21 / 35 page
MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
3901090614
Page 21 of 35
Data Sheet
Rev 1.0
14/Sep/2006
7.6 Switching Between PWM and SMBus communication
7.6.1 PWM is enabled
The diagram below illustrates the way of switching to SMBus if PWM is enabled (factory programmed POR
default for MLX90614 is SMBus, PWM enabled). Note that the SCL pin needs to be kept high in order to use
PWM.
Figure 13: Switching from PWM mode to SMBus
7.6.2 Request condition
Figure 14: Request (switch to SMBus) condition
If PWM is enabled, the MLX90614’s SMBus Request condition is needed to disable PWM and reconfigure
PWM/SDA pin before starting SMBus communication. Once disabled PWM, it can be only enabled by
switching Off-On of the supply or exit from Sleep Mode. The MLX90614’s SMBus request condition requires
forcing LOW the SCL pin for period longer than the request time (tREQ). The SDA line value is ignored in this
case.
7.6.3 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.
SCL
PWM/SDA
Start
Stop
t
REQ
PWM
SMBus
SCL
SMBus Request
tREQ
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