TLC7705M: Threshold Voltage (VIT+) of TLC7705

May

Part Number: TLC7705M

Hi Team,

Customer is looking for the Threshold Voltage (VIT+) of TLC7705. Below is the inquiry.

"I am trying to find the upper threshold voltage, VIT+, of the SENSE pin that causes the RESET outputs to change value. I have only been able to find a value for VIT- on the datasheet. And how long of a time does the input to SENSE need to be above the threshold for it to trigger the RESET outputs to change?"

Regards,

Maynard

over 3 years ago

+1 Ben C over 3 years ago

TI__Mastermind 38435 points

Hi Maynard,

TLC7705 has a threshold voltage of 4.55V. It is defined, although it is not stated in the datasheet for some odd reason, that VIT+ = VIT- + Vhys. Therefore, the TLC7705 has a VIT+ = 4.55V + 70mV = 4.62V.

I hope I have answered your question. Please click on "resolved" if there are no further questions. Thanks!

Ben

+1 Ben C over 3 years ago in reply to Ben C

TI__Mastermind 38435 points

Hi Maynard,

I forgot about your second question. See below:

Ben

0 May over 3 years ago in reply to Ben C

TI__Genius 9880 points

Hi Ben,

Thank you for your kind response. Customer has a follow up question regarding this.

"Follow-up question: we have a product with a 5V supply feeding into the TLC7705MJG. It is constantly between 4.8 and 5.3Vdc, well above the 4.62 threshold. I am monitoring pin 5 which is always high when the input stays in this range. From what I understand, the pin 7 voltage is above threshold and should drive pin 5 low, but it does not. So I must be misunderstanding something. However, when we get noise on our circuit that causes the supply voltage (pin 7) to spike over 6Vdc, the output of pin 5 goes low ~300us later. Do you know why pin 5 only drives low after these large spikes rather than constantly?"

Thank you in advance.

Regards,

Maynard

+1 Ben C over 3 years ago in reply to May

TI__Mastermind 38435 points

Hi Maynard,

I believe the customer is not understanding the functionality of the part. When the SENSE pin goes above VIT+, the /RESET (pin 5) signal should be high which signifies not asserted. If the SENSE voltage falls below VIT-, then pin 5 should go low (asserted).

Regarding the voltage spike on pin 7, I am not sure why the /RESET is asserted for 300us. Can the customer provide a scope shot? Also, it is advised that if the SENSE line is noisy, a 0.1uF capacitor can be used to filter out the spikes.

Ben

0 Ben C over 3 years ago in reply to Ben C

TI__Mastermind 38435 points

Hi Maynard,

Any updates from the customer on this issue?

Ben

0 May over 3 years ago in reply to Ben C

TI__Genius 9880 points

Hi Ben,

Thank you for your support.

This answer the customer query.

Regards,

Maynard

0 Ben C over 3 years ago in reply to May

TI__Mastermind 38435 points

Hi Maynard,

Glad to be help! Good luck!

Ben

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TLC7705M: Threshold Voltage (VIT+) of TLC7705