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LM317: Could you tell me about the numbers of LM317's external parts?

Pokkun
Genius 4695 points
Part Number: LM317

Hi, team.

My customer is considering power supply with the following specifications.

Input Voltage: 20 V

Output Voltage: 15 V

Output Current: ~ 0.5 A

Target: About $0.18

My customer don't want to attach external parts as as possible.

I am planning to promotion the LM317,Looking at the data sheet, there is a fear that there will be more external parts.

＜Question＞

When that consider a circuit that merely generates the voltage of the above specifications,is the minimum necessary external parts only the under parts?

· Input capacitor

· Output capacitor

· Two FB resistors

Best regards,

Masumi Sekiguchi

  • 0
    TI__Expert 7035 points
    Hi Masumi,

    For this part the output capacitor is optional; however, it is recommended for optimal performance of the device. The input capacitor is highly recommended if the part is placed far away from the supply to the LDO. If you choose not to use an output capacitor you may want to place an additional 0.1uF bypass capacitor at the input of the LDO to add additional filtering to the input supply. The two feedback resistors will be required to set the output voltage.

    Section 8.2.2 talks about how to set the output voltage using the two FB resistors.

    Best Regards,
    Mark