1. I have to connect a 3W white led light as here: http://tinyurl.com/jpj3gnu & control its intensity using a 10K potentiometer.

2. If = 0.7A
Vf min = 3.2V
Vf max = 4.0V

Input voltage range: 5.4V to 8.4V
I think TLE4309 should work in this application.

3. Max adjustable current in IC: 500mA
So to be on same side I keep max 450mA.

Vref = 178mV.(From table)
so Rref = 178mV/450mA = 0.3955ohm

This is very close to 0.39ohm minium of Rref. Should I select higher resistance value then this r this is also ok? But if I go higher then Iref will reduce further & led will glow less.

4. Pin connection
Pin1: Connected to input voltage 5.4V to 8.4V, decoupled by 0.1uF
Pin3: Open
Pin4: Ground
Pin5: 0.39ohm shunt
Pin6: Open
Pin7: Led connected


Query:
1. Now I want to control the intensity of the led through 10K potentiometer. How do I do it?
Should I connect one terminal of potentiometer to pin1 i.e input, third terminal to pin4 i.e ground
and middle pin of pot to Pin2 of TLE4309.
Will this work?

 

Will this work?

No. Read the datasheet. Pin 2 needs a PWM signal with a variable duty cycle to control brightness. You could use a 555 to generate the PWM signal, controllable with your pot.

 

This chip is not intended for linear dimming, the PWM/ENABLE input is a logic input, it expects a digital PWM input to dim the lights.

You could use a 555 timer to generate the PWM signal to drive this input.

 

Attached find a file named board. This is the circuit which works with potentiometer directly. A 10K pot is connected, varying it vary the led intensity linearly.
Package of IC is TO263-7, I think
Attached find schematic file. It is the reversed schematic of the board.

I had looked for many IC from different vendors for Led driver application in TO263-7 package. But they all are PWM control.

What is that IC.?
This board works ok.

 

Post deleted

 

1. From led datasheet
If = 0.7A
Vf min = 3.2V
Vf max = 4.0V

Input voltage range: 5.4V to 8.4V . Max current we can limit is 0.5A

2. Attached find a workable board which i found in a device. It is used for led dimming using 10K pot & IC is TO263-7 package. I dont know which IC is this as there is no name on it.
SO I removed the IC from it & attached find its pic also.

3. I have also attached its reverse schematic. I think they have placed 10K in series with 22K which goes to REF pin. If we do thevenin equivalent at REF pin, it seems that the ckt changes voltage at REF pin, so that it sense more current at pin REF pin & created the dimmming effect.

4 Can I do the equivalent in TL4309 with below connections:
Pin1: Connected to input voltage 5.4V to 8.4V, decoupled by 0.1uF
Pin2: Dont know what do connect?
Pin3: open
Pin4: Ground
Pin5: same ckt as in attached schemtaic. Five 1.8ohms, one 470ohm, 22K & 10k pot.
Pin6: Open
Pin7: Led connector

 

Is this classroom work, or is there a real purpose to it?
There are buck convertors with input V range of 4.5 V to 30 V, & constant V or constant current up to 5 A. on eBay. Current controlled by a pot. 10k ?