AD7147A Analog Devices, AD7147A Datasheet - Page 21

• Manufacturer Part Number: AD7147A
• Manufacturer: Analog Devices

Specifications of AD7147A

• Resolution (bits): 16bit
• # Chan: 13
• Sample Rate: 111SPS
• Interface: I²C/Ser 2-Wire,Ser,SPI
• Analog Input Type: Capacitive
• Ain Range: ± 8 pF (Delta C)
• Adc Architecture: Sigma-Delta
• Pkg Type: CSP

FF_SKIP_CNT
The proximity detection fast FIFO is used by the on-chip logic
to determine if proximity is detected. The fast FIFO expects to
receive samples from the converter at a set rate. The fast filter
skip control, FF_SKIP_CNT (Bits[3:0], Address 0x002), is used
to normalize the frequency of the samples going into the FIFO,
regardless of how many conversion stages are in a sequence.
This value determines which CDC samples are not used
(skipped) by the proximity detection fast FIFO.
Table 14. FF_SKIP_CNT Settings
FF_SKIP
_CNT
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Decimation = 64
0.768 × (SEQUENCE_STAGE_NUM + 1) ms
1.536 × (SEQUENCE_STAGE_NUM + 1) ms
2.304 × (SEQUENCE_STAGE_NUM + 1) ms
3.072 × (SEQUENCE_STAGE_NUM + 1) ms
3.84 × (SEQUENCE_STAGE_NUM + 1) ms
4.608 × (SEQUENCE_STAGE_NUM + 1) ms
5.376 × (SEQUENCE_STAGE_NUM + 1) ms
6.144 × (SEQUENCE_STAGE_NUM + 1) ms
6.912 × (SEQUENCE_STAGE_NUM + 1) ms
7.68 × (SEQUENCE_STAGE_NUM + 1) ms
8.448 × (SEQUENCE_STAGE_NUM + 1) ms
9.216 × (SEQUENCE_STAGE_NUM + 1) ms
9.984 × (SEQUENCE_STAGE_NUM + 1) ms
10.752 × (SEQUENCE_STAGE_NUM + 1) ms
11.52 × (SEQUENCE_STAGE_NUM + 1) ms
12.288 × (SEQUENCE_STAGE_NUM + 1) ms
Decimation = 128
1.536 × (SEQUENCE_STAGE_NUM + 1) ms
3.072 × (SEQUENCE_STAGE_NUM + 1) ms
4.608 × (SEQUENCE_STAGE_NUM + 1) ms
6.144 × (SEQUENCE_STAGE_NUM + 1) ms
7.68 × (SEQUENCE_STAGE_NUM + 1) ms
9.216 × (SEQUENCE_STAGE_NUM + 1) ms
10.752 × (SEQUENCE_STAGE_NUM + 1) ms
12.288 × (SEQUENCE_STAGE_NUM + 1) ms
13.824 × (SEQUENCE_STAGE_NUM + 1) ms
15.36 × (SEQUENCE_STAGE_NUM + 1) ms
16.896 × (SEQUENCE_STAGE_NUM + 1) ms
18.432 × (SEQUENCE_STAGE_NUM + 1) ms
19.968 × (SEQUENCE_STAGE_NUM + 1) ms
21.504 × (SEQUENCE_STAGE_NUM + 1) ms
23.04 × (SEQUENCE_STAGE_NUM + 1) ms
24.576 × (SEQUENCE_STAGE_NUM + 1) ms
Rev. B | Page 21 of 68
FAST FIFO Update Rate
Determining the FF_SKIP_CNT value is required only once
during the initial setup of the capacitance sensor interface.
Table 13 shows how FF_SKIP_CNT controls the update rate of
the fast FIFO. The recommended value for the setting when
using all 12 conversion stages on the AD7147A is 0000, or no
samples skipped.
Decimation = 256
3.072 × (SEQUENCE_STAGE_NUM + 1) ms
6.144 × (SEQUENCE_STAGE_NUM + 1) ms
9.216 × (SEQUENCE_STAGE_NUM + 1) ms
12.288 × (SEQUENCE_STAGE_NUM + 1) ms
15.36 × (SEQUENCE_STAGE_NUM + 1) ms
18.432 × (SEQUENCE_STAGE_NUM + 1) ms
21.504 × (SEQUENCE_STAGE_NUM + 1) ms
24.576 × (SEQUENCE_STAGE_NUM + 1) ms
27.648 × (SEQUENCE_STAGE_NUM + 1) ms
30.72 × (SEQUENCE_STAGE_NUM + 1) ms
33.792 × (SEQUENCE_STAGE_NUM + 1) ms
36.864 × (SEQUENCE_STAGE_NUM + 1) ms
39.936 × (SEQUENCE_STAGE_NUM + 1) ms
43.008 × (SEQUENCE_STAGE_NUM + 1) ms
46.08 × (SEQUENCE_STAGE_NUM + 1) ms
49.152 × (SEQUENCE_STAGE_NUM + 1) ms
AD7147A