SNVSCE7B January 2024 – June 2024 TPS7H3014-SP
PRODUCTION DATA
At the system level the designer knows (or selects) the VONx and VOFFx levels. Usually these voltages are selected as percentages of the nominal rail voltage (VOUTx) being monitored. Knowing this information, we can calculate the resistive divider components values (RTOPx and RBOTTOMx) for the desired target levels. Using Equation 4 and Equation 5 we can calculate the top resistor as:
From Equation 1 we can calculate the bottom resistor as:
It's important to notice that the larger the separation between VONx and VOFFx (referred as VHYSx), the bigger the error in the off voltage. Figure 8-4 shows a plot of the error in the VOFFx for different hysteresis voltages (VHYSx = VONx – VOFFx). The plot is created for three different VON voltages (or percentages of the nominal output voltage: 90, 95, and 97% ) and two different output voltages (0.8V and 28V). As can be observed, the output voltage has very little impact on the off voltage error (differences cannot be appreciated on the plot). The error (in percent) can go from approximately 1% (at VHYS = 3%) to around 2.6% (at VHYS = 80%).