Hello team,
Customer think VUVLO(HYS) would be calculated IUVLO(HYS) X RUV1 since IUVLO(HYS) = 20uA typ is for RUV1 not RUV2.
Why the equation 17 is used RUV2 not RUV1 ?
Thank you and best regards,
Michiaki
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Hello team,
Customer think VUVLO(HYS) would be calculated IUVLO(HYS) X RUV1 since IUVLO(HYS) = 20uA typ is for RUV1 not RUV2.
Why the equation 17 is used RUV2 not RUV1 ?
Thank you and best regards,
Michiaki
Hi Michiaki,
I think since the comparator is looking at 1.24V, once the bottom resistor is set then the current going through the Ruv1 is set, therefore the delta of 20uA hysteresis current will have to go through Ruv2
Thanks
-Arief
Hi Arief,
Could you kindly give me some more detail ?
Looking at functional block diagram in the datasheet, we see the constant current source at EN/UVLO comparator.
I understand that the current at 20 uA go through both RUV1 and RUV2 but I couldn’t understand why the equation is used RUV2 not RUV1.
Thank you and best regards,
Michiaki
Are there any concern if UVLO function is disable ?
Our customer concerns if there would be any malfunction due to lost the pass of IUVLO at 20 uA.
Thank you and best regards,
Michiaki
Hi Michiaki,
I speak with the application engineer who is in development of this device and he mentioned that
It is the differential 20uA from the input (Vin) to (En) across the Ruv2 which decides the hysteresis
If there is no 20uA therefore there is no hysteresis, the UVLO function is still there but may oscillate due to no hysteresis.
Thanks
-Arief
Hi Arief,
Why is hysteresis defined by Ruv2 not Ruv1 ?
Constant current source at 20uA is seen at EN/UVLO but I don’t think the current path is through Ruv2.
Thank you and best regards,
Michiaki
Hi Michiaki,
I think the best way is to test it on the EVM since i checked the datasheet and calculator uses Ruv2 as hysteresis.
Thanks
-Arief
Hi Arief,
We would like to know the mechanism why hysteresis can be determined by Ruv2
Thank you and best regards,
Michiaki
Hi Michiaki,
I did some simulation on this circuit and what stated in the datasheet is correct.
The hystereis is dependent upon Ruv2 and the reason being is because the internal comparator threshold is set to be fixed to be 1.24V.
Therefore you can think of that the mid point between Ruv2 and Ruv1 is somewhat "regulated" at 1.24V.
THis means the current on the Ruv1 will be constant with or without the hysteresis current.
Therefore the extra current that flows from the hysteresis will flow only to the top enable resistor Ruv2. I have the simplis file if you would like to check it out
Thanks
-Arief