cs5378 Cirrus Logic, Inc., cs5378 Datasheet - Page 60

• Manufacturer Part Number: cs5378
• Description: Low-power Single-channel Decimation Filter
• Manufacturer: Cirrus Logic, Inc.

17. TEST BIT STREAM GENERATOR
The CS5378 test bit stream (TBS) generator creates
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 inputs for
loopback testing of the digital filter.
17.1 Pin Descriptions
TBSDATA - Pin 8
Test bit stream 1-bit ∆Σ data output.
MCLK - Pin 11
Test bit stream clock output.
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.
The TBS input data from the digital filter is scaled
by the TBSGAIN register (0x2B). Maximum sta-
ble amplitude is 0x04FFFF, with 0x04B000 ap-
proximately full scale for the CS4373 test DAC.
The full scale 1-bit ∆Σ output from the TBS gener-
ator is defined as 25% minimum and 75% maxi-
mum one’s density.
DS639F1
Figure 36. Test Bit Stream Generator Block Diagram
Digital ∆Σ Modulator
TBSGAIN Register
Digital Filter
Data Bus
TBSDATA
17.3 TBS Configuration
Configuration options for the TBS generator are set
through the TBSCFG register (0x2A). Gain scal-
ing of the TBS generator output is set by the TB-
SGAIN register (0x2B).
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.
Output Rate - RATE[2:0]
Selects the TBSDATA output rate.
Synchronization - TSYNC
Enables synchronization of the TBS output phase
to the MSYNC signal.
Loopback - LOOP
Enables digital loopback from the TBS output to
the MDATA inputs.
1-bit
24-bit
24-bit
CS5378
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