Abstract ▼ AI-Helper

The integrated DC-DC converter makes it appropriate for use in many applications, namely, portable, display, and cellular applications. The display driver circuit requires an integrated converter to power up digital logic circuits and to convert the unregulated DC input into a controlled DC output a...

The integrated DC-DC converter makes it appropriate for use in many applications, namely, portable, display, and cellular applications. The display driver circuit requires an integrated converter to power up digital logic circuits and to convert the unregulated DC input into a controlled DC output at a desired voltage level. The increasing demand is especially apparent in mobile battery–operated phones. In a cellular phone, for instance, switch-mode regulator is used to buck down and boost up the voltage. Low voltage operation is an intrinsic circuit characteristic for increased battery efficiency. A novel current sensing circuit for buck and boost converter is designed and fabricated with a 0.35㎛ BiCMOS process. The current mirror pair, power MOSFET, and sensing metal-oxide semiconductor transistors (MOSFETs) are used in the on-chip current sensing circuit. In order to match the low voltage of current mirror and obtain an accurate current sensing, folded cascode op-amp with a PMOS input pair is used in our design. A lateral double-diffused MOS transistor (LDMOST) switch is used to protect the current sensing circuit from the high output voltage. Compared to CMOS technology in an integrated converter circuit, BiCMOS technology can provide an advantage of high current-driving capability and amplifier gain. As its name implies, it combines bipolar and CMOS circuits on one IC chip. It is to combine the low power and high input impedance of CMOS with the high current-driving capability of bipolar transistor. Specifically, CMOS, although a nearly ideal circuit in many respects, has a limited current-driving capability. On the other hand, BJT is capable of large output currents by virtue of its much larger trans-conductance. The controller block in an integrated DC-DC converter usually includes an error amplifier, comparator, current sensor, and so on. The error amplifier and current sensor require a low on-resistance and high gain to obtain a signal of fast transient response and high sensing accuracy. BiCMOS technology is well suited for the implementation of high-performance circuits.