| With the developing of white appliance market, especially the innovation in the field of the cell-phone, portable equipment and the automotive illumination, the market of power management IC is confront with more and more chances and challenges, has a fast increasing trend. Power management product presents a good many characteristics, such as a short design cycle, little occupied area, low power loses and high efficiency.At present, DC-DC converter and linear current regulator (LDO) are the two dominant products in the market. LDO, for its briefness, low noise and EMI, fast transient response, mini bulk and inexpensive, is well suited for back lighting of LCD panel and automotive illumination fields.In this paper, the design of a high_voltage, 350 mA, LDO linear current regulative HB LED driver is demonstrated. According to the functions the IC should have, the structure and functional blocks of the system were determined, and the direct schematic design of some subcircuits had also been conducted in reference to other function-like circuits.Then, the whole chip simulation and verification were conducted to examine the matching between the design and the requirements of specification. This paper put emphasis on the improvement on efficiency and accuracy of the linear current regulator, especially on the design of some critical blocks, such as reference and voltage regulator block, differential sense amplifier block and PMOS pass element block.This paper contributes mainly in the following:1. Presents a second-order curvature compensation method of bandgap reference, introduces a very simple and practical trimming method.2. Sets up a low current-sense reference, which achieves great improvement on efficiency.3. Decrease the value of low-dropout voltage of the chip by an improvement on the layout of PMOS pass element.The chip is designed and fabricated in Jazz 0.5μm BCD process. Simulation results proved that every electrical characteristic meets the design specification. |
PDF Full Text Request