PIC 18F4550 PWM频率限制

我需要用一个18F45 50尽快切换FET。有了内部（8MHz）时钟，我被限制在31250Hz。我用数据表将一个48 MHz晶体连接到10pF电容器上（数据表只给出了20MHz的电容器例子），并配置了PIC来高速运行外部晶体（HS）。理论上，48 MHz的FoSC应该给出最大的PWM频率为48 MHz / 256＝187500赫兹，但我只得到62500赫兹。如果我拔掉水晶，PIC回复到它的内部振荡器，所以我必须把它设置好。我用的是18F45，因为这是我在其他地方用的手。我用CooRoft沃尔顿乘法器级制作一个升压电路，如果任何物体感兴趣，从10V获得600伏。



      以下为原文

    I am needing to switch a FET as quick as possible with a 18F4550. With the internal (8Mhz) clock I am limited to 31250Hz.

I hooked up a 48Mhz crystal as per datasheet using 10pF capacitors to ground (datasheet only gives capacitor example up to 20Mhz) and configured the PIC to run the external crystal at high speed (HS). In theory the 48Mhz FOSC should give a maximum PWM frequency of 48Mhz / 256 = 187500Hz but I am only getting 62500Hz.

The PWM isn't limited surely? If I unplug the crystal, the PIC reverts back to its internal oscillator so I must have that set up fine.

I am using a 18F4550 because it is what I have to hand as I use it elsewhere. I am making a boost circuit with cockroft-walton multiplier stages to get 600V from 10V if any body is interested.


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