TLV743P: What happens if the enable voltage is higher than Vin?

Hi Webber,

If the enable voltage is 1.5V higher than the input voltage, then the abs max rating is exceeded.  What is likely happening is the internal ESD diodes are forward biased and the key risk here is damaging those diodes as they are not designed to carry current.  Is there a current limiting resistor on the enable pin to the 3.3V rail?  If so, please let me know what value that is.  I can look into whether this external, current limiting resistance is enough to help lower the risk of a failure.  But be aware that it may not take a lot of current to damage the ESD diodes.

Thanks,

Stephen

Hi Stephen,

We placed a 6.1K ohm between 3.3V and the enable pin to limit the current.

Please help me to evaluate it if it will damage the enable pin, thanks.

Sincerely

Webber

Hi Webber,

I'll submit a request for a transistor level simulation.  Please be aware that these requests commonly take up to 2 weeks.  I'll reply back once I have additional data.

Thanks,

Stephen

Hi Stephen,

Got it, thanks.

Sincerely

webber

Hi Webber,

At this time we believe the 6.1k resistor limits the risk on forward biasing the ESD diode to a very low level. We are evaluating whether other internal circuitry can be damaged.  Thanks for your patience.

Thanks,

Stephen

Hi Stephen,

Thank you for the information, we're evaluating adding resistance to divide the enable voltage.

Please help to keep updating the simulation result, thanks.

Sincerely

webber

Hi Stephen,

Just want to follow up to find out if there's any update about the simulation.

Sincerely

Webber

Hey Webber,

We've made some progress on the simulation.  When tolerances are not considered, it appears Ven needs to be less than 1.7V above Vin.  But we are now running statistical simulations and I expect that number to change (I.E. go down).  I am hoping the statistical simulations will be complete in the next 1-2 days.  Thanks for your patience.

Thanks,

Stephen

Hi Stephen,

Got it, thanks.

Sincerely

Webber

Hi Webber,

What is the maximum junction temperature this device will see?

Thanks,

Stephen

Hi Stephen,

I am not sure what is the exact junction temperature.

I ensure the maximum output current is 101mA and, the voltage is 1.5V, the operating temperature of the product is -40C~+55C.

Could you use these information to calculate the maximum junction temperature?

Sincerely

webber

Okay thanks Webber, we'll estimate a worst case junction temperature increase of perhaps 10C.  This assumes 55C ambient air temp and something nearby that is also heating up the LDO slightly.  In reality it's probably half of this with your power dissipation.  We've been looking at 125C junction temperature which I suspect is more pessimistic than 65C. I've sent an email for the team to target closer to 65C which I hope will increase the allowed voltage.  Thanks for your patience, it's been a little bit of work to simulate at the transistor level the details we need to see for your question.  Please be assured that we are looking at this daily and hope to have some updates for you ASAP.

Thanks,

Stephen

Hi Stephen,

Got it, thank you and your team for the support.

Sincerely

webber