MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
8.5 PWM
The MLX90614 can be read via PWM or SMBus compatible interface. Selection of PWM output is done in
EEPROM configuration (factory default is SMBus). PWM output has two programmable formats, single and
dual data transmission, providing single wire reading of two temperatures (dual zone object or object and
ambient). The PWM period is derived from the on-chip oscillator and is programmable.
Config Register[5:4] PWM1 data PWM2 data
Tmin,1
Tarange,L
Tarange,L
Tomin
Tmax,1
Tarange,H
Tarange,H
Tomax
Tmin,2
Tomin
Tomin
Tomin
N.A.
Tmax,2
Tomax
Tomax
Tomax
N.A.
00
01
Ta
Ta
Tobj1
Tobj2
11
10*
Tobj1
Tobj2
Tobj2
Undefined
Tomin
Tomax
Note: Serial data functions (2-wire / PWM) are multiplexed with a thermal relay function (described in the
“Thermal relay” section).
* not recommended for extended PWM format operation
T
T
T
T
t1
t2
t3
Single PWM output format (4 periods)
2T, data 1 transmission
t3
2T, data 2 transmission
t1
t4
t5
t2
Extended PWM output format
Start buffer
Data band
Error signaling band
End buffer
Figure 11: PWM timing
8.5.1 Single PWM format
In single PWM output mode the settings for PWM1 data only are used. The temperature reading can be
calculated from the signal timing as:
2t
⎡
⎣
⎤
⎦
2
Tout =
*
(
Tmax − Tmin + Tmin ,
)
⎢
⎥
T
where Tmin and Tmax are the corresponding rescale coefficients in EEPROM for the selected temperature
output (Ta, object temperature range is valid for both Tobj1 and Tobj2 as specified in the previous table) and
T is the PWM period. Tout is Tobj1, Tobj2 or Ta according to Config Register [5:4] settings.
3901090614
Rev 003
Page 18 of 40
Data Sheet
03/Oct/2007
MELEXIS [ Melexis Microelectronic Systems ]
