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LM5005: Issue with reference design.

Steven Shenker
Intellectual 830 points
Part Number: LM5005

Hi there,

I have 2 questions with using this device. 

1. The RC snubber network suggested by the reference design doc (SNVS397E –SEPTEMBER 2005–REVISED NOVEMBER 2016) on pg 23 suggests a 1 Watt resistor for Rs. IE: 10 Ω, 1 W, 1206

Is this 1W value really sufficient - surely the full output voltage (e.g 5V) is seen by this resistor? Meaning a 0.5 A current drop and 2.5 Watts?

2. Does the device require a minimum load, I have been using the reference design in the PDF and it mentions a minimum load current of 250mA on pg 17 - does this mean for this design to work the output at Vout must always have 250 mA minimum?

Thanks in advance for your help!

  • 0
    TI__Mastermind 27030 points

    Hi Shenker:

    1. the resistor of RC snubber is for cosume the Csnubber votlage when the diode conducut. so the power dissiapation will be around from 0.5*C*Vin^2*fsw-C*Vin^2*fsw

    2. the minium load if for keep the inductor in the continue conduct mode(CCM). in no load condition or less than 250mA, the inductor current will go to zero, so the duty not equal to Vo/Vin.

    Thanks

    Daniel Li