3A buck board test FB voltage regulation CX8825

After a simple test, the circuit function is normal. The circuit board
in Picture
1 has a default output of 5V and leads to FB (VPWM), OUT, and GND.
It can be used with the fast charging protocol chip to adjust voltage to 5V, 9V, 12V, 15V, 20V, etc.
 
First read the chip manual
specification. It is very user-friendly
. The chip has built-in H-side and L-side MOS, with CV and CC functions, synchronous voltage reduction, and wired compensation functions. Suitable for portable device charging applications, wait and
 
 
see. The basic circuit is very simple.
The constant current value can be set through an external resistor.
 
 
The output voltage setting is introduced below. The picture above
is as simple as that. The VFB point reference voltage can be found through the specification book. The reference voltage is 1V. Then the next step is to pass Through formula calculation, we can know the resistance relationship required to output 5V.
 
Let R1 be 100K and the expected output voltage is 5V, then R2=(R1*VFB)/VOUT-VFB. Substitute into the formula R2=(100*1)/5-1 to be 25K
R1=100k , R2=25k, VOUT=5V constant
 
 
current output.
From the manual, we know that the CSP reference voltage is 98mv. When the voltage at both ends of Rcsp is greater than 98mv, the overcurrent protection is triggered, thus setting the maximum output current.
From the formula, we can get the limit of 98/Rsen. For example, if we set the current value
to 2A, the calculation process is 0.0098/0.0050=1.96A
 
 
 
 
with a 2A load. Simply test
the no-load SW point waveform,
2A load waveform,
 
no-load output ripple, and
2A load ripple.