LM3646: LM3646

Ian Wang

Part Number: LM3646

Hi Sir,

My customer looking for IR LED driver, control by Flash.

Could you pls advise if LM3646 is suitable one? Thanks.

Vendor	OSRAM	OSRAM
P/N	SFH 4725AS A01	SFH 4180S
Forward voltage(V)	2.65(@1A), 3.65max	2.95(@1A), 3.3max
Usage amount	3PCS	4~6PCS

Thanks, Ian.

over 5 years ago

0 Sean Zhou over 5 years ago

TI__Mastermind 22745 points

Hi Ian,

For IR LED driver application with a fast response time requirement, I strongly recommend our LM3643/LM3644(two-channel) or LM36010/LM36011(single channel). Because those device has integrated the IR mode which can respond with the "STROBE" pin very quickly. It means that you put the trigger signal to the "STROBE" pin and it can respond very quickly.

Sean

0 Ian Wang over 5 years ago in reply to Sean Zhou

TI__Mastermind 29700 points

Hi Sean,

Some questions as following,

IR mode which can respond with the "STROBE" pin very quickly

Q. What is the raising and falling time?

2. For SFH 4725AS 3PCS use a LM3644, and a LM36011 is OK.

Q. customer will need to use 2 LM3644, and 2 LM36011, if there are two I2C address for each part?

3. There are three mode in IR Mode: Boost, Pass Only, Timeout

Q. Timeout mode is not suitable for customer . What is the difference between Boost and Pass Only mode?

Thanks, Ian.

0 Sean Zhou over 5 years ago in reply to Ian Wang

TI__Mastermind 22745 points

Hi Ian,

Here is a great AN that can answer your most questions.

http://www.ti.com/lit/an/snva773/snva773.pdf

For LM3644, you can use LM3644+LM3644TT they have different addresses, but for LM36010, there is only one I2C address.

Boost mode means it will switch and Vin is not enough to driver output LED under a special current. Pass mode is like LDO mode which means the Vin is higher than Vout and internal switched will not switch.

Sean

0 Ian Wang over 5 years ago in reply to Sean Zhou

TI__Mastermind 29700 points

Hi Sean,

We can find the i2c slave address of LM3644(0x63),but cannot find address of LM3644TT.

What is the address of LM3644TT?

2. 3PCS SFH 4725AS is OK for driven by LM3644+ LM36011

But SFH 4180S just only can drive 5PCS by LM3644+ LM3644TT +LM36011, do you have any countermeasure?

Vendor	OSRAM	OSRAM
P/N	SFH 4725AS	SFH 4180S
Forward voltage(V)	2.9(@1A), 3.4max	2.95(@1A), 3.3max
Usage amount	3PCS	6PCS

Thanks,Ian.

0 Sean Zhou over 5 years ago in reply to Ian Wang

TI__Mastermind 22745 points

Hi Ian,

1. I'm sorry that LM3644TT has the same I2C address with LM3644, But you can try with LM3643 and LM3643A which has the different I2C address wit LM3643;

2. LM3643+LM3643A+LM36011 may be a good solution for 5 pcs LEDs.

Sean

0 Ian Wang over 5 years ago in reply to Sean Zhou

TI__Mastermind 29700 points

Hi Sean,

Thanks.

Do you have solution for 6PCS IR LED SFH 4180S?

Vendor	OSRAM
P/N	SFH 4180S
Forward voltage(V)	2.95(@1A), 3.3max
Usage amount	6PCS
TI solutions	?

Thanks, Ian.

0 Sean Zhou over 5 years ago in reply to Ian Wang

TI__Mastermind 22745 points

Hi Ian,

What's the supply voltage? And how about the LED configuration? All serially connected or can be connected parallelly?

I would recommend TPS54201 first.

Sean

0 Ian Wang over 5 years ago in reply to Sean Zhou

TI__Mastermind 29700 points

Hi Sean,

Serially is better, but can also consider others.

supply voltage is 3.2~5CV.

TPS54201 is still the better solution?

Thanks, Ian.

0 Sean Zhou over 5 years ago in reply to Ian Wang

TI__Mastermind 22745 points

Hi Ian,

No, TPS54201 is a buck topology LED driver, for this kind of high current application, usually, it will use buck topology.

If you are considering the boost LED driver, it may need a LED controller, from our team, you can try with TPS61500.

Sean

0 Ian Wang over 5 years ago in reply to Sean Zhou

TI__Mastermind 29700 points

Hi Sean,

Thanks for information

You means use TPS61500 be a solution for 6PCS IR LED SFH 4180S?

Thanks, Ian.

0 Sean Zhou over 5 years ago in reply to Ian Wang

TI__Mastermind 22745 points

Hi Ian,

I'm worried that the power is too high for TPS61500, I suggest using TPS54201 with a 24V power supply.

Sean

0 Ian Wang over 5 years ago in reply to Sean Zhou

TI__Mastermind 29700 points

Hi Sean,

Confirm again,

You means use TPS54201 be a solution for 6PCS IR LED SFH 4180S?

Thanks, Ian.

0 Sean Zhou over 5 years ago in reply to Ian Wang

TI__Mastermind 22745 points

Hi Ian,

Yes, you can use this for 6pcs LEDs.

Sean

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LM3646: LM3646