Can I connect the STATUS outputs of three BTS3011TE Smart low-side power switches to 1 pullup resistor and one MCU input?

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Woody
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The title says it all. I recon that I can parallelize the STATUS outputs of these devices, but I would like to make sure before using this in a design.

Kind regards,

Paul

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Xiangrui
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Hi,

you can use it in this way in principle.

However, it means that these three switches will be turned OFF whenever failure occurs by one of three switches. 

If you want to achieve this function, then there is no problem from electrical side.

BR,

Xiangrui

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Xiangrui
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Hi,

you can use it in this way in principle.

However, it means that these three switches will be turned OFF whenever failure occurs by one of three switches. 

If you want to achieve this function, then there is no problem from electrical side.

BR,

Xiangrui

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Woody
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Hi Xiangrui,

Thanks for your swift answer!

These switches control three valves on one device and should all be turned off if one of them overheats. that was the reason for my initial question about the paralleling.

However, your answer made me question my understanding of the working of the status pin. What I learn from your explanation is that a BTS3011 turns off if its status pin is set to low.

What I learn from the DS:  A thermal fault pulls the status pin low. The status pin stays low until it is reset. Resetting is done by actively setting this pin high.  Setting the status pin high while the input pin is high resets only the fault state and not the current limitation trigger. Setting the status pin while the input pin is  low resets the fault state AND the current limitation trigger. I don't see that setting the status pin to low actually turns off the BTS3011.

Can you enlighten me about this?

And another question: Do I need to lower the value of Rstatus (10k) when I use three devices in parallel?

Kind regards,

Paul

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Xiangrui
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Hi Paul,

 

1. when overtemperature occurs (thermal shunt down temperature achieved), the Stauts is set low. Now the device will be turned OFF, even if the INPUT is High.

If input stays high and at the same time the temperature is lower than hysteresis threshold temperature, the device will turn on again after a delayed time tD(RESTART). 

It means, if the Input and Stauts both are low, then the device will stay OFF (It's easy to understand.)

Attention: Reset current limit trigger by „STATUS=high“ and „IN=low“ and „DMOS off (IL=0A)“.

After reset, the Status becomes Low.

It means, the Status will stay High for at least one period when overtemperature occurs.

2. 10k pull-up resistor is compatible for one and multiple devices parallelized.

 

BR,

Xiangrui

 

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Woody
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Hi Xiangrui,

2) Thank you.

1) What I was confused about in your very first answer is that you stated that when I connect the 3 status pins of 3 BTS3011's in parallel, if one of them overheats, all of them switch off.

To end my confusion I tested this a moment ago.  If I actively lower the STATUS pin of a BTS3011 (with pin IN high,  pin OUT active and the device @ normal temperature) this has no effect on its output. It does not shut off. This is in line with what I would expect from the data sheet but contrary to what you stated, at least how I understood that.

Kind regards,

Paul

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Xiangrui
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Hi Paul,

Thanks for pointing out this. The temperature over TJ(SD) or current limit trigged could be a precondition for shuntdown besides Status.

I'm going to check if the device will turn OFF at normal temperature but with a low Status signal.  

Best regards,

Xiangrui

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Xiangrui
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Hi Paul,

I checked the internal circuit of BTS3011TE. Your understanding is correct, sorry for confusing you.

The Status signal is only regarded as feedback for MCU and has no influence on gate driving unit. 

So, it can turn OFF the switch, if even MCU doesn't adjust the PWM signal on IN pin with Status signal (IN=High with Overtemperature).  

However, what I wanted to remind is that MCU cannot recognize which switch is in fault mode if you parallelize three switches with same Status.

Best regards,

Xiangrui

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Woody
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Hi Xiangrui,

Thanks for following up on this. Nice to know I understood correctly 🙂

Important for me is that in the BTS3011 the fault situation is latched until reset. So even when the temperature comes down and the failure itself is gone I have to reset the fault by setting the STATUS pin high. Parallelizing three STATUS pins means  that the MCU port has to source a max current of 21 mA to get this done. That is borderline comfortable for me so I might use an extra transistor to take the load off the MCU. Introducing this circuit uses an extra MCU pin, so that makes me rethink  the reason why I parallelized these pins in the first place: saving MCU pins.  I will either bite the bullet and change the 28 pin MCU for a 48 pin model and give every BTS3011 in this design (6 in total) its own STATUS port on that, or parallelize the 6 BTS3011 and introduce a reset circuit that can source the 42mA needed for resetting them all together. Functionality wise this is no problem; whenever one of the BTS3011 overheats, all have to be switched off anyway.

Thanks for helping me order thoughts on this.

Kind regards,

Paul

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