TCAN4550-Q1: UVLO and Vsup=5.5V

Erick,

Thank you for your reply!

I understand your answer.
But I'm concerned about 5.82V, not the minimum ripple voltage, but the average value in steady state.

In the latter case, the UVsup(rising ramp) threshold has not been exceeded.
Is there no problem?

Best Regards,

Kaede Kudo

Kaede,

I looked at some characterization data for this device across 3 lots and 3 temperatures (-40C, 25C, and 125C). In all cases, the maximum UVVSUP rising was 5.51V, with the average value ranging from 5.45V to 5.48V. This falls in with the typical value shown in the datasheet, and while I can't guarantee that every single device will follow this, the data shows that the true UVVSUP rising voltage is much closer to the typical value in the datasheet (5.5V) than it is to the maximum value (5.9V).

I don't think this will be a problem if the voltage does indeed stay at 5.82V during steady state.

Regards,

Eric, 

Thank you for your cooperation.

I understood that UVvsup rising falls in typical value.
I think so.

But guarantee value is 5.9V(max).
What is the basis for the above value?

If Vsup does not meet UVvsup's requirements at power-on, the device will not start up, so I think the maximum value of UVvsup rising is a very important specification.
Customers will not be able to consider the Typical value alone.

UVvsup rising does not match Recommended Operation Conditions.
Recommended Operation Conditions should indicate the range in which the device operates normally, but if UVvsup rising is referenced, the device may not start up.

First of all, I want to know if the maximum value of 5.9V is correct.
If it is correct, it is inconsistent with Recommended Operation Conditions's Vsup, so please answer whether it can be used at Vsup = 5.5V as a guaranteed value.

Best Regards,
Kaede Kudo

Kaede,

Thanks for the feedback, and I understand the confusion. The reason the UVVSUP threshold is 5.9V is to properly initialize the internal LDO. If the 5.9V threshold isn't crossed on initial power-up, the LDO won't start up so the device won't properly power on. 

Once the 5.9V threshold is passed, then the lower VSUP shouldn't be a problem unless it falls below the UVVSUP falling threshold (4.7V). If this happens then the device will go into UVLO.

From the description of the customer's system, this shouldn't be problem. The voltage will rise to 6V, passing the 5.9V UVVSUP rising threshold to start up the internal LDO, then if it drops to 5.82 at the lowest, it will still remain on and functioning properly.

Thanks for you patience on this, my initial thought was that 5.5V was the threshold that needed to be passed for the LDO startup, but I was incorrect.

Please let me know if you have any other questions or concerns.

Regards,

Eric,

Thank you for your answer.

I understood that there was no problem once it exceeded 5.9V.

Thank you for your coopeartion.

Kaede