AS5510 AppNote Noise Reduction

Application Note – AN5510-10 Noise Reduction
AS5510
10-bit Linear Incremental Position
Sensor with Digital Angle output
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Revision 1.0 / 2013/01/30
AN5510-10 Noise Reduction
Table of Contents
1.
General Description ............................................................................................................... 2
2.
Input Related Noise ............................................................................................................... 2
3.
On Chip Noise Reduction ...................................................................................................... 3
4.
External Noise Reduction ...................................................................................................... 3
5.
Ordering Information .............................................................................................................. 5
Copyright ....................................................................................................................................... 6
Disclaimer ..................................................................................................................................... 6
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AN5510-10 Noise Reduction
1. General Description
The AS5510 is a linear Hall sensor with 10 bit resolution and I²C interface. It can measure
absolute position of lateral movement of a simple 2-pole magnet. The typical arrangement is
shown below in Figure 1.
Figure 1:
Linear Position Sensor AS5510 + Magnet
magnet
N
S
AS5510
PCB
Depending on the magnet size, a lateral stroke of 0.5~2mm can be measured with air gaps
around 1.0mm. To conserve power, the AS5510 may be switched to a power down state when it
is not used.
Find more information on our webpage:
https://www.ams.com/eng/Products/Magnetic-Position-Sensors/Linear-Incremental-MagneticPosition-Sensors/AS5510
2. Input Related Noise
Input related noise is given in the datasheet of the AS5510 and in Table 1 below. Depending on
the selcted sensitivity option and on the sampling frequency this noise leads to a signal jitter at
the output and is shown in Table 2
Table 1:
AS5510 Input related noise
Mode
fs
tdelay
Maximum Noise (Equivalent to 8*rms)
Fast (default)
50 KHz
20 µs
0.8 mTpp
Slow
12.5 KHz
50 µs
0.5 mTpp
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AN5510-10 Noise Reduction
Table 2:
AS5510 Output jitter
Sensitivity
Step Size
Max. Fast Mode Jitter
Max.Slow Mode Jitter
+/- 50 mT
96.66 µT/LSB
9 LSB
6 LSB
+/- 25 mT
48.83 µT/LSB
17 LSB
11 LSB
+/- 12.5 mT
24.41 µT/LSB
35 LSB
22 LSB
+/- 18.75 mT
36.62 µT/LSB
22 LSB
14 LSB
3. On Chip Noise Reduction
In some applications it may be nessecary to activate the slow mode to reduce the jitter at the
outputs. The AS5510 offers the option to switch to a slow mode that lowers the sampling
frequency to decrease the output jitter.
The Slow Mode is activated by setting the bit 2 (Fast / Slow mode) of register 02h in the AS5510
control register.
Example:
I2C_Write8(0x56, 0x02, 0x04); // Slow Mode
4. External Noise Reduction
If the application should require less jitter than offered by the slow mode, an external averageing
will reduce the jitter to the desired noise level.
In the best case situation the noise reduces with the square root of the number of samples.
Example:
𝑅𝑒𝑑𝑢𝑐𝑖𝑛𝑔 𝑁𝑜𝑖𝑠𝑒 𝑓𝑟𝑜𝑚 0.5𝑚𝑇𝑝𝑝 𝑡𝑜 0.05𝑚𝑇𝑝𝑝; 𝐼𝑚𝑝𝑟𝑜𝑣𝑒𝑚𝑒𝑛𝑡 𝑓𝑎𝑐𝑡𝑜𝑟 10
𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑠𝑎𝑚𝑝𝑙𝑒𝑠 = 102 = 100
𝑓𝑎𝑣𝑔 =
𝑇𝑎𝑣𝑔 =
12500 𝐻𝑧
= 125 𝐻𝑧
100
1
𝑓𝑎𝑣𝑔
= 8𝑚𝑠
Equation 1:
Number of Samples
Equation 2:
Frequency Averaged Output
2
𝑁𝑜𝑖𝑠𝑒
𝑆𝑎𝑚𝑝𝑙𝑒𝑠 = (
)
𝐷𝑒𝑠𝑖𝑟𝑒𝑑 𝑁𝑜𝑖𝑠𝑒
𝑓𝑎𝑣𝑔 =
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𝑓𝑠
𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑆𝑎𝑚𝑝𝑙𝑒𝑠
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AN5510-10 Noise Reduction
Example:
#define average 100
for (count = average; count; count--)
{
Data1 = I2C_Read8(I2C_ADDR, 0x00);
Data2 = I2C_Read8(I2C_ADDR, 0x01);
position += ((Data2 & 0x03)<<8) + Data1;
}
position = position / average;
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AN5510-10 Noise Reduction
5. Ordering Information
Table 3:
Ordering Information
Ordering Code
Description
comments
AS5510-AB
AS5510 Adapterboard
For rapid evaluation and prototyping
AS5510-DB
AS5510 Demoboard
For functional demonstration
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AN5510-10 Noise Reduction
Copyright
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Term of Sale. ams AG makes no warranty, express, statutory, implied, or by description regarding the
information set forth herein or regarding the freedom of the described devices from patent infringement. ams
AG reserves the right to change specifications and prices at any time and without notice. Therefore, prior to
designing this product into a system, it is necessary to check with ams AG for current information.
This product is intended for use in normal commercial applications. Applications requiring extended
temperature range, unusual environmental requirements, or high reliability applications, such as military,
medical life-support or lifesustaining equipment are specifically not recommended without additional
processing by ams AG for each application. For shipments of less than 100 parts the manufacturing flow might
show deviations from the standard production flow, such as test flow or test location.
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