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ADPD107 Drive current settings not matching datasheet formula

Question asked by szabadaba on Dec 7, 2017
Latest reply on Dec 9, 2017 by jimmyreynolds

Hi Buckley,

 

We are seeing what looks like inaccuracies in the drive current on the ADPD107. The datasheet says the drive current should be:

 

LEDPeak = (50.3 + 19.8 * ILED_COARSE) * (0.74 + 0.022 * ILED_FINE) * (0.4 + 0.6 * ILED_SCALE)

 

We are trying to use these settings create a range of LED drive currents, and we are seeing this behavior:

You can see that the measured response (on a constant material), has some point where an increase would be expected but a decrease occurs. These point also appear to align with changes in the 'scale' setting. Note that the scale variable is multiplied by 10 to make it easier to see in the plot.

 

Is the equation in the datasheet accurate? I am also attaching a table of the data (PD is response, drive_i is expected drive current):

PDcoarsedrive_ifinescale
935.440677966016.6593640
1057.40229885018.4299280
1118.95454545019.3152100
1181.18823529020.20048120
1241.93023256021.08576140
1426.37647059121.9833620
1387.70114943023.29896190
1614.46987952124.4508860
1701.94047619125.6846480
1794.60465116126.9184100
1936.65116279228.1926420
2058.68965517229.7748840
2100.72619048131.23656170
2291.37647059232.9393680
2419.96470588334.4019220
2523.6741573236.10384120
2566.27380952138.02224280
2690.70786517139.87288310
2964.93975904441.750830
2169.70114943043.861661
2306.63855422046.074881
2448.85416667048.288101
3566.15853659350.81304190
3765.92941176553.3896870
3916.85227273656.0059240
4091.47727273458.8448180
4226.15853659861.775200
3416.71764706064.887251
4597.01190476467.9616260
3769.11494253071.5266311
4301.30681818175.007151
5148.85365854779.18688140
4650.88235294182.718201
5403.255813951086.6070460
5572.18823529891.16016160
5706.42528736995.7872140
5811.9397590411100.5911290
5891.5411764714105.58630
6028.6363636410110.64248170
6132.563218398116.872300
5825.176470593122.2058171
6255.3837209312128.28824170
6314.6111111110134.67792280
5995.15476193141.513251
6385.3617021312148.5564250
6046.012048193155.9934311
6416.2424242412163.75752310

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