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LM3435: current setting and efficiency

Hardy Xue
Expert 3640 points
Part Number: LM3435
Other Parts Discussed in Thread: LM3549

Hi Team,

We have 3 questions for LM3435 datasheet as below. 

1. Do we have efficiency comparison for 500kHz and 1MHz switching frequency?

2. For High Current Regulator, could we use larger than 49.5k ohm for RIREFX to get lower ILEDX according to datasheet? Because the customer's current application is about 0.3A~0.4A.
Now, customer use 61.9k ohm RIREFx but they sometimes found that the fault pin was triggered when low current condition.

3. If we use 49.5k ohm for RIREF, the LED current setting is 0.5A. Does it mean IMIN = 0.5A/1024 = 0.48mA? Does it can meet +/-3% accuracy?

Best regards,

Hardy

  • +1
    TI__Genius 9255 points

    Hi Hardy,

    1. We don't provide the efficiency comparison for 500kHz and 1Mhz. The efficiency is also impact by the external element.

    2. The LED current setting can be in the range of 0.5A up to 2A, so it is not suggested to use larger IREF. But customer can reduce the average current by changing the duty of PWM control.

    3. The +/-3% accuracy is the typical spec, in low current output the accuracy of device will be worse.

    In addition, will you consider another device LM3549? The maximum drive current is 700mA and has 95% peak efficiency buck-boost converter.

    Best Regard 

    Monet Xu