Part Number:SM72445
Hi TI-Team,
I'm working on a design with SM72445 and I found your document AN-2124 Power Circuit design for the buck boost topology.
I checked the calculations and I think I found a mistake.
The input capacitance of the boost part is given by C_in = \Delta Q_BST / \Delta V_in (beeing the electric charge and the ripple voltage on the input). Furthermore the electric charge is calculated with \Delta Q_BST = D_BST * V_mpp / (8 * f_s^2 * L) ( beeing the boost duty cycle, the in put MPP-voltage, the switching frequenz and the inductance used).
The document concludes with C_in = V_out - V_mpp / (8 * f_s^2 * L * \Delta V_in).
Ich think the wrong duty cycle was used and it should rather be C_in = (V_out-V_mpp) * V_mpp / (V_out * 8 * f_s^2 * \Delta V_mpp * L)
Am I missing something here?
All the best,
Frieder