MLX90614 datasheet(21/35 Pages) ETC2

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

REQ

PWM

SMBus

SCL

SMBus Request

tREQ

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