CS5376A datasheet(64/107 Pages) CIRRUS

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CS5376A

17. TEST BIT STREAM GENERATOR

The CS5376A test bit stream (TBS) generator cre-

ates sine wave or impulse

∆Σ bit stream data to

drive an external test DAC. The TBS digital output

can also be internally connected to the MDATA in-

puts for loopback testing of the digital filter.

17.1 Pin Descriptions

TBSDATA - Pin 9

Test bit stream 1-bit

∆Σ data output.

TBSCLK - Pin 8

Test bit stream clock output. Not used by the

CS4373 test DAC.

17.2 TBS Architecture

The test bit stream generator consists of a data in-

terpolator and a digital

∆Σ modulator. It receives

periodic 24-bit data from the digital filter to create

a 1-bit

∆Σ data output on the TBSDATA pin. It also

creates a clock signal at the data rate, output to the

TBSCLK pin.

The TBS input data from the digital filter is scaled

by the TBSGAIN register (0x2B). Maximum stable

amplitude is 0x04FFFF, with 0x04B000 approxi-

mately full scale for the CS4373 test DAC. The full

scale 1-bit

∆Σ output from the TBS generator is de-

fined as 25% minimum and 75% maximum one’s

density.

17.3 TBS Configuration

Configuration options for the TBS generator are set

through the TBSCFG register (0x2A). Gain scaling

of the TBS generator output is set by the TBSGAIN

Interpolation Factor - INTP[7:0]

Selects how many times the interpolator uses a data

point when generating the output bit stream. Inter-

polation is zero based and represents one greater

than the programmed register value.

Operational Mode - TMODE

Selects between sine wave or impulse output mode.

Clock Rate - RATE[2:0]

Selects the TBSDATA and TBSCLK output rate.

Synchronization - TSYNC

Enables synchronization of the TBS output phase

to the MSYNC signal.

Digital

∆Σ Modulator

24-bit

1-bit

TBSDATA

Digital Filter

TBSGAIN Register

24-bit

Figure 36. Test Bit Stream Generator Block Diagram

Data Bus

TBSCLK

Clock Generation

TBSCFG Register

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