EVB10803 Melexis Company, EVB10803 Datasheet - Page 5

• Manufacturer Part Number: EVB10803
• Description: Evaluation Board Evb10803 Power Led Driver For Automotive Applications
• Manufacturer: Melexis Company

NTC selection according to the corresponding NTC datasheet. A standard NTC (e.g. BC components, part no.
2322 640 55474) with a nominal value of:
It has a resistance of:
To get the 47k on IREF1 at T=85° C, a resistor of:
has to be added in series to the NTC.
With this selection, R
If the temperature increases further, the resistance of the NTC drops even more and lowers the voltage on IREF1.
This way, the current threshold level at RSENSE is lowered which results in a lower peak current and thus, a lower
average LED current. Less current through the LED(s) generate less heat which increases the NTCs resistance
again: the current threshold level at RSENSE is increased and as a consequence, the average LED current rises
again. Depending on the thermal design and the ambient temperatures of the module, the regulation works faster
or slower around the adjusted corner temperature point.
The following schematic shows the connection of an external temperature sensor to the EVB10803:
V
V
R
R
R
R
R
390121080301
20/Mar/2006
Author: SSZ
IREF
IREF
NTC
NTC
IREF
7
7
Figure 4: External NTC for temperature down regulation
1
(
2
(
1
T
T
10
R
85
25
IREF
.
. 2
95
I
R
C
C
REF
35
NTC
)
)
1
k
V
2
(
36
T
470
R
@
R
85
NTC
.
Rev. 5.01
IREF
05
T
k
C
Start
(
)
T
NTC(T=25° C)
k
2
85
R
was selected.
C
7
50
)
R
at T=85° C .
IREF
47
A
= 470k and R7= 10.95k , the temperature regulation starts from T
k
( 1
47
T
k
85
C
36
)
.
05
. 2
Evaluation board EVB10803
47
35
k
Power LED driver for automotive applications
k
V
amb
= 85° C.
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