superpro 280u IO 驱动问题 (2)

shangdawei

由于电容的存在, 当某引脚 VPP 开启的瞬间, 一个高压会通过电容加到 FPGA 的IO上
会损坏 FPGA 的 IO 吗 ?

shangdawei

liyf

这个问题该不能只是这个电路的理解，而是应该考虑集成电路的内部寄生电容，所以不能单独模拟这个电路，你可以实际测试下280u该点的波形

shangdawei

好的, 谢谢!

shangdawei

shangdawei

High Voltage to 3.3 V CMOS
Higher voltages (12 V to 18 V) typically come from outside the module. Any type of signals coming from
outside the module must have signal conditioning circuitry to limit noise spikes that can damage the
device from over current or over voltage.
Usually these circuits take the form of a voltage divider similar to the 5 V CMOS to 3.3 V CMOS case
above except that a capacitor must also be included from the device pin to ground to limit voltage
transients. Typically, test methods for automotive circuits require the inputs to survive 200 V spikes of
prescribed waveshapes.

The divider network R1/R2 is set to translate 18 V down to 3.3 V. 18 V is the maximum dc voltage that the
module expects to see from the charging system, even though 12 V is typical when the engine is off, and
cranking volts can be as low as 4 V. R1 must be set large enough to avoid exceeding the device pin’s
maximum input clamp current in the event that some rocket scientist uses double battery (24 V) to crank
the vehicle in the winter. The time constant of the parallel resistance (R1||R2) in combination with C1 is
set to absorb the 200 V spike without overstressing the input as well. It can quickly be observed that there
are more constraints than there are variables (if 4 V is a marginal "one" then 18 V will certainly forward
bias the input clamp circuit.)

shangdawei

高电压3.3 V CMOS
较高的电压（12V至18V）通常来自模块外。任何类型的信号，从未来
外的模块必须具有信号调节电路，以限制噪声尖峰，可以破坏
从设备过电流或过电压。
通常这些电路利用一个分压器类似于5伏CMOS至3.3 V的CMOS的情况下的形式
以上只是一个电容器也必须包括从设备引脚到地，以限制电压
瞬变。典型地，试验方法汽车电路所需要的输入生存200伏尖峰
规定的波形，。

分压器网络R1 / R2被设定为平移18 V下降到3.3 V18，V是最大直流电压，该
模块期望的充电系统看，即使12 V是典型当发动机处于关闭状态，并
作为4 V. R1必须设置足够大，以避免超过器件的引脚的起动电压可低至
最大输入钳位电流的情况下，一些火箭科学家采用双电池（24V）曲柄
车辆在冬季。并联电阻的时间常数（R1|| R2）结合C1是
集吸纳200 V秒杀无过分强调输入，以及。它可以迅速地观察到，有
更多的约束条件之外还有变量（如4 V是一个边际“一”，那么18 V肯定会向前
偏压输入钳位电路。）

shangdawei

3.3 V I/O Considerations for Hercules™ Safety MCUs in Automotive and Industrial Environments

liyf

芯片内部还有个esd保护的

shangdawei