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LM337: LM337KTTR

Ann Gao
Prodigy 10 points
Part Number: LM337

Hello,
Glad to contact you,

 

For Linear Voltage Regulator LM337KTTR, we use it in below condition:
Vin= -5V,
Vout = -3.3V,
R1=120R, R2=196R, all the cap value follows recommended circuit.
do you have some data to tell the output current? 

The maximum loading current required is around 50mA, and we are looking forward to getting some evidence showing the output voltage is stable from your side.
Thanks and best regards.

  • 0
    TI__Expert 5060 points

    Hey Ann,

    I would like to verify that your Cin=1uF solid tantalum capacitor, and your Cout=1uF solid tantalum capacitor as well? Or are they a different value and material?

    The output current is dependent on the output load. Since LM337KTTR can handle up to 1.5A, your required load current will be within the specs of this LDO. 

    Please provide the capacitor data so I can look into getting output stability data for this LDO.

    Regards,

    Andres

  • 0 in reply to Andres Sagredo
    Prodigy 10 points

    Hi Andres，

     

    Thanks a lot for your feedback,

    Here is the application circuit, and for Vin cap and Vout caps ,we all use ceramic capacitor.

    GRM21BR61E106KA73L

    Datasheet link: GRM21BR61E106KA73_01A-1714905.pdf (mouser.cn)


    0.1UF:

    GRM033C71C104KE14D

    Datasheet link: GRM033C71C104KE14_01A-1981726.pdf (mouser.cn)

     

    My concern is Vin-Vout=-1.7V, not within recommended range, would it impact generating stable -3.3v with the condition of Iload= 50mA?

     

    Besides, I have found Pspice module on TI website for LM337-N, but not specified for LM337KTTR.

    Could you help provide Pspice module for LM337KTTR?

     

    Thank you and best regards!

    Ann Gao (高子安)

  • 0 in reply to Ann Gao
    TI__Expert 5060 points

    Hey Ann,

    For the capacitors do note the recommendations in my previous comment, this is for output stability. Also, regarding Vin-Vout, this does depend on the load current, the recommended value mentioned in the datasheet is calculated when Iout=1.5A.

    Please see this graph for LM337-N regarding dropout at different temperatures and load currents. Note that LM337-N has similar functionality to LM337.

    By looking at the 20mA curve, you can see that at 25C your dropout is slightly above 1.5V. It seems that in your application your input to output voltage difference should not put your device in dropout. However, for a stable output do look at the recommended non-ceramic capacitors mentioned in the datasheet.

    Also, since LM337-N has similar functionality to LM337, the Pspice model should be a close enough approximation.

    Regards,

    Andres