Detailed explanation of the working principle of the L7908CV-DG low-dropout linear regulator

Working principle of L7908CV-DG low-dropout linear regulator

The L7908CV-DG is a low-dropout linear regulator (LDO) produced by STMicroelectronics that is characterized by high accuracy, high efficiency and low noise. The working principle and main characteristics of this product will be described in detail below.

working principle

LDO is a buck converter where the output voltage is always lower than the input voltage. There is the minimum voltage difference between the input voltage and the output voltage that allows the LDO to operate. This value is called the differential voltage. The working principle of LDO can be divided into the following steps:

1. Input voltage: The voltage range that can be input to the input terminal of the LDO requires a derating of 80%.

2. Output voltage: The output voltage value at the output terminal. Avoid selecting a regulator with ADJ function to reduce interference.

3. Output current: The maximum output current value at the output end, leaving a 25% margin.

4. Differential pressure: Determine whether the differential pressure is appropriate and check the specification for the minimum differential pressure requirement corresponding to the maximum current.

5. Packaging: Requirements for packaging form of single board PCB, structural size and production line.

6. Linear regulation rate: The impact of the regulator's input change on the output, that is, the ratio of the output voltage change to the input voltage change under a certain load. The smaller the linear adjustment rate, the better.

7. Load regulation ratio: refers to the change in output voltage under a given load change, where the load change is usually from no load to full load. The smaller the load adjustment ratio, the better.

main parameters

1. Input and output dropout voltage: The input voltage of the LDO is higher than the output voltage, but the voltage difference is generally small, and the input current is almost equal to the output current. Therefore, the larger the voltage difference, the lower the efficiency.

2. Quiescent current: The current consumed by the LDO when it does not provide load current increases as the temperature increases.

3. Ground pin current: The current flowing directly from the input terminal back to the power supply through the ground terminal, affected by the input voltage and load current.

application scenarios

LDOs are useful in some specific application scenarios, such as:

1. Low-power design: LDO can provide low power consumption and high efficiency regulated output, making it ideal for low-power designs.

2. Compact space design: LDO is packaged in a very compact form and can be used in a very small space.

3. Low-noise design: The output voltage of the LDO is very stable and the noise is very low, making it very suitable for application scenarios that require low noise.

conclusion

The L7908CV-DG is a high-precision, high-efficiency and low-noise low-dropout linear regulator suitable for a variety of application scenarios, especially low-power design, compact space design and low-noise design. Understanding the working principle and main characteristics of this product can help you better select and apply this product.

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