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LM3668 EVM is not giving 1 A with 2.5 to 5.5 V

vengadesh uthirapathy
Intellectual 770 points
Other Parts Discussed in Thread: LM3668

Hi ,

One of my customer brought the LM3668 EVM , they are feeding 2.5 v to 5.5 V & output they are trying for 3.3 V with output of 1 A .

Even they have tried in forced PWM Mode , could you please give step to achive the  1 A with 2.5 to 5.5 V in both modes.

Regards/

vengat

 

 

  • 0
    TI__Intellectual 1955 points

    Hi Vengat,

    I happened to stumble on this query and it appears no one has offer any hint.  Actually ,this is a fairly common issue, mostly due to power supply with inadequate power of current limitation.  I have a 3 Amp supply and set it to full current, for Vout=3.1V , RL=3.0 ohms 5% 5W resistor, at Vin>=3.7V you will get 1A+.  At lower Vin the current available is pulled back  as indicated in the data sheet.  (I have an engineering part for 3.2/3.6V, not sure the factory settings were.)  At low Vin the supply must have sufficient power (Iin *Vin product) to support Iout*Vout.  

    DS: For the 4.5V/5.0V option:1A maximum load current for VIN = 3.9V to 5.5V

            For the 2.8V/3.3V and 3.0V/3.4V options 1A maximum load current for Vin = 2.8V to 5.5V

    I got a hold of a normal EVB for Vo=2.8V/3.3V Iout=1A is achievable down to Vin=2.6V .    Hope this note will be helpful for the future.

    Kern