High-power DC step-down charger based on single-channel SW3538S + dual-channel SW3526

This is actually an old design from before the Spring Festival this year. After several board modifications, it's only now being released. At the time, I saw that the SW3538 had multiple protocols, high power, and a 20V 7A level, which was better than the commonly available 3518; it was also better than the competing Ingenic IP6557, the latter's high voltage 28V 5A 140W was almost unusable. Since most online designs were single-channel miniaturized modules, I planned to design it from scratch, using the schematic and the SW3526 to create a multi-output system for charging both phones and computers. My version is relatively low-cost; the 8*10CM size board can be made for free, and the chips, sockets, and inductors were all bought on Taobao. The resistors and capacitors are salvaged from other parts, and the cost per unit is estimated to be around twenty yuan.
There are currently two versions, mainly differing in the switch design. The older version, V2.1, was completed in January 2024, using N-MOS for the low-end switch. The materials are relatively easy to find, and the cost and heat generation are lower, but I always felt the negative turn-off wasn't ideal. The new version V2.3 was completed in September of this year. It uses P-MOS for high-end switching, shutting off the positive terminal, adds heat dissipation vias and double-sided overcurrent protection, and places all I2C interfaces side-by-side, with signal lines routed along the PCB surface as much as possible, resulting in a more rational design. There were issues with uploading; the V2.3 project file and Gerber are attached. This is
a DC-DC pure buck charging module based on Zhirong's car charger chip, featuring a single SW3538 + dual SW3526 design, with DC5525 and XT60 dual-interface inputs. Theoretically, it can run at a maximum of 140+65+65=270W. It has a 1A3C design; the A and C1 ports share the 3538 control, while the C2 and C3 ports are independently controlled by the 3526.
The PCB area is relatively large, and the layout may be somewhat abstract, but the single-sided component layout allows for sparse component placement, easy soldering, and good heat dissipation, facilitating the attachment of heat sinks or a casing on the back. I was lazy and didn't make a casing; four M2 nylon plastic posts for fixing are also acceptable.
Features: The layout is inspired by smart car motherboards. The input interface features a dedicated TO-252 packaged N-channel MOSFET for reverse connection protection and switching, resolving arcing issues upon power-up. R1 and C1 can be left unsoldered. For the 3538 circuit with higher power, a 1770 package inductor is used, while the 3526 uses a 1265 package to minimize inductor heat generation.
Compatibility: The SW3538 pinout is compatible with the SW3518, allowing direct replacement by removing the 5.1K pull-up resistor R9 (tested and confirmed to have no impact).
C1 port protocol: The fast charging protocol of the Zhirong single-chip solution is relatively complete. C2 and C3 port protocols:
The components already soldered in this diagram are surface-mount; the rest are through-hole components. Close-up of the three inductors: 1770 package inductors cost 3.5 yuan each, and 1265 package inductors cost less than 1 yuan each.
The sample I have is being tested. The SW3538 uses an AON6144 switch, the output path switch uses an SI7686DP, and the main input reverse connection protection switch is an FQD60N06. The MOSFET junction capacitance is relatively large; at 200W output, the highest temperature is around 50-60 degrees Celsius.
Output stability: Due to the numerous output capacitors, the solid-state + electrolytic + ceramic capacitor filtering effectively reduces the 20V output ripple to below 30mV.
Power testing: The power output is normal according to the USB meter. The highest continuous output at port C1 was tested at around 120W without problems; higher power outputs could not be tested. With a 24V input, the highest measured power of the entire unit was 200W, with an input current exceeding 8.3A. At this point, using a DC5525 input with 18AWG wire resulted in significant heat generation.
It is recommended to switch to an XT60 input for power exceeding 120W, using 14 or 16AWG multi-core copper wire. (Due to equipment limitations, the computer can only reach a maximum input power of around 120W.) Hardware bug: The fast charging indicator light on the 3538 chip is faulty; the FLED interface cannot be pulled low, causing it to remain off. I've tried two chips with the same issue, so I'm not bothering with it; it doesn't affect usage. The fast charging indicator light on the SW3526 works fine.
Software additional provisions: All three chips have I2C interfaces for connecting a microcontroller to display voltage and current, but I haven't tested it yet. I was a bit lazy with the power supply; I haven't implemented 5V or 3.3V regulation yet. Later, someone can try connecting it to an STM32 or similar microcontroller to see if it works.