Taken from Masta Microelectronics：Instructions for using OE ST

Oct 21,2024
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introduction:

Have you noticed that the device has a special pin when we use active oscillators? Usually, this pin is positioned as pin 1 by the manufacturer and is assigned the function of enabling (OE) or standby (/ST). What is the difference between the two functions? Let's explore their differences in detail below.

1. Output Enable (OE) and Standby (/ST) functions of the oscillator:

Both Output Enable (OE) and Standby (/ST) control functions are switches that control the frequency output of the oscillator as a whole. It may seem like there is no difference, but there are significant differences in control principles and parameter effects.

Figure 1. Test circuit

The control logic of OE and ST is the same: that is, the frequency output is effective when the high level (H) is high; When the low level (L) is reached, the frequency output is turned off.

The CLK output terminal is generally in a high impedance state (Hi-Z) when there is no output.

Figure 2. Control Logic

Note: The effective level of OE/ST is determined according to the specifications of different products.

2. Difference between Output Enable and Standby

The function of this pin is optional, how to choose it? Let's take a look at the differences between them next.

a. If the OE function is selected, when OE=L, the internal components of the oscillator will not stop oscillating, only the output inside the oscillator will be turned off

Circuit (output end changes to HI-Z). The input current of the oscillator is basically the same as the normal operating current. When OE=H, the output terminal will quickly recover the frequency output (<1us).

b. If the/ST function is selected, when/ST=L, the oscillator enters standby mode, all circuits in the device stop working, and the overall current is maintained at standby level, which may only be a few uA or lower. When/ST=H, the oscillator requires a 'recovery' The normal output can only be achieved after a certain amount of time, which may take a few milliseconds.

The following table summarizes the differences between OE and/ST:

正常频率输出情况功耗	正常功耗	正常功耗
控制频率输出关闭	约等于正常功耗	极低功耗（待机状态）
频率输出恢复时间	极短（快速恢复）	较长（根据器件起振时间）

3. Summary:

OE and/ST functions have differences and need to be confirmed based on different usage requirements.

If the system needs to quickly activate and respond after shutdown, then select the OE function. If the system has strict requirements for power consumption, then ST function becomes the first choice, and extremely low power consumption can extend the battery life.

Finally, if this function is not required, the pin should be pulled up to a high level to ensure normal frequency output, or its function should be defined as' NC '.