SX1308 boost module voltage regulation
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SX1308 chip
The SX1308 chip is a fixed-frequency boost chip, which is packaged in SOT23-6. The specific detailed parameters can be seen in the SX1308 chip manual. Here we mainly look at the recommended circuits and pins of the chip manual.
Chip recommended circuit
Chip pin description
| Pin | name | Features |
|---|---|---|
| 1 | SW | Switch node, connected to the inductor |
| 2 | GND | Ground |
| 3 | FB | Output feedback pin (feedback voltage 0.6V) |
| 4 | IN | Enable pin. When driving EN is greater than 1.5V, it activates work, and when it is less than 0.4V, it turns off work. Don't leave EN pin floating. |
| 5 | IN | The input power supply pin must be placed close to the input ceramic capacitor |
| 6 | NC | Vacant feet |
circuit analysis
Seeing the recommended circuit above and reading the chip manual, you can find that the output voltage of the chip itself is determined by the feedback voltage divider resistors R1 and R2, and the output voltage is calculated by the formula Vout=(1+R1/R2)
then now we Adjust the value of resistor R1 to change the output voltage. Just change R1 to a potentiometer. This is the blue precision potentiometer on the module above.
In theory, we only need to turn the potentiometer to change The resistance value can directly adjust the voltage
Voltage regulation
The three different modules at the top of the article work basically the same way of remote adjustment. The module adjusts the voltage by turning the potentiometer, but here the factory potentiometer is in the safe range of the module and cannot be adjusted. After leaving the factory, the voltage needs to be measured and rotated counterclockwise ( It may be 20 laps or 15 laps.), it can be adjusted normally after the output voltage measured on the multimeter changes, as shown in the figure below.
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Generally, this adjustment is fine, but there may be cases where the voltage does not change after turning counterclockwise. Don’t worry, we follow the steps below.
Adjustment method when counterclockwise is invalid
The multimeter measures the resistance of the two pins of the module in the figure below. If the resistance is not 0 (close to or basically 0), then turn the potentiometer counterclockwise to the above steps until the voltage is adjustable, or the resistance is 0, in the middle When screwing, if the voltage changes, it will enter the adjustable range and you can use it directly.
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At this time, if the measured resistance is 0, then we will supply a 5V voltage to the module and continue to turn the potentiometer, but turn it clockwise (refer to the figure below for the direction of rotation) until the voltage changes and enter the adjustable range, then Just use it normally and screw it to the voltage you need
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Precautions
When turning the potentiometer, do not turn it counterclockwise for 20 turns. If it is useless, turn it clockwise for 30 turns and then turn it back and forth. It is difficult to adjust if you turn it irregularly
Don’t connect to high voltage when power is on, it is easy to burn, try to use 5V power supply to adjust (12V or higher, it is easy to burn when power on), 5V power supply is also easier to find
to sum up
The problem of adjusting the voltage is more likely to occur because it is still invalid after 20 turns counterclockwise. It is not sure if you want to turn it counterclockwise. If the reference voltage cannot be adjusted, you can
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