SLVSEW6F August 2021 – March 2024 TPS7H2211-SEP , TPS7H2211-SP
PRODUCTION DATA
The TPS7H2211 eFuse is exceptionally well suited to provide overvoltage protection in this application. This is because even if the upstream regulator fails in a manner that shorts its input to output (12 V), the TPS7H2211 eFuse is able to handle up to 14 V at the input with full data sheet specified performance.
The overvoltage protection is set by configuring the RBOT_OVP and RTOP_OVP resistors similarly to Section 10.2.1.2.3. The overvoltage protection feature turns off the switch if the input voltage exceeds a predetermined value. For this design, the goal is to have the overvoltage protection activate at a nominal voltage of 5.4 V. First set RTOP_OVP = 100 kΩ with a 0.1% tolerance resistor, then use Equation 20 to calculate the nominal value of RBOT_OVP. A nominal 27-kΩ 0.1% tolerance resistor best satisfies the equation.
where
In order to ensure the selected RBOT_OVP value is acceptable for both the minimum and maximum OVP rising threshold, use Equation 21. VINOVP_RISE(MIN) is selected as the highest possible value that VIN will reach during nominal operation. VINOVP_RISE(MAX) may be selected by the user as long as it is within the VIN of the Recommended Operating Conditions. These selections result in an allowable value of RBOT_OVP between 9.214 kΩ and 27.791 kΩ. The selected 27 kΩ-0.1% tolerance resistor satisfies these constraints, even when taking into account its tolerance.
where
Since the OVP pin has hysteresis, the OVP falling threshold will be different than the rising threshold. Therefore, in order to ensure the selected RBOT_OVP value is acceptable for the OVP falling threshold, use Equation 22. VINOVP_FALL(MIN) and VINOVP_FALL(MAX) values may be selected using the same method as for VINOVP_RISE(MIN) and VINOVP_RISE(MAX). These selections results in an allowable RBOT_OVP value between of 9.128 kΩ and 27.154 kΩ. The selected 27 kΩ-0.1% tolerance resistor also satisfies these constraints, even when taking into account its tolerance.
where
To summarize, using Equation 3 and Equation 4 with RTOP_OVP = 100 kΩ and RBOT_OVP = 27 kΩ, the eFuse will nominally go into overvoltage protection mode at 5.41 V and exit at 5.36 V. Taking into account the minimum and maximum OVP pin threshold and resistor tolerances, the switch will enter overvoltage protection mode between 5.21 V and 5.56 V and exit between 5.12 V and 5.51 V.