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TLV3701: TLV3701 damage cause

Part Number: TLV3701
Other Parts Discussed in Thread: TLV3401, LMC7221

Hello,

I've been working with the circuit below, which uses the TLV3701 comparator, in order to create a small start pulse:

My problem is that after one test, the component is damaged and I have to change it. I have suspected that any of the input currents could be damaging the component, but I can't find the cause reading the datasheet. The P15VDC power supply is a DC/DC converter, but I think that it doesn't have any problem.

Hope you could help me.

Thank you very much.

  • The 1N750 is a 4.7 V Zener diode. With the 500 Ω resistor from the 15 V supply, it tries to draw a current of 20 mA, which exceeds the TLV3701's absolute maximum rating.

    Why 500 Ω? What drive strength do you need at Vout? Wouldn't a 2:1 voltage divider (e.g., 200 kΩ and 100 kΩ) suffice?

    The easiest way to level-shift the output signal is to use a comparator with open-drain output, e.g., TLV3401 or LMC7221.

  • Hi Clemens,

    thank you very much for your answer.

    Is not because of the driver strengh, but for the timing considerations.

    We need that the Vout signal drives a HIGH (<2V is enough) before the V15VDC is totally stablish, as quick as we can. If we put a resistor divider, the output voltage could not be enough at that time.

  • R5 does not affect the timing. Just make it larger.

    I did not ask to replace the comparator, bust just to replace R5+D1 with a voltage divider R5+R6.

  • Hi Clemens.

    Thank you for your answer.

    I think that I couldn't explain correctly my problem. If I add a divisor resistor, the output gain will be smaller, so we'll see the 2V output later than with the direct output. I am sorry if I cause some misundertanding between the comparator time response and this issue. Nevertheless, following your advice, I have augmented the output resistor value in order to make the output current smaller, but I couldn't fix the problem.

    I have changed the perspective, and I've tested the circuit with a 5VDC power supply and discarting the output diode, and the comparator stills alive, so I guess that the output current was the problem. Now I have the following circuit:

    The output is not totally stable nor correct, although the component is not damaged. I am thinking about adding a quick discharge architecture to the input capacitor and some hysteresis in order to fix this.

    Thank you so much for your help.

  • Hello,

    It is being damaged because you are exceeding the input range. The supply voltage of the comparator is 5V, and the inverting input has 15V on it continuously.

    The TLV3701 does allow input voltages up to 5V above V+, or 10V in your case ....but see the problem? You are 5V over the limit. I am not surprised it is being damaged. And that is why when you go down to 5V it "survives".

    Also, when the power supply collapses, C2 has the full 15V on it, and will discharge (at hundreds of mA) into the input.  Because of the unique input design to allow this, damage can occur to the input stage when Vin > (V+) + 5V as there are no ESD clamps to clamp the inputs to V+ and you coud be applying up to 15V above V+. Again...see the problem?

    You need to scale the input voltages to below 5V. A resistor in parallel with C2 can create a 1/3 voltage divider, and the values of the resistors scaled-up to create the same time constant with C2. R3 and R4 can be adjusted to change the threshold.

    And, as Clemens showed, 20mA is a bit much for a nano power comparator.

  • Hi Paul,

    thank you so much for your explanation. At yesterday tests I detected tha input over-range, so I think I'll try with your solution!

    Thank you to everyone for your help.