MLX90614_15 Datasheet, PDF (40/51 Pages) Melexis Microelectronic Systems – Single and Dual Zone Infra Red Thermometer in TO-39

MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
11.3 PWM output operation
Using the PWM output mode of the MLX90614 is very simple, as shown in Figure 37.
J1
Vdd
PWM
GND
CON1
1
SCL
Vz
PWM
2 ^SDA
Vss
Vdd
U1
MLX90614
C1
3
0.1uF
Figure 37: Connection of MLX90614 for PWM output mode
The PWM mode is free-running after POR when configured in EEPROM. The SCL pin must be forced
high for PWM mode operation (can be shorted to V_DD pin).
A pull-up resistor can be used to preserve the option for SMBus operation while having PWM as a
default as is shown on Figure 38.
J1
Vdd
SCL
PWM/SDA
GND
CON1
R1
10k
1
SCL
Vz
PWM
2 ^SDA
Vss
Vdd
U1
MLX90614
C1
3
0.1uF
Figure 38: PWM output with SMBus available
Again, the PWM mode needs to be written as the POR default in EEPROM. Then for PWM operation
the SCL line can be high impedance, forced high, or even not connected. The pull-up resistor R1 will ensure
there is a high level on the SCL pin and the PWM POR default will be active. SMBus is still available (for
example – for further reconfiguration of the MLX90614, or sleep mode power management) as there are pull-up
resistors on the SMBus lines anyway.
PWM can be configured as open drain NMOS or a push-pull output. In the case of open drain external
pull-up will be needed. This allows cheap level conversion to lower logic high voltage. Internal pull-ups present
in many MCUs can also be used.
11.4 Thermal alert / thermostat
+5V
- _D1
Alert dev ice
+
2
PWM
SD A
V dd
3
SCL ¹
Vz
C1 U1
0.1uF
V ss
4 ^MLX90614Axx
+3.3V
R1 R2
2
PWM
SD A
Vdd
3
SCL ¹
Vz
C1 U1
0.1uF
Vss
4 ^MLX90614Bxx
SMBus
U1
Vdd
SDA
SCL
GND
MCU
+24V
R2
R1
Q1
2
PWM
SD A
Vdd
3
SCL ¹
Vz
C2
C3
V ss
4
C*
U2
10uF
0.1uF
AC line
Figure 39: Thermal alert / thermostat applications of MLX90614
3901090614
Rev 009
Page 40 of 52
Data Sheet
June 29, 2015