米6体育平台手机版

ZHCSM29A September 2023 – June 2024 LM70840-Q1 , LM70860-Q1 , LM70880-Q1

PRODUCTION DATA

请参考 PDF 数据表获取器件具体的封装图。

Use Equation 31 to calculate the required buck inductance based on a 40% inductor ripple current at nominal input voltages.
Equation 31. $L_{O} = \frac{V_{O U T}}{Δ I_{L O} \times F_{S W}} \times (1 - \frac{V_{O U T}}{V_{I N (n o m)}}) = \frac{5 V}{3.2 A \times 400 k H z} \times (1 - \frac{5 V}{48 V}) = 3.5 µ H$
Select a standard inductor value of 3.3µH. Use Equation 32 to calculate the peak inductor currents at maximum steady-state input voltage. Subharmonic oscillation occurs with a duty cycle greater than 50% for peak current-mode control. For design simplification, the LM70880-Q1 has an internal slope compensation ramp proportional to the switching frequency that is added to the current sense signal to damp any tendency toward subharmonic oscillation.
Equation 32. $I_{L O (P K)} = I_{O U T} + \frac{∆ I_{L O}}{2} = I_{O U T} + \frac{V_{O U T}}{2 \times L_{O} \times F_{S W}} \times (1 - \frac{V_{O U T}}{V_{I N (m a x)}}) = 8 A + \frac{5 V}{2 \times 3.3 µ H \times 400 k H z} \times (1 - \frac{5 V}{60 V}) = 9.74 A$
Based on Equation 8,use Equation 33 to cross-check the inductance to set a slope compensation close to the ideal one times the inductor current downslope. The selected 3.3µH has less downslope and be adequate.
Equation 33. $L_{O (s c)} = \frac{V_{O U T} \times R_{S}}{24 \times F_{S W}} = \frac{5 V \times 5 m Ω}{24 * 0.4 M H z} = 2.6 µ H$