NSI45090DDT4G Datasheet, PDF (5/6 Pages) ON Semiconductor – Adjustable Constant Current Regulator & LED Driver

NSI45090DDT4G
Comparison of LED Circuit using CCR vs. Resistor Biasing
ON Semiconductor CCR Design
Resistor Biased Design
Constant brightness over full Supply Voltage
(more efficient), see Figure 10
Large variations in brightness over full Automotive Supply Voltage
Little variation of power in LEDs, see Figure 11
Large variations of current (power) in LEDs
Constant current extends LED strings lifetime, see Figure 10
High Supply Voltage/ Higher Current in LED strings limits lifetime
Current decreases as voltage increases, see Figure 10
Current increases as voltage increases
Current supplied to LED string decreases as temperature
increases (self-limiting), see Figure 2
LED current decreases as temperature increases
Single resistor is used for current select
Requires costly inventory
(need for several resistor values to match LED intensity)
Fewer components, less board space required
More components, more board space required
Surface mount component
Through-hole components
140
T_A = 25°C
120
Circuit Current with
100 _{CCR Device}
80
60
40
Circuit Current
20 with 83.3 W
0
9
10
11
Representative Test Data
for Figure 8 Circuit, Current
of LEDs, FR−4 @ 300 mm²,
2 oz Copper Area
12
13
14
15
16
V_in (V)
Figure 10. Series Circuit Current
800
T_A = 25°C
700
600 ^{LED Power with}
CCR Device
500
400 ^{LED Power}
with 83.3 W
300
200
Representative Test Data
for Figure 8 Circuit, Pd of
100
LEDs, FR−4 @ 300 mm²,
2 oz Copper Area
0
9
10
11
12 13 14
15 16
V_in (V)
Figure 11. LED Power
Current Regulation: Pulse Mode (I_reg(P)) vs DC
Steady-State (I_reg(SS))
There are two methods to measure current regulation:
Pulse mode (I_reg(P)) testing is applicable for factory and
incoming inspection of a CCR where test times are a
minimum. (t < 300 ms). DC Steady-State (I_reg(SS)) testing
is applicable for application verification where the CCR will
be operational for seconds, minutes, or even hours. ON
Semiconductor has correlated the difference in I_reg(P) to
I_reg(SS) for stated board material, size, copper area and
copper thickness. I_reg(P) will always be greater than I_reg(SS)
due to the die temperature rising during I_reg(SS). This heating
effect can be minimized during circuit design with the
correct selection of board material, metal trace size and
weight, for the operating current, voltage, board operating
temperature (T_A) and package. (Refer to Thermal
Characteristics table).
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