Re: 如何减小charge pump的电流失配？
时间：12-11
整理：3721RD
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一般说来,全差分结构比单端结构的匹配要好的多,如果功耗或者loop filter不允许的情况下,可以有:
1).error amplifier + reference current
2).replica + feedback
3).replica cp
等很多技术,paper都可以查到,就记得perrott的synthesizer里用的是第二种技术,但是功耗小不了,电压也不能太低,如果需要低压,看一下Charge pump with perfect current matching子characteristics in phase-locked loops, EL00
1).error amplifier + reference current
2).replica + feedback
3).replica cp
等很多技术,paper都可以查到,就记得perrott的synthesizer里用的是第二种技术,但是功耗小不了,电压也不能太低,如果需要低压,看一下Charge pump with perfect current matching子characteristics in phase-locked loops, EL00
"charge pump with perfect current matching ..."这个结构里用一个运放来保证电流匹配，我自己仿了一下觉得比较悬...那个运放很有可能会通过反馈来改变CP的输出电压。这样会给CP的输出带来更多的扰动。
error amplifier + reference current----is it also called 'servo amplifier'?
I use this structure, simulation shows that it really helps matching. See <A frequency synthesizer for multi-standard wireless applications>, Hong Jo Ahn, SMEE, The Ohio State University
By the way, even best structure gives some unmatching between P and Nmos. Sometimes We need to bring in static-phase-error so as to set the lock-point at the most linear zone in the PFD-CP transfer function curve.