EVB90401 Datasheet, PDF (6/6 Pages) Melexis Microelectronic Systems – MLX90401 Demo Board

EVB90401
MLX90401 Demo Board
2.3 Optimum value of R1
The minimum value of resistor R1 is determined by the minimum power supply voltage available for the
chip. V_CHIP,MIN should be at least 8V (undervoltage V_UV) for the drivers to work.
V_CHIP,MIN = V_SUPPLY,MIN – R1 x I_CHIP
For example:
V_CHIP,MIN = 24V – 220R x 35mA = 16.3V
The maximum value of the resistor determines the power dissipation of the resistor:
P_R1 = (V_SUPPLY – V_CHIP) x I_CHIP
For example:
P_R1 = (24V – 15V) x 35mA = 315mW
For instance, if a standard 12V battery is used, make R1=100R.
V_CHIP = 12V – 100R x 35mA = 8.5V > V_UV = 8V
P_R1 = (12V – 8.5V) x 35mA = 122.5mW
V_SUPPLY
V_CHIP
R1
P_R1
(V)
(V)
(Ohm)
(W)
> 23.0
15
220
> 0.37
16.0
8.3
220
0.27
12.0
8.5
100
0.13
8.0
8.0
0
0.00
Table 1: Recommended value of R1 in function of supply voltage
(with DZ1 = 15V zener diode)
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ISO/TS 16949 and ISO14001 Certified
390119040101
Rev 002
Page 6 of 6
Application Note
15-Jul-05