1, the range of application of charge pump Mobile phones, cordless phones, walkie-talkies and other portable communications products are the use of batteries as a power supply, the rational use of the battery to fully tap its potential to improve efficiency and extend battery life. The LCD screen of the mobile phone needs a high-brightness white LED to light up. The white LED needs a stable 5V working voltage. If the working voltage drops, the brightness of the white LED is reduced and the color is not clear. The display effect of the LCD color screen is not satisfactory. White LED can not be directly powered by the battery, because the battery started to use, the voltage decreases, the impact of display. Therefore, the circuit design requires the use of a step-up charge pump to drop the voltage in a long period of time stable at 5V. Charge pump for mobile phones, PDA, E Book, flat panel displays, smart card reader, USB5V power supply, GSM mobile phone SIM interface power supply. 2, the classification of charge pumps, working principle and typical application circuit 2.1, charge pump classification Charge pump can be divided into: switch regulator booster pump without adjusting the capacitive charge pump can be adjusted capacitive charge pump 2.2, the working process of three kinds of charge The pump works by first storing the energy and then releasing the energy in a controlled manner to obtain the desired output voltage. Switching regulators booster pumps use inductors to store energy, while capacitive charge pumps use capacitors to store energy. Capacitive charge pump through the switch array and oscillator, logic circuit, compare the controller to achieve voltage increase, the use of capacitors to store energy. Due to the higher frequency of operation, the use of small ceramic capacitors (1μF), occupy the smallest space, lower cost. The charge pump can provide ± 2 times the output voltage with only an external capacitor. The losses come mainly from the capacitor's equivalent series resistance (ESR) and the internal switching transistor's RDS (ON). The charge pump converter does not use an inductor, so its radiated EMI can be neglected. Input noise can be filtered with a small capacitor. Its output voltage is factory-preset precision and can be adjusted via a back-end on-chip linear regulator, so the charge pump can be designed to increase the number of switching stages of the charge pump to provide sufficient activity for the back-end regulator space. Charge pumps are ideal for portable applications. The internal structure of a capacitive charge pump is actually a system of reference, compare, convert and control circuits. 2.3, several different charge pump applications AAT3110 output parallel power supply, less external components, alignment is simple, high conversion efficiency. AAT3110 micro-boost power charge pump is the United States Yannuo Logic Technology Co., Ltd. (AATI) developed micro-power switch capacitor voltage boost converter. It provides a stable 5V output voltage with no other inductor necessary for operation of the booster pump and only three small ceramic capacitors on the periphery. It can output 100mA current, can drive 4 ~ 5 white or blue LED, in order to meet the color LCD backlight application. AAT3110 is characterized by small quiescent current, high conversion efficiency, load capacity, is ideal for battery power applications. The AAT3110 operates from a high-frequency boost of 750kHz and uses pulsed-hopping to extract a stable output voltage from a varying input voltage. Input voltage range of 2.7V ~ 5.5V, 5V output voltage stability, the conversion efficiency of more than 90%, output ripple much smaller than similar products, ESD is greater than 2kV, with short circuit protection, over-temperature protection. The AAT3110 consumes little power, at only 13μA, with less than 1μA in shutdown. Compared with similar products of other companies, AAT3110 has large output current, small ripple and low price. It can supply power to parallel LED in practical application. It has less wiring and easy to use, so the process cost is low. The external circuit does not use inductors, EMI radiation. AAT3110 Main technical parameters: - Operating voltage Vin = 2.7V ~ 5.5V - Output voltage Vout = 5.0V / 100mA - Quiescent current Iq = 13μA - Shutdown current ISHDN = 1μA - More than 90% Operating Frequency 750kHz - Package SOT23.6SC70JW-8 The AAT3110 is available in a small, 6-pin SOT23 package for surface mounting and occupies little space on the PCB. SC70JW is AATI patented ultra-small 8-pin package shown in Figure 6, the duty cycle of up to 42%, occupying PCB area of ​​only 4.2mm2, the chip lifted the installation of natural air can be heated to heat, more than 3 feet grounded Use PCB cooling. The AAT3111 is a similar micropower boost charge pump. Its operating voltage is 1.8V ~ 3.3V / 3.6V, stable output of 3.3V or 3.6V, current 100mA, the most suitable for the use of two batteries as the power supply products. 3 Charge Pump Selection Points As a design engineer, the following requirements should be considered when choosing a charge pump: 1) Higher conversion efficiency - No adjustment Capacitive charge pump, 90% - Adjustable capacitive charge pump, 85% - On-off Regulator, 83% 2) quiescent current is smaller, you can more power 3) the input voltage is low, the potential of the battery as much as possible 4) the noise is small, the overall circuit of the phone without interference 5) Improve the use efficiency of the unit area, make the mobile phone design more compact 6) sufficient output adjustment capability, the charge pump will not overheat due to work at full capacity 7) small package size is a universal requirement for portable products 8) low installation costs, Including less peripheral circuits, PCB board area is small, less alignment and simple 9) with a closed control side, the charge pump can be turned off in a long standby state, the current consumption close to zero