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 on Figure 24.
J1
Vdd
1
SCL
Vz
PWM
SDA
Vss
PWM
2
U1
MLX90614
GND
Vdd
3
C1
CON1
0.1uF
Figure 24: 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
(can be shorted to Vdd pin) for PWM mode operation.
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 25.
R1
10k
J1
Vdd
1
SCL
Vz
SCL
PWM
SDA
Vss
PWM/SDA
2
U1
MLX90614
GND
Vdd
3
C1
CON1
0.1uF
Figure 25: 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
+24V
Q1
+3.3V
R1
R2
-
D1
Alert dev ice
+
R1 R2
U1
Vdd
MCU
2
2
2
PWM
SDA
PWM
SDA
PWM
SDA
SDA
SCL
GND
1
SCL
Vz
SMBus
Vdd
1
1
SCL
Vz
SCL
Vz
3
Vdd
Vdd
3
3
Vss
4
C3
0.1uF
C2
Vss
4
Vss
4
C*
U1
U1
C1
C1
MLX90614Axx
MLX90614Bxx
10uF
U2
0.1uF
0.1uF
AC line
Figure 26: Thermal alert/thermostat applications of MLX90614
The MLX90614 can be configured in EEPROM to operate as a thermal relay. A non contact freezing or
boiling prevention with 1 mA quiescent current can be built with two components only – the MLX90614 and a
3901090614
Rev 003
Page 31 of 40
Data Sheet
03/Oct/2007
MELEXIS [ Melexis Microelectronic Systems ]
