MP1542 – 700KHz/1.3MHz BOOST CONVERTER WITH A 2A SWITCHSelecting the Output CapacitorSelecting the Inductor The output capacitor is required to maintain the The inductor is required to force the higher DC output voltage. Low ESR capacitors are output voltage while being driven by the input preferred to keep the output voltage ripple to a voltage. A larger value inductor results in less minimum. The characteristic of the output ripple current that results in lower peak inductor capacitor also affects the stability of the current, reducing stress on the internal regulation control system. Ceramic, tantalum, or N-Channel.switch. However, the larger value low ESR electrolytic capacitors are inductor has a larger physical size, higher recommended. In the case of ceramic series resistance, and/or lower saturation capacitors, the impedance of the capacitor at current. the switching frequency is dominated by the A 4.7µH inductor is recommended for most capacitance, and so the output voltage ripple is 1.3MHz applications and a 10µH inductor is mostly independent of the ESR. The output recommended for most 700kHz applications. voltage ripple is estimated to be: However, a more exact inductance value can ⎛ ⎞ be calculated. A good rule of thumb is to allow IN V - 1 × ILOAD ⎜⎜ ⎟⎟ the peak-to-peak ripple current to be ⎝ OUT V ⎠ ≈ RIPPLE V