ADIS16136/PCBZ AD [Analog Devices], ADIS16136/PCBZ Datasheet - Page 11

• Manufacturer Part Number: ADIS16136/PCBZ
• Manufacturer: AD [Analog Devices]

Data Sheet
DIGITAL PROCESSING CONFIGURATION
Figure 18 provides a block diagram for the sampling and digital
filter stages inside the ADIS16136. Table 15 provides a summary
of registers for sample rate and filter control.
Table 15. Digital Processing Registers
Register Name
SMPL_PRD
AVG_CNT
DEC_RATE
INTERNAL SAMPLE RATE
The SMPL_PRD register in Table 16 provides a programmable
control for the internal sample rate. Use the following formula
to calculate the decimal number for the code to write into this
register:
The factory default setting for SMPL_PRD sets the internal
sample rate to a rate of 1024 SPS; the minimum setting for the
SMPL_PRD register is 0x000F, which results in an internal
sample rate of 2048 SPS.
Table 16. SMPL_PRD Bit Descriptions
Bits
[15:0]
SMPL
Description (Default = 0x001F)
Clock setting bits; sets f
_
PRD
Address
0x1E
0x20
0x22
=
32
( )
,
f
768
S
−
; 1
Description
Sample rate control
Digital filtering and range control
Decimation rate setting
f
S
S
≤ 2048 SPS
in Figure 18
Rev. A | Page 11 of 20
INPUT CLOCK CONFIGURATION
Set SMPL_PRD = 0x0000 (DIN = 0x9F00, then DIN = 0x9E00)
to disable the internal clock and enable DIO4/CLKIN as a clock
input pin.
DIGITAL FILTERING
The AVG_CNT register (see Table 17) provides user controls
for the low-pass filter. This filter contains two cascaded averaging
filters that provide a Bartlett window FIR filter response (see
Figure 18). For example, set AVG_CNT[7:0] = 0x04 (DIN =
0xA004) to set each stage to 16 taps. When used with the default
sample rate of 1024 SPS, this establishes a −3 dB bandwidth of
approximately 24 Hz for this filter.
Table 17. AVG_CNT Bit Descriptions
Bits
[15:3]
[2:0]
–100
–120
–140
–20
–40
–60
–80
0.001
Figure 17. Bartlett Window FIR Filter Frequency Response
0
Description (Default = 0x0000)
Don’t care
Binary; B variable in Figure 18; maximum = 110 (6)
N = 2
N = 4
N = 16
N = 64
0.01
FREQUENCY (
f
/
f
S
)
0.1
ADIS16136
1