Seektronics

In the peripheral circuit design of DC-DC BUCK chips, we usually add capacitors or a combination of capacitors + resistors between the BOOT and SW pins, this piece of circuit is called bootstrap circuit, the capacitors and resistors in the bootstrap circuit are called bootstrap capacitors and bootstrap resistors.   What is a bootstrap capacitor?   DCDC Buck chip has a pin called BOOT, and some are called BST. The following is an explanation of the BOOT pin of a DCDC chip. In the external circuit design, a capacitor, generally 0.1uF, is needed between the BOOT and SW pin, and is connected to the driver end of the high-end MOS tube of DCDC.     How does a bootstrap capacitor work?   The following is a block diagram of a DCDC BUCK chip, the top NMOS is called the high-side MOSFET and the bottom NMOS is called the low-side MOSFET.     When the high side MOS tube is turned on, SW is VIN, SW charges and stores energy in the inductor, and the inductor current is rising; when the low side MOS