LP3961 3.3V Output wrong

tom hofacker

Prodigy 60 points

Other Parts Discussed in Thread: LP3961

Hello
i used the LP3961 LDO to adjust my voltage from a lipo battery to the desired 3.3V.

The problem is:
If I connect everything as shown in the datasheet, I get an output voltage of 3.6V.

If I connect the ERROR input over a 10k Ohm to Vout (like in the datasheet) I get this 3.6V

If I connect the ERROR input to Vin via the 10kohm I get 3.1-3.4V.

An adjustment of the signal is not possible, I also used the right capacitors with the corresponding ESR values.

Is this error known ? or does someone have an idea

Translated with www.DeepL.com/Translator (free version)

Datasheet: www.ti.com/.../snvs056j.pdf

over 4 years ago

0 tom hofacker over 4 years ago

Prodigy 60 points

Maybe the LDO is broken ?

0 Nick Butts over 4 years ago

TI__Mastermind 47175 points

Hi Tom,

Do you have a schematic you can share?

Best regards,

Nick

0 tom hofacker over 4 years ago in reply to Nick Butts

Prodigy 60 points

it is very simple, i connected the ldo with the pull up resistors and the tantalum capacitors exactly like in the data sheet. nevertheless the output voltage is wrong. The TI support tells me that the 3691 can't deliver a fixed putput voltage, but that's what the datasheet says, isn't it ? and what would you want with a non-linear ldo ?

0 Nick Butts over 4 years ago in reply to tom hofacker

TI__Mastermind 47175 points

Hi Tom,

This is not an issue that you should be seeing. The datasheet says to use a pull-up resistor for ERROR in the range 100k to 1M but you are using 10k. Have you tried a resistor in the correct range?

tom hofacker said:
The TI support tells me that the 3691 can't deliver a fixed putput voltage, but that's what the datasheet says, isn't it ?

The LP3961 is a fixed-output-only device.

Regards,

Nick

0 tom hofacker over 4 years ago in reply to Nick Butts

Prodigy 60 points

Where did you find dis information?

my datasheets sais 10k.

Tank for the help

0 Nick Butts over 4 years ago in reply to tom hofacker

TI__Mastermind 47175 points

Hello,

In the description for ERROR:

It looks like there is contradictory information in the datasheet. Please try using a pull-up resistor in the range 100k to 1M and let me know if that solves the issue. The accuracy of the output is +/-1.5%, so you should not see more than 3.3495V at the output.

Regards,

Nick

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LP3961 3.3V Output wrong