MLX90313 データシートの表示（PDF） - Melexis Microelectronic Systems
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MLX90313 Datasheet PDF : 35 Pages
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MLX90313
Programmable IR Sensor Interface
* This option is available only if ENLN=1
The pin ENLN controls both the noise level and distortion of the amplifier. If ENLN=1 the noise of the
amplifier is 23nVrms/√Hz, the gain of 20 in first stage is available but the input signal must be less than 4
mV for less than 0.05% full scale distortion.
If ENLN is 0 then the span of the input signal can be ± 40mV with distortion less than 0.1% full scale. In
this case the noise floor of the amplification chain increases 3 times.
Temp-amplifier chain
MLX90313 is available with gain settings for the Temp-amplifier ranging from 5 to 50. The gain can be
selected by setting the appropriate bits of the ‘Temp gain and current control’-register (EEPROM address
02h) according to the table below. Any gain between the abovementioned limits can be obtained within an
accuracy of ±6.5%. It is also possible to completely bypass the temperature amplifier and force the input
signal directly to the ADC. The amplifier input-referred white noise level is below 400nVrms/√Hz.
The common mode input range of the amplifier is –100mV to VDD-3V. The output range of the amplifier is
0V to VDD-0.2V. The output of the amplifier is referred to the potential on AGND.
Temp chain gain settings
GT = G pr × Gl × M
stage G pr
Gl
M
contr.
bits
GCT2 GCT1 GCT0
GCT5 GCT4 GCT3
IRSEL2 IRSEL1 IRSEL0
0
0
0
1
X
X
X
0
1
1
5
0
0
0
0
0
1
1.067 0
1.143 0
0
0
0
1
off
1/7
1
0
0
10
0
1
0
1.231 0
1
0
2/7
settin 1
0
1
15
0
1
1
1.333 0
1
1
3/7
g
1
1
0
20
1
1
0
0
0
1
1.455 1
1.600 1
0
0
0
1
4/7
5/7
1
1
1
25
1
1
0
1.778 1
1
0
6/7
1
1
1
2.000 1
1
1
1
Note: When the current mirror is on (all settings except IRSEL[2:0] = 000b) the gain is defined as follows:
GT
=
Vout
Rsens ⋅ Icref
where Vout is the output of the analog amplifier chain, Rsens is the resistance of the sensor connected between
TINP and TINN and Icref is the current out of CREF.
When the current mirror is off (IRSEL[2:0]=000b), M should be replaced by 1 and the gain is defined as follows:
GT
= Vout
Vin
where Vin is the voltage difference between TINP and TINN
If GCT[2:0]=0 then the temp chain will be completely off, the Timp pin will be connected directly to the ADC input,
providing Gain=1
Current Reference
The thermistor (or sensor) connected to TINP must be biased with a current source. This bias current is
mirrored from the current through the external resistor between CREF and VSS. The voltage maintained
at the CREF pin is derived from internal band-gap voltage, and thus constant. The typical value of the
voltage at CREF pin is 2V.
The current mirror ratio can be set between 1/7 and 1 according to the table for the Temp-chain gain
settings. The setting with IRSEL[2:0]=000b switches the current mirror off. In this case the thermistor
must be biased by external circuitry.
MLX90313 Programmable IR sensor Interface Page 10
3901090313
Rev 1.0 21-July-2001
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