MLX90251 Datasheet, PDF (8/22 Pages) Melexis Microelectronic Systems – Programmable Linear Hall Effect Sensor

MLX90251
Programmable Linear Hall Effect Sensor
10.1 Output Quiescent Voltage (V_OQ)
Two parameters, AGND and OFFSET, are used for adjustment of the V_OQ. The AGND is a 10 bit parameter
for coarse adjustment of V_OQ. It has a resolution of approximately 0.014V and a range of -100%V_DD to
200%V_DD. The OFFSET is a 10 bit parameter with a resolution of approximately -0.005V. The OFFSET
parameter is used for fine adjustment of the V_OQ, while the AGND parameter is used to set the range. The
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_OQ.
V_OQ
=
−0.75V
+


14.25V
1023
∗
AGND

+


−
5.0V
1023
∗
OFFSET


V_DD =5.00V
This formula approximates the typical V_OQ of the MLX90251. The actual V_OQ formula varies slightly from chip
to chip. Melexis calibrates the AGND setting during final test so that the V_OQ is approximately 50%V_DD with
OFFSET set to 512. This gives the V_OQ a range of 0%V_DD to 100%V_DD without adjusting the AGND value.
The OFFSET parameter is often used to set the offset in the application's output transfer characteristic.
10.2 Thermal V_OQ Drift (DRIFT)
The Thermal V_OQ 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 V_OQ 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 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.
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: MLX90251 Rough Gain Small Signal Amplifier Gain
3901090251
Rev 009
Page 8 of 22
Data Sheet
Nov/06