AND8349-D Datasheet, PDF (4/6 Pages) ON Semiconductor – Automotive Applications The Use of Discrete

Vbat (+)
AND8349/D
MBRS140T3G
(Reverse Protection Diode)
Jumper(s) selects DUT
Bias Resistor
(250 W)
NSI45030T1G
(CCR)
V_LED
Test Point
Vbat (-)
Jumper(s) to add/remove
LED from circuit
Figure 8.
NSI45030T1G
(CCR)
HF3-R5570
(3 red LEDs)
CCR Demo Board
This demo board (Figure 8) is the circuit shown in
Figure 6. It is used to generate several curves and can be used
to validate the CCR operation.
Figure 9 shows a comparison of power dissipation in a
CCR vs. Power dissipation in a Bias Resistor over battery
voltage variation from 9 V to 16 V. The CCR Power is less
than a Bias Resistor at higher operating voltages. At higher
Battery voltage, a higher wattage Power resistor would be
required increasing the circuit cost.
Figure 10 shows a typical Current / Voltage curve for a
CCR device. ON Semiconductor’s CCR is designed to have
400
350
300
250
200
150
P_d CCR (mW)
100
P_d Resistor (mW)
50
0
9
10 11
12 13 14 15 16
V_in (V)
Figure 9. CCR P_d vs. Resistor Pd
a slight negative trend as the power dissipation increases.
This negative trend reduces the power dissipation in the
CCR compared to the increasing power dissipation for a bias
resistor (Figure 9) and helps to prevent thermal runaway.
Since reduction in current is small, the change in LED
intensity is minimal.
Figure 11 shows thermal estimates for the NSI45030T1G
device with various heatsink footprints. If the heatsink area
is increased, the ambient operating temperature may be
increased. It is up to the circuit designer to understand the
thermal environment of the application and allow for device
thermals as specified in the device data sheet.
35
30
25
20
15
10
0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10
V_AK, ANODE−CATHODE (V)
Figure 10. CCR−IV Characteristics @ 25₅C
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