[经验]

请问振荡器中待机（ST）与输出允许（OE）有什么不同？

2018-10-31 07:10:04

3005 振荡器可编程

振荡器，包括可编程和引脚可配置器件，在其标准4或6引脚封装的大多数情况下，将引脚1保留为称为输出使能（OE）或启用/禁用（E / D）的功能。
（某些供应商，如Silicon Laboratories，Microchip和其他供应商都有一系列振荡器，其中OE功能可以选择为引脚1或引脚2）。
一些供应商，在同一系列或另一个部件号下，有一个称为待机（ST），掉电（PD）或抑制（INH）的引脚1。
那么，有什么区别以及何时应该使用每个选项？
在这两种情况下，当此引脚1被激活时（它可以是“1”或“0”），它会使输出时钟变为三态或Hi Z（高阻抗）;
因此，允许更少的PCB层时钟走线振荡或允许另一个时钟源馈送相同的器件或设计人员希望时钟转到Hi Z的任何其他应用情况。
输出使能和待机功能之间的主要区别在于振荡器应保持有效状态并再次驱动时钟输出（振荡）。
如果选择了输出使能（OE）功能，则元件内的振荡不会停止，只有振荡器内的输出电路关闭（振荡器输出门变为Hi Z）。
电源线上的振荡器输入电流几乎与正常工作电流相同。
如果选择了待机（ST）功能，则振荡器内的所有有效电路都将关闭。
这导致电源线上的输入电流几乎为零。
要恢复振荡，振荡器必须经历启动期。
振荡器数据手册中的供应商定义了称为“启动时间”的参数，范围为3 ms至10 ms。
这是相当长的时间（相对于使用OE选项的纳秒），并且许多性能和速度都很关键的应用程序无法容忍这种延迟。
另一方面，对于电池供电的应用，关键问题是电池寿命，因此它们可以容忍这种相对长的延迟以降低电路的总功耗。

以上来自于谷歌翻译

以下为原文

Oscillators, including programmable and pin configurable devices, in the majority of the cases in their standard 4 or 6 pins packages, reserve pin 1 to a function called Output Enable (OE) or Enable/Disable (E/D). (Some vendors like Silicon Laboratories, Microchip, and others have a series of oscillators where the OE function can be chosen to be pin 1 or pin 2.)

Some vendors, in the same series or under another part number, have this pin 1 called Standby (ST), Power Down (PD), or Inhibit (INH).
So, what is the difference and when should each option be used?
In both cases, when this pin 1 is activated (it can be either “1” or “0”), it causes an output clock to become tri-stated or Hi Z (High Impedance); thus, allowing fewer oscillations in clock traces of PCB layers or allowing another clock source to feed the same device or any other application cases where the designer will want the clock to go to Hi Z.
The main difference between Output Enable and Standby functions is when the oscillator should retain the active state and drive the clock output again (to oscillate).
If the Output Enable (OE) function is selected, oscillation inside the component is not stopped, only the output circuitry within the oscillator is shut down (the oscillator output gate becomes Hi Z). The oscillator input current on the power supply line is almost the same as normal operating current.
If the Standby (ST) function is selected, all active circuitry within the oscillator is shut down. This results in the input current on the power supply line going to almost zero.
To resume oscillation, the oscillator must go through a startup period.
The vendors in their data sheet of the oscillators define the parameter called “Start-up time” in the range of 3 ms to 10 ms. This is rather a long time (vs. nanoseconds using OE option) and many applications where the performance and speed are critical can’t tolerate this delay.
On the other hand, for battery powered applications the critical issue is a battery life, so they can tolerate this relatively long delay to decrease overall power consumption of the circuitry.