCheng
Level 2
Level 2
10 sign-ins 5 questions asked 10 replies posted

Hi Expert,

I see in the website that you release a now product load guard, like BTG7050-2EPL. While reading the d/s, I find some confusion about inverse current protection. In page 26, we can see below two sentence. But it seems that they contradict to each other. From my understanding, this new feature is intended to protect the device while  inverse current, so the device will turn on. But I don't see clear description in d/s. So am I understanding right?

ElecCheng_0-1674099461659.png

Thank you for your help!

BR.

Elec Cheng

 

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Anshika_G
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First question asked 50 likes received 250 replies posted

Hi Cheng,

The inverse detection circuitry is designed to compare the Vbb and Vout and send the corresponding signal to microcontroller. Microcontroller could monitor the values of Vbb and Vout,which means it could detect that inverse mode condition is present. 

 The SENSE diagnostic output will have followed as diagnostic output in case of inverse mode condition when Input pin is low: 

G_Anshika_1-1675321205733.png

 G_Anshika_0-1675320125007.png
Hope this helps in clearing the confusion!

Best Regards,
Anshika

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Anshika_G
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First question asked 50 likes received 250 replies posted

Hello,

The statements are not contradictory but applies to device' status (ON/OFF). If you read further along the datasheet, in fig 22. InverseON - Channel behavior in case of applied inverse current, it clearly shows the channel behaviour.

From the statements that you have doubt upon : 

G_Anshika_0-1674123991677.png

1. During inverse current condition, the channel remains in ON or OFF state as long as |-IL| < |-IL(INV)|:  Refer to upper two images (CASE 1 and CASE2). It says that if the device is initially in ON or OFF state,it will remain in that state as long as IL<IL(INV).

2. The feature of InverseON allows to switch ON the channel during Inverse Current condition as long as

|-IL| < |IL(INV)| :  Refer to lower side imagesm (CASE3 and CASE 4). It means the INVERSEON features will allow us to switch the device even when the device is inverse current mode as long as IL<IL(INV). 

Please let me know if you have further doubts.

Best Regards,
Anshika


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Hi G,

All clear. Thanks for your detailed explanation.  But there is still one confusion. If inverse current happens while off, the inverse current flows through main FET's body diode. The body diode have limited current capability. The protection is the thermal protection. But from mu understanding, there is still a chance that the large current will break the MOSFET before hitting the thermal limit. One thing I can think about is, the device will turn on the main FET if inverse current happens while OFF. Also, we need to add inverse current detection circuit.

Do you have any comments for my thoughts? Just for friendly sharing!

BR,

Elec Cheng

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Anshika_G
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First question asked 50 likes received 250 replies posted

Hello,

If the switch is OFF when an inverse mode condition occurs, then the current will flow through the MOSFET’s intrinsic diode.
Also, as mentioned in the datasheet, device can be switched OFF to ON as long as the inverse load current does not exceed the maximum transient inverse load current.  The current flowing through the body diode will generate high power losses leading to an increase of overall device temperature. This may lead to a switch OFF of unaffected channels due to over-temperature.

Please note that inverse current condition is transient in nature that it only lasts for short duration. 

The product has already inbuilt an inverse detection circuitry (figure 21, page 27 of datasheet). 


G_Anshika_0-1675076068699.png

Hope it helps!

Best Regards,
Anshika

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Hi Anshika,

Thanks for your patient reply.

A further question for the inverse detection circuit, what is it used for since the device won't turn on automatically? Is is used for reverse battery issue where reverse current also occurs? Thanks.

BTW, as mentioned, the device is ISO 26262-ready. But what document on earth can you provide? May you send out one copy for reference? Thanks.

BR,

Elec Cheng

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Anshika_G
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First question asked 50 likes received 250 replies posted

Hello,

We offer the device to switch from OFF condition to ON condition as an additional feature in the device by " InverseON" functionality, which will help in reducing the losses(and to save the body diode and hence the device from being damaged ) as during off condition, inverse load current would be flowing through body diode, generating high losses (considering diode voltage drop) compared to ON condition when the current is flowing through the MOSFET channel.

For the document :
ISO-26262 ready is available for registered Infineon partners as mentioned on the product webpage. One can access the documents after the following steps : 

G_Anshika_0-1675254052976.png

Please have a look at file attached to get more details about Infineon functional saftey :  ISO-26262 

Best Regards,
Anshika

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Hi Anshika,

Thank you for your reply. 

About the " InverseON" functionality, I want to figure out, it's " the device can automatically switch from OFF condition to ON condition " or " the MCU can control the device switch from OFF condition to ON condition"? The main difference is whether we need external control in this function. Thanks.

BR,

CHENG

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Anshika_G
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First question asked 50 likes received 250 replies posted

Hi Cheng,

No, the device would not automatically switch from OFF to ON state. One need to send command to switch from OFF state to ON state from ECU's microcontroller. 

BR,
Anshika

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Hi Anshika,

Thanks for your reply. 

But this will lead to another question, what does the internal "inverse detection circuit" aim at? It seems we cannot use it for inverse current detection since there is no signal sent out. May you help clarify? Thank you very much!

ElecCheng_0-1675317319058.png

BR,

CHENG

 

 

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Anshika_G
Moderator
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First question asked 50 likes received 250 replies posted

Hi Cheng,

The inverse detection circuitry is designed to compare the Vbb and Vout and send the corresponding signal to microcontroller. Microcontroller could monitor the values of Vbb and Vout,which means it could detect that inverse mode condition is present. 

 The SENSE diagnostic output will have followed as diagnostic output in case of inverse mode condition when Input pin is low: 

G_Anshika_1-1675321205733.png

 G_Anshika_0-1675320125007.png
Hope this helps in clearing the confusion!

Best Regards,
Anshika

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Hi Anshika,

Understood. Thanks.

BR,

CHENG

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