A kind of 3G mobile video surveillance system power circuit

TI's TPS75003 and TPS62040 power management chips are selected. TPS75003 has two topological power supplies that can provide a maximum of 3 A and one 300mA LDO power supply. Each Buck output voltage range is between 1.2V and 6.5V, and the LDO output voltage range is 0.9V. to 6.5V, and the input voltage range is between 2.2V and 6.5V. TPS62040 is a high-efficiency asynchronous switching DC/DC conversion power supply with a conversion efficiency of 95%. The input voltage range is from 2.5V to 6.0V, and the output voltage is from 0.7V to 6.0V, so it can be powered by the main power supply +5V.

The system power supply is divided into four types: +5V, +3.3V, +1.8V, and +1.2V. The main power supply of the system is +5V, and the rest are supplied by the +5V power supply. Therefore, a TPS75003 and a TPS62040 are used to complete the conversion of the four power supplies of the system. The SW1 pin of the TPS75003 is designed to output a 1.2V voltage after SI2323 freewheel shaping for the DM6446 core power supply. The IS1 pin is connected to the reference voltage, the FB1 pin is connected to the output 1.2V voltage as feedback, and the SW2 pin outputs a 3.3V voltage for DM6446 peripheral interface power supply. After the SW1 and SW2 pins of TPS62040 are short-circuited, the output voltage is 1.8V for the DM6446 memory interface power supply, and the FB pin is connected to 1.8V as a feedback input. In this way, a TPS75003 and TPS62040 power management chip can satisfy the power supply of this system. The TPS75003 and TPS62040 power conversion circuits are shown in Figure 1.