【讨论】MOS驱动芯片的设计考虑
怎样根据MOS来选取合适的驱动芯片，芯片技术指标中那些与时间相关的参数到底有哪些影响，芯片内部的功耗如何计算，为什么把芯片的输入、或输出通过耦合电容、驱动变压器后波形存在了各种各样的问题，各种功率拓扑到底应该怎样设计驱动电路等.
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1。与时间相关的指标
1。1 上升与下降时间
For the Rising time tr and Falling time tf are governed by three factors. These are operating temperature, supply voltage Vdd, and output load. Since the low side gate drivers were designed to drive power MOSFETs the output load is expressed in Farads. This is due to the fact that a MOSFET gate looks like a capacitor to the driving device, which is actually appears as a variable nonlinear capacitance. The rising time, tr, is defined as the period from 10% to 90% of output rail-to-rail level to supply source Vdd, while the falling time, tf, is defined as the period from 90% to 10% of output rail-to-rail level to supply source Vdd, both on Enable active, as shown in Fig. 1.
The rising and falling time is the function of output load Cload, supply voltage Vdd, and operating temperature. Little can be done to lower the rising and falling time except for keeping the device temperature low and choosing Cload as small as possible. There are several factors associated with the rising and falling times. In general, the rising and falling times are not equal creating a small asymmetry in the output waveform. This is due to having a P-channel device source current and an N-channel sink current from the load at the output stage. P-channels do not perform as well as N types, so this does not make the P equal to the N in dynamic performance. This difference is most obvious at higher loads. Meanwhile, rising and falling times also determine the minimum pulse width in that if an input pulse has a width that is less than the sum of the rising and falling times the output can’t make a full transition.
说白了，上升与下降时间是针对输出讲的，也就是驱动输出10%-90%之间的时间延迟。
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