If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

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

Part Number: TLV171-Q1
Other Parts Discussed in Thread: TLV171, LM2904B-Q1, LM2904

I have a query regarding TLV171QDBVRQ1 Op-Amp short circuit current during short to ground condition at output side.

We are using TI’s Op-amp in our project where we have stuck in one condition.

In datasheet Isc=25mA written, so I wanted to know that is this op-amp short circuit protected?, If my supply voltage is 36V.

For how much long time period it can sustained this short to ground condition without surpassing the 150 degree Cel.  junction temperature . Our Ambient Temperature is 115 Degree Cel.

Please solve this query by providing the time period for it to sustain during SCG.

• Hi Samrat,

have you read section 6.1 of datasheet and the footnote (2)? Have you seen the "short-circuit current" specification in section 6.5 of datasheet? Have you seen figure 24 of datasheet?

Kai
• 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 Tim,

Now understood the scenario , thanks for your clarification also.

Thank You

Samrat Pushpesh

• Hello Samrat,

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.

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 Samrat,

There will be no issue with pulling the non-inverting input down to zero. This will cause the output to get as close as it can to the negative supply.

However, I recommend calculating the expected temperature under this condition again. Be sure to use the thermal specifications based on the op amp you have decided to use.

Thank you,

Tim Claycomb
• Hi Tim,

It was a very informative discussion.

Thanks

Samrat

• Hi Samrat,

I'm glad it was helpful. If you need further assistance in the future please let us know.

Thank you,

Tim Claycomb