Data Sheet

MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
3901090614 Page 26 of 52 Data Sheet
Rev 008 February 28, 2013
8.6 Switching Between PWM / Thermal relay and SMBus communication
8.6.1 PWM is enabled
The diagram below illustrates the way of switching to SMBus if PWM / Thermal Relay is enabled
(factory programmed POR default for MLX90614 is SMBus, PWM disabled). Note that the SCL pin needs to be
kept high in order to use PWM.
SCL
PWM/SDA
Start Stop
t
REQ
PWM mode SMBus mode
>1.44ms
Figure 18: Switching from PWM mode to SMBus
8.6.2 Request condition
SCL
SMBus Request
t
REQ
>1,44ms
Figure 19: Request (switch to SMBus) condition
If PWM / Thermal relay is enabled, the MLX90614’s SMBus Request condition is needed to disable
PWM / Thermal relay and reconfigure PWM/SDA pin before starting SMBus communication. Once PWM /
Thermal relay is disabled, it can be only enabled by switching the supply OFF – ON or exit from Sleep Mode.
The MLX90614’s SMBus request condition requires forcing LOW the SCL pin for period longer than the request
time (t
REQ
>1,44ms). The SDA line value is ignored and is irrelevant in this case.
8.6.3 PWM is disabled
If PWM is disabled by means of EEPROM the PWM / SDA pin is directly used for the SMBus purposes
after POR. Request condition should not be sent in this case.