ZHCSFO3D November 2016 – August 2021 LM5170-Q1
PRODUCTION DATA
The example circuit uses the UVLO pin as the master enable pin of the LM5170-Q1. 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 8-29 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.