SLVSFU1 Data sheet

SLVSFU1C April 2023 – October 2024 TPS62874-Q1 , TPS62875-Q1 , TPS62876-Q1 , TPS62877-Q1

PRODMIX

10.3.2.2 Selecting the Output Capacitors

If the converter remains in regulation, the minimum output capacitance required is given by:

Equation 26.

C_{O U T (m i n) (r e g)} = (\frac{τ \times g_{m} \times R_{Z}}{2 \times π \times \frac{L}{N_{ϕ}} \times \frac{f_{S W}}{4}}) (1 + \sqrt{{T O L}_{I N D}^{2} + {T O L}_{f S W}^{2}})

Equation 27.

C_{O U T (m i n) (r e g)} = (\frac{12.5 \times 10^{- 6} \times 1.5 \times 10^{- 3} \times 1.5 \times 10^{3}}{2 \times π \times \frac{56 \times 10^{- 9}}{2} \times \frac{2.25 \times 10^{6}}{4}}) (1 + \sqrt{20 %^{2} + 10 %^{2}}) F = 350 μ F

If the converter loop saturates, the minimum output capacitance is given by:

Equation 28.

C_{O U T (m i n) (s a t)} = \frac{1}{∆ V_{O U T}} (\frac{\frac{L}{N_{ϕ}} \times {(∆ I_{O U T} + \frac{I_{L (P P)}}{2})}^{2}}{2 \times V_{O U T}} - \frac{∆ I_{O U T} \times t_{t}}{2}) (1 + {T O L}_{I N D})

Equation 29.

C_{O U T (m i n) (s a t)} = \frac{1}{25.6 \times 10^{- 3}} (\frac{\frac{56 \times 10^{- 9}}{2} \times {(24 + \frac{2.4}{2})}^{2}}{2 \times 0.8} - \frac{24 \times 1 \times 10^{- 6}}{2}) (1 + 20 %) F = - 41.5 μ F

In this case, choose C_OUT(min) = 350µF, as the larger of the two values, for the output capacitance.

When calculating worst-case component values, use the value calculated above as the minimum output capacitance required. For ceramic capacitors, the nominal capacitance when considering tolerance, DC bias, temperature, and aging effects is typically two times the minimum capacitance. In this case the nominal capacitance is thus 700µF.