USB 3.1 gen2 1-to-4 expansion based on VL822

STLinkV2.J28.M18_Firmware.zip

PDF_STlink V2-1.zip

Altium_STlink V2-1.zip

PADS_STlink V2-1.zip

BOM_STlink V2-1.xlsx

92398

[Verified] BQ24640 - Supports 10A current step-down supercapacitor charger

The BQ24640-based step-down synchronous rectifier supercapacitor charger supports charging currents up to 10A, 5-28V input, and 2.1-28V output; with extremely low ripple, referencing the official EVM layout.

Introduction:
        The BQ24640 is a 600kHz switching frequency, NMOS-NMOS synchronous buck topology supercapacitor charging controller. It supports 5-28V input voltage and 2.1-26V output voltage. It features CC-CV mode switching, supports 0V start-up charging for supercapacitors and other devices, supports charging currents up to 10A while maintaining efficiency above 90%, and supports high-temperature capacitor protection. In sleep mode, when the input voltage is removed, the capacitor current drops to as low as 15uA, reducing energy consumption.
 
Key Components/Replica Considerations:
1. I used the APG068N04G MOSFET, which costs about 60 cents each on Taobao. It has a 40V withstand voltage, an on-resistance of less than 6.8mΩ at 10Vgs, and a Ciss of 840pF. In actual testing, the on-resistance seemed a bit high, but the BQ24640 drove it reasonably well. A MOSFET with a larger Ciss could probably be used instead.
2. The surface-mount power inductor is a common 1770 package molded shielded surface-mount inductor found on Taobao, with a capacity of 6.8uH. While slightly bulky, its measured temperature rise at 9.5A is not high. In practical applications, if size is a concern, a smaller package can be used, and the inductance value can be appropriately reduced (e.g., using 4.7uH or 3.3uH) if ripple requirements are not high.
3. For 10A applications, the official recommendation is to use at least two 47uF capacitors in parallel at the input and output. The capacitor connected in series with a resistor acts as an RC filter to prevent high-voltage spikes from generated by the parasitic inductance of the circuit during power supply, which could damage the MOSFET and the main control IC. In the RC filter for the main control I2C power supply, the value of R should not be too large; the official recommendation is 4.7-30 ohms, and the package should be 0805 or 1206.
4. For the current sampling resistor, attention needs to be paid to power rating and temperature drift. Actual testing showed that for a 10A application, a 5mΩ, 2512 packaged current sampling resistor exhibits a significant temperature rise (reaching 60-70°C) at room temperature (23°C). This may cause malfunction when the current approaches the set overcurrent protection current; caution is advised.
5. For the MOSFET drive circuit, fast recovery diodes should be used. For this layout, a 2-ohm gate drive resistor is sufficient to obtain a good gate drive waveform. Other layouts require actual testing and adjustments.
Measured Data:
All test conditions for the following data are:
1. Room temperature 23°C
2. 12V to 5.2V, electronic load constant current mode
3. Test instruments:
Oscilloscope: Hantek DSO2C15
Power supply: ETM3010P
Electronic load: DCL8003+
Thermal imager: IRay C210
Due to limited personal time and expertise, it is impossible to control too many variables; therefore, this data is for reference only.
1. MOSFET gate drive waveform:
High-side MOSFET (to ground)
Low-side MOSFET (to ground)
(Since the waveforms remain basically unchanged across power ranges, only one set is tested.)
The following are constant current tests, showing the input and output voltages respectively. Some include thermal images after temperature stabilization.
1A load constant current test:
Input:
Output:
(These are indeed the values; it's not due to poor contact or something not being measured, because if there were poor contact and it wasn't measured, the induced noise would be much greater.)
 
3A load:
Input: Output
:
 
5A load: Input:
Output
:
 
7A load:
Input:
Output:
 
8A load:
Input:
Output:
 
9A load:
Output:
 
9.5A load: Input
: Output
:
 
Long-term temperature rise:
Under a 9A load for 30 minutes, the upper transistor
experienced the largest temperature rise: The upper transistor reached approximately 90 degrees Celsius, and the lower
transistor reached approximately 77 degrees Celsius. The current sampling resistor also had a significant temperature, nearly 80 degrees Celsius. At 9.5A, the temperature drift of the sampling resistor increased further, causing the main controller to misjudge overcurrent and shut down, making testing impossible. For extended use, it is recommended to
keep the current below 9A; the main controller IC remains relatively cool, at only around 61 degrees Celsius. It seems a transistor with a larger ciss and lower on-resistance could be used.
The inductor, being a metal, has a different emissivity, requiring thermocouple temperature measurement, which showed a temperature of around 65 degrees Celsius, relatively cool.
 
Another precaution:
When using constant current mode with an electronic load, if overcurrent protection is accidentally triggered, causing the IC to hiccup and start, the lower transistor and IC temperatures will rise rapidly during low-voltage output, potentially causing burnout!

PDF_[Verified] BQ24640 - Step-down Supercapacitor Charger Supporting 10A Current.zip

Altium_[Verified]BQ24640 - Step-down supercapacitor charger supporting 10A current.zip

PADS_[Verified]BQ24640 - Step-down supercapacitor charger supporting 10A current.zip

BOM_[Verified]BQ24640 - Step-down Supercapacitor Charger Supporting 10A Current.xlsx

92399

[Verified] 1.3-inch OLED (SH1106 driver, seven-wire SPI)

We found that bare OLED screens are relatively inexpensive, but modules are expensive. Therefore, we created a 1.3-inch OLED module (adapter board) to allow users to achieve OLED freedom (note that it only applies to 1.3-inch OLED screens driven by SH1106). SPI and IIC communication can be selected via R1 and R3.

The pins are compatible with commercially available seven-wire SPI OLED modules, and can be directly replaced.
The SH1106 driver is basically the same as the SSD1306, but the column start address needs to be changed to 0x02.

Updated September 7, 2024: If intermittent screen flickering, overheating, or no display occurs in this project or other designs derived from this project, first check if it is caused by poor soldering of the FPC cable. If this method is ineffective, **consider replacing all existing capacitors with capacitors with higher voltage ratings. A voltage rating of 16V or higher is recommended.**

```
/**
* ************************************************************************************************
* @brief Send buffer
* @note
* - Low column start address is 0x02 when using a 1.3-inch OLED display
* - Low start address is 0x00 when using a 0.96-inch OLED display
* ****************************************************************************************
*/
// Update video memory to OLED
void OLED_Refresh(void)
{
u8 i, n;
for (i = 0; i

PDF_【Verified】1.3-inch OLED (SH1106 driver, seven-wire SPI).zip

Altium_【Verified】1.3-inch OLED (SH1106 driver, seven-wire SPI).zip

PADS_【Verified】1.3-inch OLED (SH1106 driver, seven-wire SPI).zip

BOM_【Verified】1.3-inch OLED (SH1106 driver, seven-wire SPI).xlsx

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electronic