This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LM27313: Too much drop voltage with the init of the boost LM27313XMF.

Part Number: LM27313
Other Parts Discussed in Thread: TLV61046, LM2623, PGA460

Hi everyone,

I'm using the LM27313 boost converter in an application with a primary battery of 3.6V / 5000mA. I have some trouble due to a drop off voltage. The voltage drop from 3.6V to 2V. Yellow (Voltage: 1V/D) and blue(Current: 60mA/D)

Is there any way to reduce this drop voltage?

I don't know but I'm not probably using the correct part number and there is another one better. My requirements are the following...

I need to boost voltage from a primary battery of 3.6V to 7.5V with a maximum output current of 50mA, and I need that this IC starts in a soft way, in order to avoid peak currents and drop off voltage.

Is there another better alternative for this application?

Best regards.

  • The voltage drop is very big. You need to take care of the connection. You can also use TLV61046 in your application.
  • Thank you very much for your help and quick reply.

    I think that with an internal 7-ms Soft Start Time wil be goog enough.

    Best regards.
  • On question more,

    In some application I need a battery of 7.2V instead of 3.6V. Is there any part number similar to this one TLV61046 with an Input roltage range up to 8 Volts?

    Best regards.

  • Hi Oscar,
    Input source is a 3.6V battery or a 7.6V battery, and output current is 50mA. What is the output voltage?
  • Hi Jing,

    First of all, thank you very much for your help an quick reply.

    I am sorry but I made a mistake.

    I have two different products, one of them is feed with a primary lithium battery of 3.6 Volts and the other one is feed with two series 3.0V primary lithium battery, so the total nominal voltage is 6.0 Volts.

    I need a boost with an ideal Vinput range from 1.8V to 6.6V or something like that. The output boost has to be 7.2Volts.

    Best regards.
  • Hi Oscar,

      You could use LM2623.

    Vin: 0.8V~14V (1.1 V start up)

    Vout: 1.24V to 14V

    peak current limit: 1.2A(min)

  • Hi Jing,

    Yes, this one is a good option, but it doesn't have a soft start, does it?

    This is one of the resons I want to change from the device LM27313 to another one.

    Best regards.
  • Hi Oscar,
    Some boost devices have SS pin to change soft start time; Some boost devices without SS pin will has internal soft start even we don't mention it in the datasheet. So LM27313 and LM2623 both have internal soft start.
    Do you have some special requirement about soft start? Do you want to change SS time?
  • Hi Jing,

    I am activating the LM27313 using a load switch. More concretely, I'm using the part number AP2280.

    As you can see in my first message (In this case the voltage input is 3.6 Volts), I have trouble with a peak current and the input voltage drop too much and then my ucontroller do a reset.

    This is the reason I need a soft start in order to avoid this kind of peaks and drop voltage.

    Best regards.
  • Hi Oscar,

      So your problem is :

      The input of LM27313 is a 3.7V battery and when the output current is from 0mA to 150mA, the battery voltage is decrease to 2V. Is it right?

     If your phenomenon is like I said, the reason is not soft start problem. Because it happens at load transient not start up.

     You need to check

     1 For LM27313, Vin is a battery, output : E-load set Iout=150mA, steady state and test Vin? Vin =3.7 or 2V?

  • Hi Jingi,

    According to: "The input of LM27313 is a 3.7V battery and when the output current is from 0mA to 150mA, the battery voltage is decrease to 2V. Is it right?"

    Not exactly, I'm going to give you more information.

    First of all, I'm going to show you my electronic diagram:

    The LM27313 is used to feed a PGA460 which I'm using on my device.

    In order to try to understand what is happening, I've removed the AP2280, in order to reduce the number of possible sources of error.

    I made some measurements using a DC power analyzer instead of using a battery. The power Supply Analyzer was set up to give 3.6 Volts and the current limit was set up to limit to 250mA.

    In this image, you can see V1 (Yellow): BATT_MEAS and I1(Blue) the current.

    And in this image, you can see in the channel 4(Pink) 7.5V and channel 1(Yellow) BATT_MEAS:

    So I've activated the LM27313 with a pull-up (SHDN, pin 4 LM27313), and then you can see how the BATT_MEAS down (around 2 Volts) during the startup process.

    This is what I want to try to understand.

    Any suggestion?

    Best regards.

  • Hi Oscar,

      If you want to verify this input drop is because of soft start time, Could you do the following test to prove it.

      Could you set  the power Supply Analyzer's current limit to 1A? and test?

      Another idea: you could make C6 bigger like 47uH.and test?

     

  • Hi Jing,

    I did the tests.

    1. DC Power Analyzer with a limitation of 1A:

    First Graph: BATT_MEAS (Yellow) and Current (Blue).

    Second Graph: Channel 4(Pink) 7.5V and Channel 1(Yellow) BATT_MEAS:

    2. DC Power Analyzer with a limitation of 250mA but with C6 = 47uF

    First Graph: BATT_MEAS (Yellow) and Current (Blue).

    Second Graph: Channel 4(Pink) 7.5V and Channel 1(Yellow) BATT_MEAS:

    The capacitor improves a voltage drop of around 1Volts. I think it could be good enough.

    For me the best option it is the TLV61046, because the soft start of 7msec is better.

    I have to scenarios:

    1. Vinput = 3.6V. For this scenario, I can use the TLV61046.

    2. Vinput = 3V + 3V (2 primary batteries in series. Vinput = 6.4V). For this scenario,  I can probably use a linear regulator for change 6.2V to 5.5V.

    Best regards.

  • Hi Oscar,
    Do you have any more question about this? if not, could you click "This resolved my issue" button?