This is how to use the LM2596S-ADJ DC-DC step-down chip

fish001

This is how to use the LM2596S-ADJ DC-DC step-down chip [Copy link]

Let's start with the official schematic, which is quite detailed. The circuit is basically the same as the official one, except for the different types. The models are clearly written down by the experts, which makes it very convenient to make. I planned to make a demo board myself, so I started buying components. Damn, an original LM2596S-ADJ cost as much as 10 RMB (PS: the purchase price obtained through normal channels, agent channels and Taobao channels), while the domestic one cost 1 RMB, which made me hesitate. I only bought this board for 3 RMB. Isn't this disgusting? Then search on Baidu and consult the agents. It turns out that most of the cheap LM2596S-ADJ chips are made by erasing the LM2576 and then printing it on. If you see that the surface of the chip you bought is fuzzy and has obvious signs of polishing, congratulations, you have won the prize! Then, nothing happened. I had an idea. I was recently making a robot chassis and left a power interface for customers. Some needed 24V, some needed 19V, some needed 5V, and so on. Suddenly I thought I could use the DAC function to control the output voltage through the microcontroller pin. I tried it decisively. Here is the schematic diagram first: Calculation process: Current I3 flowing through resistor R3, current I2 flowing through resistor R2, current I1 flowing through resistor R1 FB pin feedback voltage VFB, microcontroller DAC output voltage VG, diode voltage drop VD, Through the following deduction: I3=(VG-VD-VFB)/R3 I2=(VOUT-VFB)/R2 I1=VFB/R1 VD is the diode conduction voltage 0.4V VFB=1.23 (VG-1.23-0.4)/R3+(VOUT-1.23 )/R2=1.23/R1 (VG-1.63)/R3+(VOUT-1.23)/R2=1.23/R1 When VG<=1.63V, I3=0,VOUT=1.23*(1+R2/R1)=23.78V When VG>1.63V, VOUT=1.23*(1+R2/R1)-(VG-1.63)*R2/R3 When VG=3.25V, the minimum output VOUT=23.78-35.64/R3=23.78-23.78=0V So it can be adjusted from 0-23.78V