Datasheet
ENOB(bits)
SettlingTime( s)m
0
4
8 10
8
7
6
5
4
3
2
1
0
2
6
9
10
Sinc
1
Sinc
2
Sinc
3
ADS1203
Sincfast
Group_Delay + Order_of_Filter @
OSR
f
MODULATOR
(12)
OSR +
Group_Delay @ f
MODULATOR
Order_of_Filter
+
3.2ms @ 10MHz
2
+ 16
(13)
Hall Sensor Measurement
AMC1210
SBAS372D – APRIL 2006 – REVISED MAY 2009 ..............................................................................................................................................................
www.ti.com
Figure 28. Effective Number of Bits vs Settling Time (ADS1203)
The user should choose a digital filter that gives the maximum ENOB for the desired settling time. If a 3.2 µ s
settling time is assumed, the user should select a Sinc
2
filter. For any delay greater than 4 µ s, the user should
choose a Sinc
3
filter.
The total delay can be represented by Equation 12 :
We can then calculate what OSR is necessary to achieve a delay time of 3.2 µ s by using Equation 13 .
A Sinc
2
comparator filter with an OSR of 16 satisfies the settling time requirements for this example system. A
high and low comparator value can be chosen by referring to Table 9 . For the present example, the comparator
filter is capable of a span of 256 codes (from 0 to 256). If an over-current situation is defined at ± 25% of the
modulator full-scale range, the High Level Threshold level (HLT15 – 0) and Low Level Threshold level (LLT15 – 0)
should be set to a maximum value of 64 from the full-scale values, or 64 to 192. It may also be necessary to
lower this value to avoid an accidental over-current situation. If a 5% guardband is presumed, the threshold
levels should be set to 60 and 196.
The AMC1210 can be used directly with the ADS120x family of modulators to interface with Hall sensors in order
to provide magnetic field strength measurements. The ADS1208 is a 16-bit, second order, delta-sigma modulator
with Hall element biasing circuitry. By connecting the MCLK and MDATA lines of the ADS1208 to the INx and
CLKx lines, the AMC1210 needs only a system clock to provide filtered data from the modulator.
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