• Resolved

# SN6505B-Q1: SN6505B-Q1 UVLO threshold max and min value

Part Number: SN6505B-Q1

Hi team,

Can you please provide SN6505B-Q1 UVLO max. and min value as datasheet only has max for VCC rising and min for VCC falling.

My customer is worst case analysis and they verifying at what VCC level will the device likely to be turn-on(VCC+ UVLO min) and what level of VCC will the device likely to be turn-off. (VCC- UVLO Max)

Thank you

Best Regards,

Wei-Hao

• Hi Wei-Hao,

Thank you for reaching out to us.

I understand that customer is trying to do worst-case analysis and I would like to mention that the data provided in datasheet is the worst-case data. The device can turn-on at any voltage point below 2.25V but 2.25V is the worst-case value. If customer considers 2.25V as the turn-on threshold for his analysis, then he will find that all the devices already turned-on at 2.25V and the datasheet guarantees this.
For analysis, if we assume the min UVLO+ threshold as 1.8V then it would mean that all the devices will turn-on anywhere between 1.8V and 2.25V. Here the min UVLO+ of 1.8V is of no significance as it doesn't say how many devices turn-on at this point. While the 2.25V point states that all devices are turned-on for sure at this point. Hence, 2.25V to be used as the worst-case guaranteed turn-on value for analysis.

Similarly, min UVLO- 1.7V is the worst-case turn-off voltage. The datasheet guarantees that all the devices will be turned-off when the voltage reaches 1.7V. This would be the right value to be considered for worst-case analysis.

Regards,
Koteshwar Rao

• In reply to Koteshwar Rao:

Hi Kote,

Long time no see and hope all is well. Thanks for your explanation, I understand specifying the max of rising can guarantee all device can be turned on above 2.25V and min of falling can guarantee all device can be turned off when VCC collapsed below 1.7V.

From the safety standard point, all safety action should be implemented prior the fault event to happen not after. Only knowing the all device will be turn-off below 1.7V has no significance at all to protect the system as device might be already stop working way above 1.7V and customer do not know at which VCC level they should take safety action because there is no max UVLO-falling value.

For example, let's assume the supply startup correctly all the way to 5V then the overload condition happened and VCC fell to 2.24V. Should customer take safety action when VCC fall at 2.24V? or at 1.95V (2.25V-0.3V = 1.95V)?

At 2.25V we can guarantee all device will be on, does that also mean 2.24V should be a safe point to run considering 300mV hysteresis? Or should customer assume anything below 2.25V has risk that some device can be turn off and take safety action?

Thanks.

Best Regards,

Wei-Hao

• In reply to Wei-Hao Chen (TW-FAE):

Hi Wei-Hao,

I understand the customer requirement better now. Customer basically needs to know at what voltage does device start turning OFF. They basically do not need guaranteed OFF voltage but the maximum voltage a device is likely to be OFF. I can try help you with that.

Worst-case UVLO+ is going to be 2.25V while the typical hysteresis is 0.3V. I will try to find out Hysteresis(min) between UVLO+ & UVLO- spec. UVLO+(max) - Hysteresis(min) should give us the UVLO-(max) spec. This would be the voltage below which a device can start to turn OFF.

Please allow me to come back to you on this. Thanks.

Regards,
Koteshwar Rao

• In reply to Koteshwar Rao:

Hi Kote,

Thanks and looking forward to your feedback. Much appreciated.

Best Regards,

Wei-Hao

• In reply to Wei-Hao Chen (TW-FAE):

Hi Wei-Hao,

Thank you for the wait. I have confirmed UVLO-(max) spec, it is going to be 1.98V. Thanks.

Regards,
Koteshwar Rao

• In reply to Koteshwar Rao:

Hi Kote,

Thanks for checking  UVLO-(max). Would you please help to check  UVLO-(min) as well? i.e. at which level the device might be starting to turn-on?

Cheers.

Best Regards,

Wei-Hao

• In reply to Wei-Hao Chen (TW-FAE):

Hi Wei-Hao,

I believe you meant to ask for UVLO+(min), this would be 1.97V. I am listing below all four parameters. Thanks.

1. UVLO+(min) = 1.97V, UVLO+(max) = 2.25V
2. UVLO-(min) = 1.7V, UVLO-(max) = 1.98V

Regards,
Koteshwar Rao

• In reply to Koteshwar Rao:

Hi Kote,