Mofet Thermistor (Option) - Renesas RAJ306010 User Manual

RAJ306010 RSSK(RTK0EML2C0S01020BJ)
4.3.3.

MOFET thermistor (Option)

The thermistor(Z1) is mounted to measure MOSFET temperature. By default, the on-board thermistor (Z1) is
available by mounted 0Ω register of the MOSFET thermistor selection resistor(R106) and the on-board
thermistor (Z1) is connected to P21 (ANI1).
When using an external thermistor, it can be used by removing the 0Ω resistor mounted on the R106 and
connecting a thermistor between P21 (1Pin) and GND (2Pin) of CN_INV.
The following shows the calculation formula of the thermistor resistor value and a calculation example of the
relationship between the temperature of the MOSFET thermistor (Z1) used on the board and the input voltage of
ANI1. Figure 4-4 shows how to get the resistance of the thermistor mounted on the board at a specific
temperature T and how to get the ADC conversion result from the resistance. Determine the threshold value
from here.
Figure 4-5 shows an example calculation of the relationship between the temperature of the MOSFET thermistor
(Z1) used in this board and the input voltage of ANI1.
Table 4-5 shows examples of actual measurements.
This data is just an example and does not guarantee the performance.
Note 1 The MOSFET thermistor is optional and is not used in the initial firmware. When using a MOSFET
thermistor, please add to the firmware by the user.
R = R ∗ exp
TH 0
R + 65536
ADCR =
TH
( R
+ R
0
5.00
4.00
3.00
2.00
1.00
0.00
Ambient Temperature
ANI1 voltage calculation evaluation
ANI1 actual voltage
ADCR value calculation evaluation
ADCR register actual value
R18UZ0078EJ0100 Rev.1.0
Mar 24, 2021
Note1
1 1
R
�B� T − ��
T ADCR: RL78 10-bit ADC conversion result register (10 bits, top-justified)
TH
0
[Ω]: Thermistor resistance at T
R [Ω]: Reference resistance at T
+ 32
0
) B[K]: B constant (3350-3399K)
T[K]: Thermistor temperature (t°C + 273°C)
TH
T [K]: Reference temperature (25°C + 273°C)
0
Figure 4-4. Formula for calculating the thermistor resistor
ANI input voltage and estimated
Thermistor estimated temper (degree)
Figure 4-5. Thermistor (Z1) temperature and ANI1 input voltage
Table 4-5. Thermistor Temperature Data for MOSFETs (Reference)
0°C
4.91V
4.91V
0xFBC0
0xFB80
0
25°C 50°C
4.76V 4.44V
4.75V 4.42V
0xF340 0xE380
0xF340 0xE680
75°C 100°C
3.94V 3.28V
3.89V 3.21V
0xC940 0xA880
0xC780 0xA440
4. Function
125°C
2.58V
2.50V
0x83C0
0x8080
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