TLV171-Q1: Is TLV171QDBVRQ1 Op-Amp Short Circuit Protected ?

Hi Kai,

I have gone through all of these sections.

But the main concern is how long it can withstand in terms of Tj(junction temperature) as I have mentioned my Ta(ambient temp.)=115degree cel. so with this Tj=Ta+(RthJA*PD).

Samrat Pushpesh

Hello Samrat,

Kai is correct. Section 6.1 states that the device can withstand a continuous short circuit current limit (provided it does not exceed the absolute maximum temperature rating). And Figure 24 shows how the short circuit current limit decreases over temperature. 

To calculate the temperature the device may heat up to based on a short circuit current limit I recommend watching our TI Precision Lab videos on Power and Temperature. The videos will show how to calculate the temperature of the device based on output current, output voltage, supply voltage, and ambient temperature.

Thank you,

Tim Claycomb

Hello Samrat,

I'm glad I could help! Please let us know if you have any additional questions.

Thank you,

Tim Claycomb

Hi Tim,

I have a query regarding the TLV171-Q1 op-Amp.

As you told me to go through the TI -Precision Lab Power temp video , so I watched the video and came to know about the thermal protection.

As per my analysis TLV171-Q1 is not thermally protected. so with my circuit condition I have calculated the Power dissipation and junction temperature which is going beyond my Tj=150 degree Cel.

I have attached the calculation and circuit diagram of opamp comparator with parameters(KL_30_PROT=36V)

Could you please verify whether I am doing correct or not?

Because if it is correct then if TLV171 don't have thermal protection then it will not work during Short to ground condition.

Please give you view or calculations, it will be really helpful.

Thanks 

Samrat Pushpesh

Hello Samrat,

I have a very big concern with how the TLV171-Q1 is being used in your design. Is the TLV171-Q1 being used to function as a comparator?

If so, your circuit will likely NOT function properly. This is because the TLV171 has internal back to back diodes which will turn on when the inputs of the op amp are pulled apart. Please see "Op Amps used as Comparators - is it ok?" for more information.

Are you open to using another op amp for your design? If so, please give me some basic requirements (supply voltage, bandwidth, automotive qualified, etc.) of your design and I will recommend a device to fit your needs.

Thank you,

Tim Claycomb

Hello Tim,

I have implemented one idea here to prevent this self over heating during short to Ground and  Short to Battery condition.

What I did, I have prepared one RC Analog input circuitry which will going to the microcontroller pin , ultimate work is to diagnosis whenever this Short circuit happen microcontroller will give command to cut the supply voltage . This is how I have proposed the thermal protection.

Is this a good solution? If not then recommend your suggested part no. for comparator op-amp.

My Supply requirement is Vs=36V

Should be AEC-Qualified. And Gain Bandwidth Approx. 3MHZ.

Thanks

Samrat Pushpesh 

Hi Samrat,

I'm not 100% sure the idea you proposed will work. The reason being is that there are also diodes from the output pin to V+ and V-. So if you turn off the supply voltage when the output pin is pulled to GND or Vbattery then one of those diodes may conduct and cause damage to the device due to current flowing through the internal ESD diodes. However, this all depends on what "turning off" means. Does this mean that V+ adn V- are pulled to GND or are they floating? When the supplies are off can whatever is supplying your V+ supply sink current (if its an LDO it likely cannot, See TI Precision Lab Videos on EOS)? I also recommend reading "The self powering device" for more information on what can occur when an input signal may be present when the supplies are "off".

I recommend taking a look at the LM2904B-Q1. I also recommend reading through "Application Design Guidelines for LM324/LM358 Devices". This app note discusses using the LM2904 as a comparator.

Thank you,

Tim Claycomb

Hi Tim,

Yes it means I am pulling down V+ pin to 0V.

thanks 

Samrat Pushpesh 

Hi Tim,

I mean input of non-inverting terminal of op-amp is pull down to zero. That is what i am doing.

May be this will work .Because as you told me to go through "The Self Powering device". Hence this condition is not the same .

Thanks 

Samrat Pushpesh

Hi Tim,

Thanks for your responses.

It was a very informative discussion.

Thanks 

Samrat