LM3489 Vout ripple相关问题，请帮忙！

建议先看看资料

The LM3489 is a high efficiency PFET switching regulator controller that can be used to quickly and easily develop a small, cost effective, switching buck regulator for a wide range of applications. The hysteretic control architecture provides for simple design without any control loop stability concerns using a wide variety of external components. The PFET architecture also allows for low component count as well as ultra-low dropout, 100% duty cycle operation. Another benefit is high efficiency operation at light loads without an increase in output ripple. A dedicated Enable Pin provides a shutdown mode drawing only 7µA. Leaving the Enable Pin unconnected defaults to on.Current limit protection can be implemented by measuring the voltage across the PFET’s RDS(ON), thus eliminating the need for a sense resistor. A sense resistor may be used to improve current limit accuracy if desired. The cycle-by-cycle current limit can be adjusted with a single resistor, ensuring safe operation over a range of output currents.

http://www.ti.com.cn/product/cn/lm3489

LC滤波可以有效的减小输出电压的纹波，但参数要选的比较合适效果才比较好。其他的要注意开关频率，也会对输出电压纹波产生影响。

hysteretic mode DC-DC的纹波的确会大一点，你如果只是加大输出的L,C参数的话，还不一定能够搞定，看一下加大环路的带宽能够起到作用？

电感电容滤波网络可以有效减小纹波，但是也有可能是其它原因，比如PCB布板等因素。

增加电感电容滤波网络的确会改善滤波效果，但同时要注意，电感电容的加入可能会给电路带来其他的问题。设计时要选择合适的参数。

后续加LC网络肯定可以有效减小ripple，但是改善的程度要适情况而定，设计问题也可能导致ripple大。

加电感和电容网络去滤波是很经典的方式，所以不用怀疑这种方法了！

还可以改一下环路的吧！

加电感电容滤波肯定能减小的，不过还跟电感电容选型上要下功夫了。另外如果频率高的话，pcb布线的时候也有讲究的。