• State Resolved
  • Locked Locked
  • Replies 1 reply
  • Subscribers 64 subscribers
  • Views 310 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LM2759: current accuracy, external components , sequence

Ryuji
Guru 20090 points
Part Number: LM2759

Hello,

I have some questions about LM2759.

(1) Sequence of Torch mode
Our customer use LM2759 with I2C control only (not use TX and STROBE pin) and use Torch mode only (not use Flash mode).
Could you please let me know the recommended sequence in this case?

For example, 
1:Strobe and TX pins are connected to GND
2:Vin Power on
3:Set the Torch current register to desired value (40mA) 
4:Control the Torch or Shutdown mode via General Purpose Register setting 

(2) Current accuracy
Could you please let me know the current accuracy when we set the Torch current to 40mA?
Since the LED current rating is 45mA(max), they may need 10% accuracy.
Can we use +/-10% accuracy in the datasheet for torch current 40mA?

(3) External capacitors
There is the suggested capacitors in datasheet table 5.
If the capacitance value, the voltage rating, and the characteristics of X5R are satisfied, is the package size smaller than the one shown in the data sheet Table 5?

Best Regards,
Ryuji 

  • 0
    TI__Intellectual 1940 points
    Hello,
    1) Yes you are correct.
    2) Accuracy is only specified at 220mA. Accuracy outside of this range is not guaranteed and can have a wider or smaller variations in current. In general, accuracy at lower currents tends to yield wider limits due to the size of any offsets becoming a larger percentage of the total. So to answer your question, no you cannot assume +/-10% will hold at 40mA
    3) The package size can definitely be smaller for a given set of equivalent specs, however as case size decreases, so does the effects of DC Bias. So, you will need to compare the DC bias curve for capacitor mentioned in the datasheet with the one the customer wants to use to see if the effective capacitance is equivalent.

    Greg