Datasheet

SNR=1.76dB+6.02dB ENOB´
(3)
H(z)=
1 z-
-OSR
1 z-
-1
(1+z )
- ´2
OSR
2
(4)
1 10 100 1000
OSR
ENOB(Bits)
16
14
12
10
8
6
4
2
0
Sincfast
Sinc
3
Sinc
Sinc
2
0 2 6 84 10
Settling Time(ms)
ENOB(Bits)
10
9
8
7
6
5
4
3
2
1
0
Sincfast
Sinc
3
Sinc
Sinc
2
ADS1204
SBAS301C – OCTOBER 2003 – REVISED FEBRUARY 2009 ........................................................................................................................................... www.ti.com
The effective number of bits (ENOB) can be used to protection, filter types other than Sinc
3
might be a
compare the performance of A/D converters and Δ Σ better choice. A simple example is a Sinc
2
filter.
modulators. Figure 33 shows the ENOB of the Figure 34 compares the settling time of different filter
ADS1204 with different filter types. In this data sheet, types. The Sincfast is a modified Sinc
2
filter as
the ENOB is calculated from the SNR as shown in Equation 4 shows:
Equation 3 :
Figure 33. Measured ENOB vs OSR
Figure 34. Measured ENOB vs Settling Time
In motor control applications, a very fast response
time for overcurrent detection is required. There is a
For more information, see application note SBAA094 ,
constraint between 1 µ s and 5 µ s with 3 bits to 7 bits
Combining the ADS1202 with an FPGA Digital Filter
resolution. The time for full settling is dependent on
for Current Measurement in Motor Control
the filter order. Therefore, the full settling of the Sinc
3
Applications, available for download at www.ti.com .
filter needs three data clocks and the Sinc
2
filter
needs two data clocks. The data clock is equal to the
modulator clock divided by the OSR. For overcurrent
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