SNVSBJ0A December 2019 – June 2020 LM5170
The example circuit uses the UVLO pin as the master enable pin of the LM5170. However, the UVLO pin can also fulfill the function of undervoltage lockout, either the 48-V rail UVLO, or 12-V rail UVLO, or VCC UVLO.
Assume the user implements the 48-V rail UVLO, and the low-side resistor RUVLO2 = 10 kΩ, the 48 V UVLO release threshold VUVLO = 24 V, and UVLO hysteresis is VHYS =2.4 V. Referring to Figure 47 and Equation 21, one can find that RUVLO1 is given by:
The final selection should select the closest standard resistor of RUVLO1 = 86.6 kΩ.
And RUVLO3 should satisfy Equation 23, namely,
Select the closest standard resistor, RUVLO1 = 976 Ω.
If the user chooses to add the capacitor CUVLO = 1 nF, it leads to a delay time constant of 10 µs to filter possible noise at the at the UVLO pin.