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LP38693: LP38693MPX-1.8/NOPB

Meria Jacob
Intellectual 370 points
Part Number: LP38693

Hi,

I am planning to use LP38693MPX-1.8/NOPB to generate 1.8V from  3.3V. Could you please share the design  for the same?

Thanks,

Regards,

Meria Jacob

  • 0
    Intellectual 370 points
    Hi, Kindly confirm if the below circuit will work
  • 0
    Intellectual 370 points
    Hi, Kindly confirm if the above circuit will work, to generate 1.8V from 3.3V.

    Please let me know if any modifications to be done. Also confirm on the part number LP38693MPX-1.8/NOPB
  • 0 in reply to Meria Jacob
    TI__Genius 13850 points

    Hi Meria,

    Your circuit looks good. One thing what I see is input and output capacitors capacitance value. I see you have specified them to be 16V tolerating 1uF capacitors so capacitance derating due to dc voltage bias will be quite small but temperature also affects. So recommended is to use good temperature coefficient capacitors (temperature types Z5U, Y5V or X7R/X5R) or increasing value to 2.2uF.

    Best regards,

    Jari Niemelä

  • 0 in reply to Jari Niemela13
    Intellectual 370 points

    Hi,

    We are using the following capacitor for C2 and  C4

    CC0603KRX5R7BB105 CAP CER, 1UF, 16V, X5R, 10%, 0603 YAGEO

    For C3 we are using 

    C0402C104K4RACTU CAP CER 0.1UF 16V 10% X7R 0402 KEMET

    Could you please confirm if the part number LP38693MPX-1.8/NOPB and the value of R45 is correct?

    ERJ2RKF4703X 470 Kohm, 100 mW, ± 1%, 50 V Panasonic

    Thanks,

    Regards,

    Meria Jacob 

  • 0 in reply to Meria Jacob
    TI__Genius 13850 points

    Hi,


    Per datasheet capacitors are as recommended. LP38693MPX-1.8/NOPB is SOT-223 package version. R45 value is quite high it could be a lower value also since EN pin has high input resistance itself. If EN pin is not needed it should be tied straight to the VIN voltage ( actually datasheet claims straight connection to the VIN if EN functionality is not needed).

    Best regards,

    Jari Niemelä

  • 0 in reply to Jari Niemela13
    Intellectual 370 points
    Thanks for the reply.
    May I know if the 470K at the EN will cause any issue to the performance pf the LDO. Meanwhile I am also checking with the layout, if its possible to remove it and directly short the EN to VIN.

    Thanks,
    Regards,
    Meria Jacob
  • 0 in reply to Meria Jacob
    TI__Genius 13850 points
    Hi Meria,

    As mentioned earlier EN pin itself is highly resistive so connecting external big value resistor makes node very high impedance and high impedance nodes are more susceptible to pick up noise from systems nearby.
    It should not cause any performance issues but just to follow the datasheet 470k resistor is quite big value and if you want to keep this resistor just for in the future needs I would populate it with 0 ohm resistor. So to avoid any issues in any case datasheet claims EN pin to have strong connection to turn on and off.

    Best regards,
    Jari Niemelä