JAJSOJ3A March 2022 – May 2022 LP5891
PRODUCTION DATA
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Figure 7-11 shows the caterpillar issue caused by open LED. Suppose the LED0-1 is an open LED. When line 0 is chosen and the OUT1 is turned on, the OUT1 voltage is forced to approach to VLED because of the broken path of the current source. However, the voltage of the un-chosen lines are below the Vclamp which is much lower than VLED, causing all LEDs which connect to the channel OUT1, light unwanted.
The LP5891 implements circuits that can eliminate the caterpillar issue caused by open LEDs. The LED open caterpillar removal function is configured by LOD_RM_EN (see FC0 for more details). When LOD_RM_EN is set to 1b, the caterpillar removal function is enabled. The corresponding channel OUTn is turned off when scanning to line with open LED, The caterpillar issue is eliminated until device resets or LOD_RM_EN is set to 0b.
The internal caterpillar elimination circuit can handle a maximum of three lines that have open LEDs fault condition. If there are open LEDs located in three or fewer lines, the LP5891 is able to handle the open LEDs all in these lines. If there are open LEDs in more than three lines, the caterpillar issue is solved for the lines where the first three open LEDs were detected, but the open LEDs in the fourth and subsequent lines still cause the caterpillar issue.