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Led driver choice for MKR cree led

lead chem
Prodigy 30 points
Other Parts Discussed in Thread: TPS61500, LM3429, LM3421

Hello everbody, 

I would like to drive one MKR cree led with analog dimming. Which driver model could you advice me ?

Vin is from 2,7 to 5,5V and (Lithium-ion batterie or USB connection).

iLED have to be around 500mA

I saw on Ti website TPS61500 driver with analog dimming from a PWM signal. Is it a good choice ?

Thank you for your help,

Lead

  • 0
    TI__Expert 5130 points

    Hello Lead,

    What is your LED forward voltage? Will you consider PWM dimming method?

    Best regards,

    Victor

  • 0 in reply to Victor Chen_HK
    Prodigy 30 points

    Hello Victor,

    Thank you for your message.

    The LED forward voltage for MKR led is between from 10,5V to 12V. 

    I prefer to have a analog dimming to insure to have the best efficiency with my led. Use a microcontroler with DAC can be a solution. I saw also that TPS61500 can drive a led wby analog dimming with a PWM signal.

    What do you think ?

    Thank you,

    Lead

  • 0 in reply to lead chem
    TI__Expert 5130 points

    Well, I am not familiar with that part but if you are using a input voltage larger than 4.5V, you may try LM3421/LM3429.  They are high side current sensing controller with UVLO, OVP and thermal shutdown and both of them can do PWM and analog dimming.

    -Victor

  • 0 in reply to Victor Chen_HK
    Prodigy 30 points

    Hey Victor,

    Thanks for your help

    I checked the datasheet for LM3421 & LM3429.  Both drivers can be drive by PWM or analog but :

    - Vin is from 4,5V to 75V :  In my case, my led must work with the input voltage from 2,7 to 5,5V because I'm using a Lithium-ion battery (2,7V to 4,2V) and some time I will connect my system directly to usb connection (5V).

    - iLIM is only 1A (1A Peak MosFET Gate Driver) : but I need at least 2A because LED Power at 0,5A is 5,75W (0,5A x 11,5V). If I consider a 90% efficiency, Input Power need to be 5,2W (5,75 x 90%). The Lithium-ion battery voltage can discrease until 2,7V. So, to still provide a 5,2W, Input current is getting to roughly 2A (5,2 / 2,7 = 1,9).

    I'm continuing to find a driver which can fit to need but I didn't find it. Somebody else can help me ?

    To sum up my needs : 

    Vin : 2,7 to 5,5V

    iLIM : min. 2A

    iLed : 0,5A

    Vled : 10,5V to 12V

    Thank you,

    Lead