I Have a Technical Question regarding the UC28023 - High Speed PWM controller. I expected the specification to be found in the datasheet, but it is not.
The Soft-Start Pin (pin 8) allows me to linearly charge the capacitor (from the internal 9uA Current Source) to turn the PWM Controller on. I would like to know at what Voltage on the Soft-Start Capacitor the device starts switching the PWM, and I do not see a specc for this in the Datasheet.
Based on the Block Diagram it seems this node is connected to an Inhibit (ENABLE/DISABLE) transistor of the error amplifier. At what Voltage does this turn the switching on? In my lab-prototype I have measured this to be around 2.8V.
One can easily test this by putting the UC28023 in any functional operation, placing a large (say 50uF) capacitor on the SS pin, and monitor both the SS-pin Voltage and the PWM-Output (pin 14). I have measured that no switching occurs until the SS pin reaches around 2.8V on my particular prototype.
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