MLX90277 Просмотр технического описания (PDF) - Melexis Microelectronic Systems
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MLX90277 Datasheet PDF : 21 Pages
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MLX90277
Dual Programmable Linear Hall Effect Sensor
10.1 Output Quiescent Voltage (VOQ)
Two parameters, AGND and OFFSET, are used for adjustment of the VOQ. The AGND is a 10 bit parameter
for coarse adjustment of VOQ. It has a resolution of approximately 0.014V and a range of -100%VDD to
200%VDD. The OFFSET is a 10 bit parameter with a resolution of approximately -0.005V. The OFFSET
parameter is used for fine adjustment of the VOQ, while the AGND parameter is used to set the range. The
large adjustable range allows the MLX90277 to be used in an unipolar magnetic system without limiting the
output voltage span. The formula below shows how the AGND and OFFSET parameters combine to set the
VOQ.
VOQ
=
−0.75V
+
14.25V
1023
∗
AGND
+
−
5.0V
1023
∗
OFFSET
VDD =5.00V
This formula approximates the typical VOQ of the MLX90277's individual sensors. The actual VOQ formula
varies slightly from IC to IC. Melexis calibrates the AGND setting during final test so that the VOQ is
approximately 50%VDD with OFFSET set to 512. This gives the VOQ a range of 0%VDD to 100%VDD without
adjusting the AGND value. The OFFSET parameter is often used to set the application's offset output
transfer characteristic.
10.2 Thermal VOQ Drift (DRIFT)
The Thermal VOQ Drift is tuned using 4 bits. This parameter, DRIFT, is calibrated for each unit by Melexis
during final test. The value is set to achieve a VOQ accuracy below 10mV over a temperature span of 25°C to
150°C. This parameter is not used by the end customer.
10.3 Sensitivity, Rough Gain and Fine Gain
The Sensitivity of the MLX90277's individual sensors is controlled through parameters linked to dedicated
internal amplification stages. The parameter Rough Gain (RG), or pre-amplifier, has 4 bits for adjustment of
two stages. The two MSB affect the Differential Input Differential Output (DIDO) stage. The two LSB effect
the Differential to Single output (DTS) stage. The gain of both the DIDO and DTS are multiplied to get the
total RG. The table below shows typical values of the small signal amplifier gain vs. the parameter RG. The
pre-amplifier is chopper stabilized and the refresh frequency is adapted automatically to the RG setting to
match the chopper gain-bandwidth product.
Rough Gain (MSB LSB) DIDO
DTS
Gain
00 (00 00)
16
1.0
16
01 (00 01)
16
1.5
24
02 (00 10)
16
2.33
37
03 (00 11)
16
4.0
64
04 (01 00)
39
1.0
39
05 (01 01)
39
1.5
59
06 (01 10)
39
2.33
91
07 (01 11)
39
4.0
156
08 (10 00)
82
1.0
82
09 (10 01)
82
1.5
123
10 (10 10)
82
2.33
191
11 (10 11)
82
4.0
328
12 (11 00)
205
1.0
205
13 (11 01)
205
1.5
308
14 (11 10)
205
2.33
477
15 (11 11)
205
4.0
820
Table 8: MLX90277 Rough Gain Small Signal Amplifier Gain
3901090277
Rev 004
Page 8 of 21
Data Sheet
Nov/06
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