LM3410-Q1: LM3410-Q1

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

Output voltage= 22V

11 strings. 9 LEDs per string.

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?

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. 

Will below configuration work for my application?

Maximum output power P_o,max= V_o,max * Io_ut = (7*V_F,max +  VFB)* 0.07* 7 = 0.49 * (7*V_F,max +  0.19)

Assuming efficiency η = 83%, input current I_{in, max} = P_o,max / η V_in,min;  

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

Thus, what is V_F,max  value and what is v_in,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. 

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?