ZHCSLO0 数据表 | 德州仪器 TI.com.cn

ZHCSLO0B April 2023 – October 2023 TPS62874-Q1 , TPS62875-Q1 , TPS62876-Q1 , TPS62877-Q1

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RZV|24
- MPQF690A

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9.4.2.2 Selecting the Output Capacitors

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

Equation 38.

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 39.

C_{O U T (m i n) (r e g)} = (\frac{12.5 \times 10^{- 6} \times 1.5 \times 10^{- 3} \times 2.4 \times 10^{3}}{2 \times π \times \frac{56 \times 10^{- 9}}{3} \times \frac{2.25 \times 10^{6}}{4}}) (1 + \sqrt{20 %^{2} + 10 %^{2}}) F = 835 μ F

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

Equation 40.

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 41.

C_{O U T (m i n) (s a t)} = \frac{1}{19.25 \times 10^{- 3}} (\frac{\frac{56 \times 10^{- 9}}{3} \times {(46 + \frac{2.4}{2})}^{2}}{2 \times 0.875} - \frac{46 \times 1 \times 10^{- 6}}{2}) (1 + 20 %) F = 25.7 μ F

In this case, choose C_OUT(min) = 835 µF, 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 1670 μF.