Looking for 1A output 4channel individually controllable LED driver

Hello Chris,

That depends. Could you provide more information? It would be useful to know the following:

1. Input voltage range

2. LED load information. It sounds like 4 LED strings. How many LEDs in each string and what is each LEDs forward voltage drop? How much current does each LED need to run?

3. Do you need dimming? If so analog or PWM dimming?

If you can provide that information we can see if TI has anything that fits.

Thanks,

Clint

Hi Clinton,

Thanks for the reply. Sorry for my lack of description.

Each channel I'm looking to drive a singular LED at 700mA or 1A preferred, something like 3-3.5 V on the led drop. So each LED string would be a singular LED at over 3W.

Input voltage would be on the lower range from other drivers I've seen, I could supply anywhere from 5V to 11V or possibly higher if that was an input requirement.

I would like to have each dimmable separately preferably through PWM input and a frequency of LED output of at least 1 KHz.

Overall I would not push 12W continuously through the driver, maybe 6 max continuous.

Does that help? Thank You!!

Hello Chris,

I am not aware of any 4 channel buck converters that can do 1A each channel. I will copy this to someone in another group that might know differently. But if you want to drive and control each with a separate regulator there are some very good options. The smallest would be the LM3405, but that only provides PWM dimming and not analog. You could also look at the LM3414 or the TPS92515. They both have analog and PWM dimming. The TPS92515 will have the widest range for analog dimming. Let me know if you have any questions on any of them.

Thanks,

Clint

Clint,

Very helpful! Thanks very much! I'll review

Hi Clint,

I'm circling back to this because I've ran into a slight snag with power efficiency. I've moved towards regulating each LED with a single module, like the LM3405, but the efficiency of this IC when controlling a singular LED is around 80% when run at a full 1A. Would this be pretty standard or would there be another product or topology that has a higher efficiency for singular high output LEDs?

Thanks!

Hi Chris,

Actually a buck topology is about the most efficient there is all things considered. The LM3405 is probably not the most efficient since it was designed for very small size (1.6MHz switching frequency). Basically the main thing to consider is the switch Rds(on) and the diode forward voltage drop. With a buck if the duty cycle is high (Vin close to Vout) the main loss is the FET Rds(on), but if it is low (Vin much higher than Vout) the diode is burning most of the power. So if efficiency is the main concern you generally want to run at a pretty high duty cycle with an integrated FET buck. If you need really good efficiency at low duty cycle you generally need to consider a synchronous buck such as the TPS92640 controller. You could get some improvement with a non-synchronous buck such as the LM3409 simply because you can pick a very low Rds(on) switch as it's a controller, but you can only get so much improvement with diode selection.

Generally 80% is about typical for low duty cycle and high switching frequency like the LM3405, but you can do significantly better if size is not your main concern.

Best regards,

Clint

Hi Clint,

In trying to make a driver selection I had a pseudo scope creep. I've done my best to pour over some of the multitude of drivers here, but haven't perfectly found what I'm looking for.

The scope creep was in adding battery runtime, Lithium Ion (so operating 3.7 - 3V when mostly discharged) and found the LM3410 accepting that input voltage, but I didn't get a feel if it could do 2.8A continuous or only in flash mode, would you mind clarifying that one? It says 1.5A output on the catalog view, but 2.8 peak in the spec sheet.

Also along with this I'm trying to assess if I can drive two different LED architectures with the same driver, and so would be looking for a 2.5A or higher output driver. The TPS92640 had that capability but too high of an input range for a Li-Ion.

I apologize for a redo but here would be the characteristics (for clarification)

Input Voltage: 3.7V down to ~ 3V on Li-Ion range

Output Voltage: ~3V Single High Brightness LED

Output Current: Minimum 1.5A

Dimming Input Signal: PWM only needed.

Thanks once again for your assistance. Would a buck/boost converter be a good thing to look at here? If so I would probably need automatic switching, would something like the TPS63070 fit the bill here?

Hello Chris,

The LM3410 is the only device in our particular group that can go to such a low input voltage, we generally deal with higher power/input voltage applications. But to answer the question the 2.8A spec is a peak current limit spec. In a boost the input current will be higher than the output current though so you cannot do 2.8A at the output, what you can do all depends on total output power. With your new specs the LM3410 sepic should be able to do 1.5A but I am not sure how much more without testing it but I would guess up to about 2A if you are careful with thermal design.

In any case it looks like the TPS63070 would actually work pretty well also. It has a higher switch current limit so you could get more power and it is already designed as a buck-boost.

Regards,

Clint

Thanks guys! Good stuff there!