Abstract
The miniaturization and multi-purpose is the portable electronic products trend of development, therefore requests the DC/DC switch to have high characteristics and so on efficiency, low quiescent current, small board level area, small volume and low cost. The traditional power source management is uses the inductance pattern the DC/DC switch, but along with industry the micron technology's development and the multi-layered ceramics big electric capacity's use, the electric charge pump's efficiency has the enhancement, therefore the electric charge pump not only moreover still obtained the widespread application in the low power loss in the big output current application. To the electric charge pump principle research's foundation, the paper used 0.6um the standard Bi-CMOS craft to suppose teaches one kind to have the wide input voltage scope and the multi-electric current output specification constant flow electric charge pump DC/DC switch.
The input voltage scope is 2. 7V-5. 5V, the output voltage constant is 5. 1V, the output current is 1. 2A, 400mA, 240mA two kind of specifications. In the idling situation, the quiescent current is 5mA; In shuts off in the situation, quiescent current small ten luA. This article designs the linear electric charge pump constant voltage chip mainly applies in 5. 1V low pressure electric power supply. Its main body construction is composed of 2 time of electric charge pump electric circuit and the LDO linear voltage dropping voltage-stabilizer circuit. When battery's power supply ability is insufficient, when namely is lower than the rated voltage value of exports which needs, electric charge pump pump input voltage, maximum output value for input voltage two times. This output voltage after voltage-division resistance differential pressure, feeds back to the erroneous amplifier (AMP) cathode input end. Press source (REF) this voltage and the reference point to carry on the comparison, obtained the error voltage which enlarges. This error voltage serves as is controls the electric charge pump breakover resistance (to call that it controls resistance pressure), then obtained a stable output voltage.
This electric charge pump's merit is regardless of the input supply voltage is higher than or is lower than the output voltage, the output voltage can maintain constant through the automatic selection voltage dropping or the pressure-rise pattern. Pressure-rise and the voltage dropping pattern does not need the inductance part, may provide low EMI the DC/DC transformation. The high turn-on frequency permission selects the small superficial ceramics electric capacity, may save the board level area, reduce the cost and to reduce the output voltage ripple. Has the hot protection and the current limitation function, protects the work under the normal condition load part and the chip. Out-port the feedback loop adjustment output current which composes through the overload comparator causes its stable. Determines the voltage regulation and the electric current adjustment pattern through the 24mV comparator. This article has made the multianalysis to the electric charge pump DC/DC switch's basic principle and the system function, first introduced the overall construction, then introduced the partial submodule electric circuit with emphasis. In electric charge pump elementary theory, multianalysis linear (Linear) pattern, jumping cycle (SkipCycles) pattern; Simultaneously also introduced the electric charge pump's pressure-rise/voltage dropping principle of work as well as the main performance parameter and the significance. In the sub-electric circuit, introduced the band gap datum potential source, the operational amplifier, the undervoltage protection, the hot protection with emphasis. Each sub-electric circuit introduced the key job principle, the main parameter computational method and the simulation result separately. In the electric charge pump principle analysis and the sub-circuit design foundation, has carried on the simulation using the HSPICE simulation software to integrated circuit's key indicator and has given the detailed simulation result. The overall simulation result indicated that the electric charge pump's function and the important performance index achieves the design requirements.
key word: Electric charge pump, band gap datum source, operational amplifier, hot protection, undervoltage protection, soft start
