An Integrated 1.2V-to-6V CMOS Charge-Pump for Electret Earphone

Abstract

To reduce the chip size and guarantee the reliability of This work proposes a new charge pump design that pumping capacitors, the Cockcroft-Walton-based multiplier achieves a high set-up ratio for electret earphone driving cell [2] with strong-inversion MOS capacitor is adopted. But circuits. The voltage pumping cell is based on due to the low system supply voltage, the effective value of Cockcroft-Walton topology to achieve small area with constant MOS capacitor decreases since it may be away from strong MOS capacitor value under low system voltage operation. A inversion. A new topology of voltage multiplier is proposed 6-V output voltage is regulated by a PFM-based loop. This loop thereof in order to accomplish the pumping circuit with high includes a new switched-capacitor divider as a part of the step-up ratio. Fig. 2(a) shows the topology of the voltage sensing circuitry. All the components are integrated in a multiplier. Dashed line encircled is a unit pumping cell. Cl and standard 0.18ptm CMOS. Measurement results show that with C2 have to provide the required charge to the next stage. Two 1.2V supply, the output voltage is around 6V with 3OmV output smaller series capacitors Cal and Ca2 are connected to extend ripple. The maximum output driving current is up to 0.7mA. the cross voltage of C1 and C2. There are two out-of-phase clocks Clkl and Cjk2 to drive the cell. As depicted in Fig. 2(c), at Ky rs hig netup-ratioharged circuit, ephase 1, when Clkl is high and Cjk2 is low, C1 pushes the charge earphone, CMOSintgrato the output, C al pushes the charge to C2, and Ca2 is charged by System Description the system supply voltage Vm. At phase 2, the bottom plate of Ca2 is switched to Vm . The cross voltage of C1 is therefore equal Electret earphones are suitable for portable audio systems. Bonot require to the summation of the cross voltage of Vm and Ca2, which is Beids heexelen aouti prfrmnc, t oe2Vmn. The effective capacitance value of C1 will not degrade tens of mA to drive dynamic type coils or hundreds of volt to drn dischare pas ith tiane nt Tegsame vibrate electrostatic type films. In our application, with a new oprin cange ap e for C2 is are un e site electret structure[1], the driving current can be reduced asdud asi 500 .A with the driving voltage of 6V to activate the static phase. By cascading more pumping cells higher set-up ratio is achieved. In this design three pumping cells are used to get force. The charge pump circuit revealed in this paper is to supply audio driver with 6-V output from a single 1.2V battery. set-up ratio of seven. Fig. 1 shows the system overview of the proposed chargeCIk CIk2 V0-7Vjn HighVoltage Reliable Phase-I Vo-7Vj, pump. In addition to the voltage multiplier cells, a pulse Q l Q frequency modulation (PFM) control loop that includes a C5 6 6 voltage sensing circuit, a gated ring oscillator and a digital Ca5 Ca CA e 1Q Q controller is integrated. This loop asynchronously regulates the cl L 5Qt Q output voltage level to keep small power dissipation under light 4 load con...

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