• State Resolved
  • Locked Locked
  • Replies 8 replies
  • Subscribers 65 subscribers
  • Views 1114 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

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.

LMR14006YEVM

Jordda
Intellectual 665 points
Other Parts Discussed in Thread: LMR14006, LMR14006YEVM, LM2842, LMR23610

I have bought LMR14006YEVM and check its datasheet. It says the input voltage range is from 6 to 18V. But I found LMR14006 specification says it can support 4~40V. So my question is .....


The max output current in our product is below 100mA. Can I have 40V input to LMR14006YEVM to get 5V ?

Thanks for advice.

  • 0
    TI__Genius 10095 points

    Hi,

    The LMR 14006Y has a minimum on-time of 95ns.  This means that the part will not be able to support a fixed switching frequency of 2.1Mhz at a duty cycle less than .1995.  40 Volts to 5V is a duty cycle of 5/40 =0.125.  Below this duty cycle the part will skip cycles to remain in regulation.

    I would recommend swapping the LMR14006Y for a LMR14006X which runs at 1.1MHz. The lower switching frequency means that it can support a duty cycle of 0.1045 and still maintain a fixed switching frequency.

    Regards,

    Marc

     

     

  • 0 in reply to Marc Davis-Marsh
    TI__Prodigy 80 points

    Hi,

    Agree with what Marc said. We wrote on the User Guide as 6-18V input due to the limited minimum on time. With LMR14006X which operates at 1.1MHz, it should work well for the condition. But please still check the condition at different temperature as the minimum on time has some variance under different temperature. In datasheet, we only specify it at room temperature.

    Regards,

    Jerry

     

  • 0 in reply to Marc Davis-Marsh
    Expert 2600 points

    Dear Sir,

    May I know how to define the duty cycle of 0.1995  which you mentioned?

    I have a case of  LMR14006 for  Vin max 36v to vout 2.8V/300mA, can it use LMR14006X for this application? Thanks.

  • 0 in reply to Lucifer
    TI__Genius 10095 points

    0.1995 Duty Cycle minimum comes from the Minimum On-Time / Period which is equal to Minimum on-time x Frequency = 95ns x 2.1MHz = 0.1995.

    For the Case of 36Vin to 2.8Vout using the LMR14006X which runs at a lower frequency of 1.1MHz. 2.8V/36V = 0.077.  This is lower than than minimum duty cycle of around .1045 so the part will not be in fixed PWM operation.  The maximum voltage for fixed frequency operation will be around 26.8Vin for 2.8Vout.

    Regards,

    Marc

  • 0 in reply to Marc Davis-Marsh
    Expert 2600 points
    Dear Marc,
    How about LM2842? For 2.8V/36V = 0.077
    Min On time 100nS~150nS=0.055~0.0825
    Can LM2842 be used in this case? Thanks.
  • 0 in reply to Lucifer
    TI__Genius 10095 points
    Looking at the datasheet it looks like the LM2842X typical values would work. However looking at the absolute worst case for frequency and for duty cycle the design is marginal. Let me take a closer look at how these parameters change with temperature and get back to you.

    Regards,
    Marc
  • 0 in reply to Marc Davis-Marsh
    Expert 2600 points
    Dear Marc,
    After surveying the TI website it seems to have no similar part to substitute LMR14006.
    It is highly appreciated if you have another suggestion?Thanks.
  • 0 in reply to Lucifer
    TI__Genius 10095 points

    Hi,

    First off on the LM2842.

    I looked at the temperature data and it looks like the frequency and the minimum on-time worst cases are at different temperature extremes.  The highest frequency is at cold whereas the longest on-time is at hot.  So based upon this if you use the typical frequency 550kHz* the longest minimum on-time 150ns then you get a duty cycle limit of 0.0825.  This would allow a maximum input voltage of 34V before the frequency was no longer fixed.  So it might work for your application if you only expect some transients up to 36V.

    Another option, in a slightly bigger package is the LMR23610.  This is a 1 amp part with a lower switching frequency (400kHz) and a lower minimum on-time (60ns typ). This part although a little bigger would have no problems with this operating condition.

    Regards,

    Marc