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.

  • Resolved

LM27341-Q1 and LM2734Z-Q1

Mastermind 9620 points

Replies: 4

Views: 582

I want to use above device for following power supply.

Vin:5.4V to 6.6V
Vout:1.25V/1A


Q1:LM27341-Q1
I calculate "On Time" of following condition using equation(11),(12) of data sheet
and it is 109ns.
 
  Vin:6.6V
  Vout:1.25V
  Fsw:2.3MHz
  Vd1:0.5V
  Rdson:0.15ohm
  Iout:1A   

      -----11

  -----12

LM27341-Q1 data sheet has "Minimum on time:65ns typical", and no maximum value.
So I can't judge if 109 ns is OK or not.
Please advice if I can use LM27341-Q1 for above application.

Q2:LM2734Z-Q1
I calculate "Duty Cycle" of following condition using equation(11),(12),
and it is 25.9%.
 
  Vin:6.6V
  Vout:1.25V
  Fsw:3.6MHz
  Vd1:0.5V
  Rdson:0.34ohm
  Iout:1A
 
LM2734Z-Q1 data sheet has "Minimum Duty Cycle:8% typical", and no maximums value.
So I can't judge if 25.9% is OK or not.
Please advice if I can use LM2734z-Q1 for above application.

Regards.

  • Hello,

    Please anyone respond my previous questions dated Feb 11 2013.

    Regards.

  • In reply to Toshio Ushikubo:

    Hello Tony,

    This post somehow slipped our radar.

    The LM27341 has a minimum on time of 65ns as you saw in the datasheet. This can be realized as follows:

    ton(min) = Vout/(VinMax*Efficiency*Frequency). Assuming an efficiency of 90%, the resulting ton is about 90ns. This is more than 65ns and therefore this design is possible. You could use Webench to create a design for your requirements.

    The LM2734Z has a maximum duty cycle of 85% (pg. 4 of D/S). Therefore for your requirement the LM2734Z would work. Again, you could use Webench to create a design using this part. The default frequency is 3MHz.

    I hope this information is helpful.

    Regards,
    Akshay 

  • In reply to Akshay Mehta:

    Hello Mr. Akshay,

    Thank you for your reply.

    LM27341 Minimum on time 65ns of D/S is typical and D/S does not have maximum value, so I want to

    know haw many margins are required to get safety design.

    For LM2734Z, I have same kind of question. Duty Cycle of my power supply requirement(I already posted)

    is around 29% and it satisfy Maximum Duty Cycle 78%(minimum), but Minimum Duty Cycle pf D/S

    is 9% typical and does not have maximum value.

    How many margins are required against 9% typical of D/S to get safety design?

    Regards.  

  • In reply to Toshio Ushikubo:

    Hello Tony,

    We do not have guaranteed min and max values over temperature. The calculations are all done with the typical value. For your conditions this should not be a problem. I hope this helps.

    Regards,
    Akshay 

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.