SG3525 sawtooth wave output problem

S3S4S5S6

SG3525 sawtooth wave output problem [Copy link]

 

The sawtooth wave of SG3525 is very unclean, as shown in the figure below

What are the reasons for this waveform? 1. PCB layout; 2. . .

maychang

1. The control chip's 16th pin (Vref) should have a capacitor of 0.1uF or more connected to the ground.

2. There should be a small resistor from pin 7 of the chip to pin 5.

3. The chip's 15th pin (Vcc) should have a capacitor of 0.1uF or more connected to the 12th pin (GND).

S3S4S5S6

maychang posted on 2024-9-13 15:27 1. The 16th pin (Vref) of the control chip should have a capacitor of more than 0.1uF connected to the ground. 2. The 7th pin of the chip should have a small resistor connected to the 5th pin. 3 ...

There is no capacitor on pin 16, but there are on pins 2 and 3.

maychang

S3S4S5S6 posted on 2024-9-13 16:48 There is no capacitor on pin 16, but there is on pins 2/3

Then add the capacitor on pin 16. Note that the capacitor should be as close to the chip as possible and the connection line should be as short as possible.

In addition, the rest of the board, such as the bridge circuit consisting of four low-power transistors, should be removed (cut off the power cords of the rest of the board to stop it from working).

S3S4S5S6

maychang posted on 2024-9-13 17:00 Then add the 16-pin capacitor. Note that the capacitor should be as close to the chip as possible and the connection line should be as short as possible. In addition, the rest of the board, such as the four...

Pin 10 of SG3525 is controlled by the microcontroller. When the voltage is set, this pin is high and the output of SG3525 is disabled.

After the voltage setting is completed, the voltage of pin 10 is pulled low, and the output of SG3525 is turned on.

When the output of SG3525 is disabled, the sawtooth wave is as shown below

When the output of SG3525 is enabled, the sawtooth wave is as shown below

maychang

S3S4S5S6 posted on 2024-9-13 17:21 The 10th pin of SG3525 is controlled by the microcontroller. When the voltage is set, this pin is high level, and the output of SG3525 is disabled. After the voltage setting is completed...

The waveform on the 5th floor is normal.

Since the waveform is abnormal when the SG3525 output is enabled, the signal returned from the two output terminals of the SG3525 should be considered. Cut off the wires between the two output terminals of the SG3525 and the bridge circuit composed of four transistors (leave the two output terminals floating) and try it out.

S3S4S5S6

maychang posted on 2024-9-13 17:26 The waveform on the 5th floor is normal. Since the waveform is abnormal when the SG3525 output is enabled, the signals returned from the two output terminals of the SG3525 should be considered. Put S ...

Remove R22/R23 and measure the waveform as follows: