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Hello everyone, today we are going to understand the PWM output voltage and current detection

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First of all, this PWM chip has an OUT pin inside

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It's not an output pin, it's a voltage input pin,

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and we call it a voltage detection input pin

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It is different from OUT in the LDO power supply mode

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In the LDO power supply mode, VOUT means output

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But the OUT, VOUT or VO pin in the PWM circuit is the voltage detection input pin,

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which is used to detect whether the voltage output at the back end of the inductor is overvoltage or undervoltage

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We often see OVP and UVP in the data books

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OVP stands for overvoltage protection, O is over, V is voltage, and P is protection

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UVP stands for undervoltage protection

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It is usually 115% above its set voltage, which is considered overvoltage,

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and below 70%, which is considered undervoltage

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Next, let's look at the current detection method

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There are two current detection methods

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The first is to connect a milliohm resistor at the back of the inductor

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The chip has CSP and CSN pins, where CS stands for current sense, P is positive, N is negative

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The CSP and CSN pins are the positive-end and negative-end input pins for current detection,

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which are connected to the output at the back of the inductor

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The voltage at the output of the inductor needs to flow through the resistor to the back stage

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If the rear stage is short-circuited or overcurrent,

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the current flowing through this resistor is enormous

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The chip calculates the current flowing through a resistor

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by detecting the voltage difference between the front and rear ends

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Therefore, there is a calculation formula: (CSP-CSN)/R=I,

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which is used to calculate the output current

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This is a very common current detection method,

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which is used by the charging chip to detect the charging current

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The second way is to judge its output current by detecting the voltage difference between the phase pin and GND

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This detection method is to detect the current flowing through the MOS tube

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when the current tube is conductive to the inductor to form the discharge loop

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The MOS tube has an internal resistance of about 10 milliohm in the state of conduction

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When the current pipe is on,

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the phase pin and PGND pin will detect the voltage difference between the D pole

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and the S pole of the lower pipe to determine the output current

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Okay, this is the second method of detection

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This is the PWM output voltage, current detection