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I want to use above device for following power supply.
Vin:5.4V to 6.6VVout:1.25V/1A
Q1:LM27341-Q1I calculate "On Time" of following condition using equation(11),(12) of data sheetand it is 109ns. Vin:6.6V Vout:1.25V Fsw:2.3MHz Vd1:0.5V Rdson:0.15ohm Iout:1A
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-Q1I 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.
Please anyone respond my previous questions dated Feb 11 2013.
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In reply to Toshio Ushikubo:
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.
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?
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.
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