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Constant Current Regulators Slide 19

The CCR is a very simple device and does not need temperature compensation because it has a negative temperature coefficient. The graph on the left is for a 20 mA CCR in a SOD-123 package. At an ambient temperature of +25 C, the current is regulated at 20 mA. At an ambient temperature of -40 C, the regulating current is approximately 23 mA. At a temperature of +85 C, the regulating current drops to approximately 17 mA. The graph on the right is for a 30 mA device in a SOT-223 package. This graph shows a similar change in current as the temperature increases. The larger SOT-223 is more thermally efficient compared to the SOD-123 package and thus has improved regulation. The negative temperature coefficient of the CCR protects LEDs as temperature and voltage increase.

PTM Published on: 2011-11-03