LP5521 - Is the part capable of true 100% output (LEDs continuously ON) ?

Zbynek Jerie

Other Parts Discussed in Thread: LP5521, LP55231Part Number: LP5521

Application: LED Constant current driver

Question type: Device selection assistance

Support topic: /Product/Device selection assistance/

Description of the problem: We have 6 independent LEDs (they are not even RGB combination ) in our system to drive (they are single UV-diodes with Ufwd = 4V max.).
We specifically need 100% PWM output = no OFF time, just controll the LED current over I2C.
LP5521 is the only part that we've found and that seems suitable. A lot of other LED drivers seem to offer "constant current LED drive" but after a lot of reading in datasheets one finds out, that they are incapable of true 100% PWM (many go up to 99.6% for example...).
So is LP5521 the right part to use for 100% PWM and setting of the continuous LED current through I2C ?
Is there even a better part ? For example with more outputs (since we have 6 Diodes)?

Thank you,
Zbynek

over 8 years ago

0 Hak-Leong Ng over 8 years ago

TI__Intellectual 1985 points

Hi Zbynek,

Not sure how much current you need for each LED, if LP5521 is okay for you, you can also check out LP55231, this is very similar to LP5521, but it can drive 9 LEDs, 6 of them is power by the charge pump and 3 of them is power by Vin.

Regards

H L

0 Zbynek Jerie over 8 years ago in reply to Hak-Leong Ng

Prodigy 30 points

Hello Hak-Leong Ng,

thank you for the tip - the LP55231 should be ok regarding the max. current and the number of Outputs. Approx. 20mA per Diode should be enough in our application.

As for the main part of the question: Is it really capable of 100% PWM, that is continuous Output by Setting the

Dx PWM [7..0] Register to 255 ? Will there be no OFF periods ?

0 Hak-Leong Ng over 8 years ago in reply to Zbynek Jerie

TI__Intellectual 1985 points

Hi Zbynek,

If PWM code is set to 255, it is 100% PWM, i.e. a flat high level, no off period.

Regards

H L

0 Zbynek Jerie over 8 years ago in reply to Hak-Leong Ng

Prodigy 30 points

Hello Hak-Leong Ng,
thank you very much. This helped us a lot.
Zbynek

Power management

Power management forum

LP5521 - Is the part capable of true 100% output (LEDs continuously ON) ?