TPS3808G01: Vit hysterisis

Q: TPS3808G01: Vit hysterisis by 7482

The customer need to determine the worst case trigger window on an under voltage for the TPS3808G01. They are considering the resistor divider tolerances, reference tolerance, and hysteresis. The data sheet specifies a max. ±2% reference variation and a max. 3% hysteresis.

How does one interpret the hysteresis sepcification? Is it total and divide by two? Or is it 3% hysteresis in either direction?


A: Re: TPS3808G01: Vit hysterisis by 1090425

What is specified first is the negative going threshold.  This is +/- 1% typical and +/-2% maximum centered around the 0.4V reference voltage for the SENSE input.  This is when the signal on SENSE is going high to low.

Once the low level is reached (at a point within +/-2% of 0.4V), hysteresis is added to the SENSE input.  This SENSE input must exceed the same negative going threshold plus some hysteresis on top of it.  Thus, the hysteresis is specified as a positive value since it adds to the threshold voltage.  This positive going SENSE voltage threshold will be typically 1.5% above wherever the negative going threshold was.  It will be a maximum of 3% higher.

Once the SENSE input exceeds the negative going threshold plus hysteresis, the hysteresis is removed and the SENSE pin threshold returns to the (lower) negative going threshold value.