mlx90615 Melexis Company, mlx90615 Datasheet - Page 17

• Manufacturer Part Number: mlx90615
• Description: Infra Red Thermometer
• Manufacturer: Melexis Company

8.6 PWM
The MLX90615 can be read via PWM or SMBus compatible interface. Selection of PWM output is done in
EEPROM configuration (factory default is SMBus). Object or ambient temperature can be read through PWM.
The PWM period is derived from the on-chip oscillator and is programmable in a low or high frequency.
Temperature ranges for the PWM output are written in EEPROM 0x0, 0x1 – PWM Tmin and PWM Trange
(Tmax-Tmin), scale is 0.02°K/LSB. Note that in SMBus mode the EEPROM 0x0 is used for Slave address
SA.
8.6.1 PWM format
The temperature reading can be calculated from the signal timing as:
where Tmin and Trange are the corresponding rescale coefficients in EEPROM for the selected temperature
output and T is the PWM period. Tout is To or Ta according to bit Config Register, 2.
The different time intervals t
t
t
t
static, allowing detection of fault on the line (disconnected device, short on the line).
Example:
T
To
To
Captured PWM high duration is 0.495*T => t
measured object temperature = 2X0.370* (50°C -0°C)+0°C = +37.0°C.
3901090615
Rev 001
1
2
3
o
: Start buffer. During this time the signal is always high. t
: Valid Data Output Band, 0 to 1/2T. PWM output data resolution is 10 bit.
: Low time. The maximum duty cycle is limited to t
min
max
=> Config Reg,2 = 0
= 0°C
= To
min
+ T
range
= +50°C
Config Register[2:0]
1
, t
2
and t
=>
=>
000
010
100
110
xx1
3
Tout
have the following functions:
PWM T
PWM T
2
=(0.495 – 0.125)*T=0.370*T =>
Figure 14: PWM format
=
⎡
⎢ ⎣
min
range
Page 17 of 30
2
T
t
2
[EEPROM] = 50 * (to
1
[EEPROM] = 50 * (to
*
+ t
Trange
2
= 0.625 This means that the PWM line will never go
1
PWM data
= 0.125*T (T is the PWM period, refer to fig. 14).
⎤
⎥ ⎦
To
To
Ta
Ta
+
SMBus, PWM disabled
Tmin
min
range
,
+ 273.15) = 355Bh
) = 09C3h
PWM frequency
Infra Red Thermometer
High
High
Low
Low
MLX90615
Data Sheet
28/Aug/2008