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LM3410-Q1: LM3410-Q1

Gaurav Bankre
Prodigy 10 points
Part Number: LM3410-Q1
Other Parts Discussed in Thread: LM3410, TPS61288

Hi,

I am looking for a LED driver for my new product design which should be able to drive 98 laser diodes whose Vf= 2.4V and If= 70mA.

Input voltage to LED driver 3.3V.

LM3410-Q1 has around 85% efficiency for this input voltage.

Does TI have any better part than LM3410-Q1 or this one is good enough for the above application?

Thanks,

Gaurav

  • 0
    TI__Genius 15020 points

    What is output voltage? How many strings and LEDs number in series per string?  

  • 0 in reply to Xiaoguang1
    Prodigy 10 points

    Output voltage= 22V

    11 strings. 9 LEDs per string.

  • 0 in reply to Gaurav Bankre
    TI__Genius 15020 points

    Yes, this device is good enough for the application. 

  • 0 in reply to Xiaoguang1
    Prodigy 10 points

    As i mentioned in the start that i want to drive 98 laser diode with this LM3410 LED driver. Laser diode Vf= 2.4V and If= 70mA.

    Input voltage is from Li-pol battery (2.7V to 4.2V). There will be two arrays of 49 diodes.

     I want to control both arrays of 49 diodes separately through mosfet to turn them on/off like in the attached config1. But i am not able to find a way to separate out the FB pin for both arrays. is there any way or i need to use the 2 LED drivers to control them separately?

  • 0 in reply to Gaurav Bankre
    TI__Genius 15020 points

    I don't think LM3410 can be used this way. I thought you are using 11 LM3410, 1 LM3410 per string.

    1. All strings have same VLED voltage when they are paralleled together, it's impossible to have 9 x LED and 4 x LED in a group and light 9 LEDs normally. The string voltage will be clamped to 4 x VF (VF - LED forward voltage)  

    2. Need to calculate capability of power delivery with Vin,min. and make sure that peak inductor current is lower than 2.1A, (which is minimum value of switch current limitation) refer to 8.1.1.3 Inductor Selection for details. As you are using Li-pol battery, it's hard to light one array when VIn is low (like < 3.3V), no mention about 2 arrays together. 

    What is logic/mechanism for controlling the two arrays?  While according above two concerns, you need to use multiple LM3410. 

  • 0 in reply to Xiaoguang1
    Prodigy 10 points

    Will below configuration work for my application?

  • 0 in reply to Gaurav Bankre
    TI__Genius 15020 points

    Maximum output power Po,max= Vo,max * Iout = (7*VF,max +  VFB)* 0.07* 7 = 0.49 * (7*VF,max +  0.19)

    Assuming efficiency η = 83%, input current Iin, max = Po,max / η Vin,min;  

    As device minimum current limit is 2.1 A, considering ripple, Iin, max is preferred to be < 1.8A (+/- 15% ripple current）

    Thus, what is VF,max  value and what is vin,min value in this application? 

    Also, power loss in one chip should be less than 400mW. The solution above will definitely have thermal issue. 

    Can you consider using more LM3410? For example, one LM3410 per string? thanks. 

  • 0 in reply to Xiaoguang1
    Prodigy 10 points

    VF,max= 2.4V and Vin,min=3.2V

    Using one LM3410 per string would be costly for our application as we have to use so many.

    Could you please suggest any other part number which can be used for this application?

  • 0 in reply to Gaurav Bankre
    TI__Genius 15020 points

    you may consider using boost converter like TPS61288 etc. to convert 3.2Vin to higher voltage like 18V and use one device TPS929160 to control all 14 channels. In this way, uC need to use UART or CAN to control TPS929160.