An RC filter is added to prevent any switching noise from interfering with the internal analog circuitry connected to VIN. The RC filter can be seen in the evaluation board schematic as components R_in and C_in. There is a practical limit to the value of resistor R_in as the VIN pin of the LM27402 will draw large bias currents to switch the gate of each MOSFET. If R_in is too large, the resulting voltage drop can disrupt normal operation. For the evaluation board, a 2.2-Ω resistor in conjunction with a 1.0-µF 25V X5R ceramic capacitor is used for the input RC filter.