1.DC-DC降低EMI的技术,通常是使用扩频(Spread Specturm)和控制适当增大开关管的开启和关闭时间是吧?
2. DC-DC里面的Spread Spectrum Clocking功能一般默认是enable的么?如果默认使能状态,对其它芯片有干扰,
是不是会有很难滤波的问题?(因为Spread Spectrum默认enable状态,开关频率是随机改变的)
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HI
TI的DC/DC都是定频的(轻载为提升效率,会进入FPM模式,是变频率的),很多都是通过外部电阻来确认频率,也可以通过外部CLK同步频率。
关于EMI你还需要注意layout.
Hi
Pin脚定义:
COMP/FSET: Device compensation and frequency set input. A resistor from this pin to GND defines the compensation of the control loop as well as the switching frequency if not externally synchronized.
MODE/SYNC: The mode pin can also be used to synchronize the device to an external frequency. See the electrical characteristics for the detailed specification for the digital signal applied to this pin for external synchronization.