JAJSGX1G September 2006 – Jaunuary 2020 LM5069
PRODUCTION DATA.
In general, a lower-power limit setting is preferred to reduce the stress on the MOSFET. However, when the LM5069 is set to a very low power limit setting, it has to regulate the FET current and hence the voltage across the sense resistor (VSNS) to a very low value. VSNS can be computed as shown in Equation 7.
To avoid significant degradation of the power limiting accuracy, a VSNS of less than 5 mV is not recommended. Based on this requirement the minimum allowed power limit can be computed in Equation 8.
To avoid significant degradation of the power limiting accuracy a VSNS of less than 5 mV is not recommended. Based on this requirement, the minimum allowed power limit can be computed with Equation 9.
Note that the minimum RPWR would occur when VDS = VIN,MAX. We can then compute the minimum RPWR with Equation 10.
To obtain the smallest accurate power limit, the next largest available resistor must be selected. In this case a 15.8-kΩ resistor was chosen, which sets a 39.23-W power limit.