SNVSBJ0B December 2019 – August 2021 LM5170
PRODUCTION DATA
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, 12-V rail UVLO, or VCC UVLO.
Assume you implement 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 8-29 and Equation 21, you can find that RUVLO1 is given by:
The final selection must select the closest standard resistor of RUVLO1 = 86.6 kΩ.
And RUVLO3 must satisfy Equation 23, namely,
Select the closest standard resistor, RUVLO1 = 976 Ω.
If you choose 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.