应用于轨到轨运放的一种低纹波电荷泵

A low ripple charge pump for Rail-to-Rail Op amp applications

运放电路通常采用互补差分输入对的方式实现轨到轨输入,但输入级跨导的波动增大了运放设计难度。针对轨到轨运放输入级跨导恒定的问题,设计了一种宽输入范围低纹波电荷泵。利用振荡器产生时钟信号,控制数字逻辑电路,生成五对时钟不交叠的开关控制信号,来交替开启和关闭泵电容,在开关交替期间对泵电容进行预充放电,从而规避时钟馈通效应,降低输出纹波。电路使用0.35μmBCD工艺。仿真结果表明,在时钟频率为10MHz、负载500μA时,电荷泵输入电压2~5V,输出均可提升1.5~1.6V,输出纹波低于3mV,提高了电路内部电源的稳定性。

The op amp circuit usually uses complementary differential input pairs to achieve Rail-to-Rail input,but the fluctuation of input stage trans-conductance fluctuation increases the difficulty of op amp design.To address the problem of constant trans-conductance of the Rail-to-Rail op amp input stage,a wide input range low ripple charge pump is designed.An oscillator is used to generate a clock signal and control a digital logic circuit to generate five pairs of clock non-crossover switching control signals to alternately turn on and off the pump capacitor and pre-charge and discharge the pump capacitor during the switching alternation,thus circumventing the clock feed-through effect and reducing output ripple.The circuit uses a 0.35μm BCD process.Simulation results show that at a clock frequency of 10MHz and a load of 500μA,the charge pump input voltage of 2~5V,the output can all be boosted by 1.5~1.6V,and the output ripple is less than 3mV,improves the stability of the circuit’s internal power supply.