NSI50350AST3G

http://onsemi.com

4

APPLICATIONS INFORMATION

The CCR is a self biased transistor designed to regulate the

current through itself and any devices in series with it. The

device has a slight negative temperature coefficient, as

shown in Figure 2 – Tri Temp. (i.e. if the temperature

increases the current will decrease). This negative

temperature coefficient will protect the LEDS by reducing

the current as temperature rises.

The CCR turns on immediately and is typically at 20% of

regulation with only 0.5 V across it.

The device is capable of handling voltage for short

durations of up to 50 V so long as the die temperature does

not exceed 175

°C. The determination will depend on the

thermal pad it is mounted on, the ambient temperature, the

pulse duration, pulse shape and repetition.

Single LED String

The CCR can be placed in series with LEDs as a High Side

or a Low Side Driver. The number of the LEDs can vary

from one to an unlimited number. The designer needs to

calculate the maximum voltage across the CCR by taking

the maximum input voltage less the voltage across the LED

string (Figures 7 and 8).

Figure 7.

Figure 8.

Higher Current LED Strings

Two or more fixed current CCRs can be connected in

parallel. The current through them is additive (Figure 9).

Figure 9.