CS5378(2005) View Datasheet(PDF) - Cirrus Logic

Part Name

Description

MFG CO.

CS5378
(Rev.:2005)

Low-power Single-channel Decimation Filter

Cirrus Logic 

CS5378

Bits

23:20

19:16

15:12

11:8

Selection

0000

0000

IIR2

IIR1

7:4

FIR2

3:0

FIR1

Bits 15:12

0000

0001

0010

0011

0100

IIR2 Coefficients

3 Hz @ 2000 SPS

3 Hz @ 1000 SPS

3 Hz @ 500 SPS

3 Hz @ 333 SPS

3 Hz @ 250 SPS

Bits 11:8

0000

0001

0010

0011

0100

IIR1 Coefficients

3 Hz @ 2000 SPS

3 Hz @ 1000 SPS

3 Hz @ 500 SPS

3 Hz @ 333 SPS

3 Hz @ 250 SPS

Bits 3:0

0000

0001

FIR1 Coefficients

Linear Phase

Minimum Phase

Bits 7:4

0000

0001

FIR2 Coefficients

Linear Phase

Minimum Phase

Figure 22. FIR and IIR Coefficient Set Selection Word

11.2.2 Output Word Rate

The CS5378 digital filter supports output word

rates (OWRs) between 4000 SPS and 1 SPS. The

output word rate is selected by the DEC bits in the

FILTCFG register.

When taking data directly from the SINC filter, the

decimation of the FIR1 and FIR2 stages is by-

passed and the actual output word rate is multiplied

by a factor of eight compared with the register se-

lection. When taking data directly from FIR1, the

decimation of the FIR2 stage is bypassed and the

actual output word rate is multiplied by a factor of

two. Data taken from the FIR2, IIR1, IIR2, or IIR3

filtering stages is output at the selected rate.

11.2.3 Digital Filter Clock

The digital filter clock rate is programmable be-

tween 8.192 MHz and 32 kHz by bits in the CON-

FIG register.

Computation Cycles

The minimum digital filter clock rate for a config-

uration depends on the computation cycles required

to complete digital filter convolutions at the select-

ed output word rate. All configurations work for a

maximum digital filter clock, but lower clock rates

consume less power.

Standby Mode

The CS5378 can be placed in a low-power standby

mode by sending the ‘Filter Stop’ configuration

command and programming the digital filter clock

to 32 kHz. In this mode the digital filter idles, con-

suming minimal power until re-enabled by later

configuration commands.

DS639F1

39

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