JAJSHD7 May 2019 TPS2596
ADVANCE INFORMATION for pre-production products; subject to change without notice.
The undervoltage lockout (UVLO) and overvoltage lockout (OVLO) trip point is adjusted using the external voltage divider network of R1, R2 and R3as connected between IN, EN/UVLO, OVLO and GND pins of the device. The values required for setting the undervoltage and overvoltage are calculated solving Equation 8 and Equation 9.
Where VUVLO(R) is UVLO rising threshold (1.2 V). Because R1, R2 and R3 leak the current from input supply VIN, these resistors must be selected based on the acceptable leakage current from input power supply VIN.
The current drawn by R1, R2 and R3 from the power supply is IR123 = VIN / (R1 + R2 + R3).
However, leakage currents due to external active components connected to the resistor string can add error to these calculations. So, the resistor string current, IR123 must be chosen to be 20 times greater than the leakage current expected.
From the device electrical specifications, VOVLO = 1.2 V and VUVLO = 1.2 V. For design requirements, VOV = 13.7 V and VUV = 8 V. To solve the equation, first choose the value of R3 = 47 kΩ and use Equation 9 to solve for (R1 + R2) = 489.58 kΩ. Use Equation 8 and value of (R1 + R2) to solve for R2 = 33.48 kΩ and finally R1= 456.1 kΩ. Using the closest standard 1% resistor values gives R1 = 464 kΩ, R2 = 33.2 kΩ, and R3 = 47.5 kΩ.