GS-R12F0252.0(2006) 查看數據表（PDF） - STMicroelectronics
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GS-R12F0252.0 Datasheet PDF : 12 Pages
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Application information
4
Application information
GS-R12F
4.1
Input voltage
The recommended maximum operating DC Input Voltage is 15V including ripple voltage.
4.2
Reference voltage
No capacitor is required for stability.
4.3
Inhibit function
The inhibit feature allows to put the device in stand-by mode.
With INH pin 1 is higher than 2.2V the device is disabled and the current consumption is
reduced to less than 100µA for Vi = 15V.
With INH pin lower than 0.8V, the device is enabled.
If the INH pin is left floating, an internal pull up ensures that the voltage at the pin reaches
the inhibit threshold and the device is disabled.
The pin can be pulled to Vi to disable the device.
4.4
Multiple units synchronization
Using more than one unit on the same circuit, it is possible to synchronize the switching
frequency, connecting all pin 12 together (see Figure 4).
The unit with higher frequency becomes the master.
4.5
Current limitation
The device has two current limit protections, pulse by pulse and frequency fold back.
The current is sensed through a resistor and if it reaches the threshold, the on time is
reduced and consequently the output voltage, too.
Since the minimum switch ON time (necessary to avoid false overcurrent signal) is not
enough to obtain a sufficiently low duty cycle at 250Hz, the output current could increase
again, in strong overcurrent or short circuit conditions.
For this reason the switching frequency is also reduced to keep the inductor current within
its maximum threshold limit.
The frequency depends on the feedback voltage.
As the feedback voltage decreases (due to the reduced duty cycle), the switching frequency
decrease too.
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