mlx90251 Melexis Company, mlx90251 Datasheet - Page 8

• Manufacturer Part Number: mlx90251
• Description: Programmable Linear Hall Effect Sensor
• Manufacturer: Melexis Company

Two parameters, AGND and OFFSET, are used for adjustment of the V
for coarse adjustment of V
200%V
parameter is used for fine adjustment of the V
large adjustable range allows the MLX90251 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
V
This formula approximates the typical V
to chip. Melexis calibrates the AGND setting during final test so that the V
OFFSET set to 512. This gives the V
The OFFSET parameter is often used to set the offset in the application's output transfer characteristic.
The Thermal V
during final test. The value is set to achieve a V
150°C. This parameter is not used by the end customer.
The Sensitivity of the MLX90251 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 the theoretical 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.
Table 8: MLX90251 Rough Gain Small Signal Amplifier Gain
3901090251
Rev 009
Rough Gain (MSB LSB)
OQ
10.1 Output Quiescent Voltage (V
10.2 Thermal V
10.3 Sensitivity, Rough Gain and Fine Gain
.
DD
V
. The OFFSET is a 10 bit parameter with a resolution of approximately -0.005V. The OFFSET
00 (00 00)
01 (00 01)
02 (00 10)
03 (00 11)
04 (01 00)
05 (01 01)
06 (01 10)
07 (01 11)
08 (10 00)
09 (10 01)
10 (10 10)
11 (10 11)
12 (11 00)
13 (11 01)
14 (11 10)
15 (11 11)
OQ
=
OQ
−
. 0
Drift is tuned using 4 bits. This parameter, DRIFT, is calibrated for each unit by Melexis
75
OQ
V
+
Drift (DRIFT)



OQ
14
. It has a resolution of approximately 0.014V and a range of -100%V
1023
DIDO
.
25
V
205
205
205
205
16
16
16
16
39
39
39
39
82
82
82
82
∗
OQ
AGND
OQ
a range of 0%V
of the MLX90251. The actual V
DTS
OQ



OQ
+
2.33
2.33
2.33
2.33
)
OQ
1.0
1.5
4.0
1.0
1.5
4.0
1.0
1.5
4.0
1.0
1.5
4.0
, while the AGND parameter is used to set the range. The
Page 8 of 22
Programmable Linear Hall Effect Sensor



accuracy below 10mV over a temperature span of 25° C to
−
1023
5
0 .
V
DD
Gain
∗
to 100%V
OFFSET
156
123
191
328
205
308
477
820
16
24
37
64
39
59
91
82
DD



without adjusting the AGND value.
OQ
V
DD
. The AGND is a 10 bit parameter
OQ
OQ
=
. 5
00
is approximately 50%V
formula varies slightly from chip
V
MLX90251
Data Sheet
Nov/06
DD
DD
to
with