DC Power Supply Board V2.0

This topic describes version 2.0 of the Tuya Sandwich DC power supply board.

Background Information

The Tuya Sandwich DC power supply board is part of the Tuya Sandwich Development Kit and is used to power other related components of Tuya Sandwich.

The power development board has two input ports: DC 12V and DC 5V.

• When DC 12V is input, two SY8012B chips work at the same time, which can provide DC 12V, DC 5V, and DC 3.3V power supply for other development board components.
• When DC 5V is input, only one SY8012B chip works, which can provide DC 5V and DC 3.3V power supply for other development board components.
• Support lithium battery power supply, which can output DC 5V and DC 3.3V power supply.

Features

The Tuya Sandwich DC power supply board adopts the standard Arduino dimensions. You can directly stack the development boards on top for power supply.

• Flexible input: There are DC 005 DC 12V input, micro USB DC 5V input, and rechargeable 3.7V 15400 packaged lithium battery input.
• Overvoltage protection: with 12V TVS tube and 5V TVS tube.
• Anti-reverse connection circuit: 12V input terminal has an anti-reverse connection protection circuit composed of fuse resistor and TVS tube.
• Anti-current backflow: SS14 prevents current backflow during 5V power supply.
• Buck circuit: Choose Silicon Lijie SY8012B chip, with 5V 1A, 3.3V 1A power supply capability, and adopt SOT23-6 package.
• Indicator lights: 12V, 5V, and 3.3V power outputs have corresponding indicators, as well as lithium battery charging indicators.

Key components

Tuya Sandwich DC power supply board hardware includes 12V to 5V DC-DC step-down chip, 5V to 3.3V DC-DC step-down chip, micro USB port, 12V DC input port, lithium battery charge and discharge chip, and USB 5V output port. As shown in the following table:

I/O port

The peripheral interface configuration of the development board is shown in the figure below.

• 1: Micro USB input port, input voltage range: 4.5V to 5.5V.
• 2: DC005 input port, input voltage range: 7V to 12.5V.
• 3: USB AF output port, output voltage range: 4.5V to 5.5V.
• 4: Lithium battery access port. Only rechargeable 3.7V 15400 packaged lithium battery can be used.

The pin definition is as follows:

Technical requirements of power supply

• Power input supply voltage is 12V or 5V, and 12V and 5V cannot be supplied at the same time.

• The power board outputs a rated power of 5W.

• Refer to 12V power adapter for 12V power supply capacity.

• The maximum output current of 5V power supply is 1A.

• The maximum output current of 3.3V power supply is 1A.

• The maximum output current of USB AF is 1A.

  Note: The power board cannot output 5V/1A and 3.3V/1A at the same time.

Schematic diagram and PCB

• The schematic diagram of Tuya Sandwich DC power supply board is as follows:
  

• The PCB of Tuya Sandwich DC power supply board is shown in the figure below:
  
  

Things to note

• When using micro USB 5V or USB AF for power supply, pay attention to the fact that the holder is easily damaged when excessive force is applied.
• The power supply is 5V and 3.3V with a rated output current of 1A. When the load is too large, the output voltage will be lowered.
• Pay attention to the polarity of the input voltage when powering the 5V input external wiring, in order to prevent damage to the power supply board in case of reverse connection.
• Lithium battery can only choose rechargeable 3.7V 15400 packaged lithium battery. It cannot be replaced with an AA dry battery. The voltage range of lithium batteries can only be 3.7V to 4.2V.

Reference

• Demo Center
• Sandwich Development Kit