MCP37231 datasheet(57/144 Pages) MICROCHIP

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DS20005322D-page 57

MCP37231/21-200 AND MCP37D31/21-200

FIGURE 4-15:

Simplified Block Diagram of Decimation Filters.

TABLE 4-13:

Control Parameter

Descriptions

Decimation Filter Settings

FIR_A<8:0>

0x7A, 0x7B

Channel A FIR configuration for single- or dual-channel mode

FIR_B<7:0>

0x7C

Channel B FIR configuration for single- or dual-channel mode

Output Data Rate and Clock Rate Settings(1)

OUT_DATARATE<3:0>

0x02

Output data rate: Equal to decimation rate

OUT_CLKRATE<3:0>

0x02

Output clock rate: Equal to decimation rate

Output Clock Phase Control Settings(2)

EN_PHDLY

0x64

Enable digital output phase delay when decimation filter is used

DCLK_PHDLY_DEC<2:0>

0x64

Digital output clock phase delay control

Digital Signal Post-Processing (DSPP) Function Block Settings

EN_DSPP_2 = 1

0x79

Enable dual-channel decimation

Note 1:

The output data and clock rates must be updated when decimation rates are changed.

Output clock (DCLK) phase control is used when the output clock is divided by OUT_CLKRATE<3:0>

bit settings.

Stage 1A

FIR

Input

DeMUX

Stage 2A

FIR

Stage 2B

FIR

Stage 3A

FIR

Stage 3B

FIR

Output

Single

Dual

Output

Dual

Stage 9A

FIR

Stage 9B

FIR

Output

D128

I/Q

Single

D512

Single

Ch. A

Ch. B

Single-channel operation

Single

(Note 1)

(Note 2)

(Note 3)

Ch.

Input

Dual

Ch.

Input

DeMUX

Ch. A

Ch. B

Input for DDC

MUX

DDC I/Q filtering

Output

D256

Dual

MUX

Note 1: Stage 1A FIR is the first stage of the FIR A filter.

2: (a) Single-channel mode: Only Channel A is used and controlled by FIR_A<8:0>.

(b) Dual-channel mode or I/Q filtering in DDC mode: Both Channel A and Channel B are used: Channel A is used for

the first channel or I data, and Channel B is used for the second channel or Q data.

3: Maximum decimation rate:

(a) When I/Q filtering in DDC mode is not used: 512x for single-channel and 256x for dual-channel mode.

(b) I/Q filtering in DDC mode: 128x each for FIR_A<8:1> and FIR_B<7:0>.

Dual-channel operation

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