LP3965: Precautions in circuit design 　LP3965

user6544808

Part Number: LP3965

I'm Wakamatsu, Second Engineering Department, Sanwa Electronics Co., Ltd. Can you give me some advice on the following events? ・ Event The output voltage is about 2.75V in the circuit of the document. When pins 4-5 are short-circuited, the output voltage becomes 2.85V. The output voltage is used for FPGA power supply, pull-up, etc. The load on LP3965ES-3.3 / NOPB is about 700Ω (1) If it is mounted on the product board and connected to the circuit in the subsequent stage, the output will be 2.75V. (2) LP3965ES-3.3 / NOPB power supply circuit only (similar circuit made on universal board) It has been confirmed that 3.3V is output when tested with. * The LP3965ES-3.3 / NOPB used at this time is the same as ① and ②. We believe that it is not a defect in the parts but a defect in the circuit. Since the cause is unknown, I wonder if there is a similar event and can you give me some advice? I made an inquiry to the manufacturer.

over 4 years ago

0 Jason Song over 4 years ago

TI__Mastermind 23361 points

Hi Wakamatsu-san,

Will you repost your pictures using the toolbox by clicking "insert/Edit media"?

Regards,
Jason Song

0 user6544808 over 4 years ago in reply to Jason Song

Prodigy 80 points

Hi,Mr.Jason Song

I sent the materials. Verification please.

From Junya Wakamatsu

資料_20210128.xlsx

0 Jason Song over 4 years ago in reply to user6544808

TI__Mastermind 23361 points

Hi Wakamatsu-san,

Will you help to capture a scope-shot with Vin, Vout? I would like to make sure Vin for the LDO is stable in the test.

Regards,

Jason Song

0 user6544808 over 4 years ago in reply to Jason Song

Prodigy 80 points

Hello, Mr.Jason Song

Sorry for the late reply. Currently, the device is not ready to boot and cannot send a voltage capture. Please wait for a while.

From Junya Wakamatsu

0 Jason Song over 4 years ago in reply to user6544808

TI__Mastermind 23361 points

Thanks for the update. Please post back when the data becomes available.

0 user6544808 over 4 years ago in reply to Jason Song

Prodigy 80 points

Hello, Mr.Jason Song

Sorry for the late reply.

We will send you the waveform image of the input / output voltage of LP3965.

Please check.

0 user6544808 over 4 years ago in reply to user6544808

Prodigy 80 points

0 user6544808 over 4 years ago in reply to user6544808

Prodigy 80 points

I'm sorry that the email was split.

The yellow line is the output voltage and the pink line is the input voltage.

From Junya Wakamatsu

0 Jason Song over 4 years ago in reply to user6544808

TI__Mastermind 23361 points

Hi Wakamatsu-san,

Thanks for providing the scope-shoots, and I was hoping you could capture the scope shoot when the pin 4 is shorting to pin 5 and shows how the output voltage changes.

When you short pin 4 to pin 5, depending how the short happens and where the measurement is taken, the result could vary.

For example, if the output is shorting to the SENSE through some kind of resistance as the following:

OUTPUT Pin--> R1--> Short --> R2-->SENSE Pin

If the measurement is taken right at the voltage pin, depending on the R1 resistance, the actual measured output could be higher. Does it make sense to you? Do you think you could have some resistance between the output pin and the sense pin when you test the shorts?

Regards,
Jason Song

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LP3965: Precautions in circuit design 　LP3965

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LP3965: Precautions in circuit design LP3965

LP3965: Precautions in circuit design 　LP3965