CS5376A datasheet(66/107 Pages) CIRRUS

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CS5376A

Custom TBS Data

If a required test frequency cannot be generated us-

ing the on-chip test bit stream data, a custom data

set can be written into the CS5376A. The number

of data points to write, up to a maximum of 1024,

depends on the required test signal frequency, out-

put rate, and available interpolation factors. Cus-

tom data sets must be continuous on the ends; i.e.

when copied end-to-end the data set must produce

a smooth curve.

17.5 TBS Sine Wave Output

When the TMODE bit in the TBSCFG register is

low, the TBS generator operates in sine wave

mode. In this mode, sine wave data from digital fil-

ter memory is used to create a sine wave test signal

that can drive a test DAC. Sine wave frequency and

output data rate are calculated as shown by the

characteristic equation of Table 16.

The sine wave maximum

∆Σ one’s density output

from the TBS generator is set by the TBSGAIN

maximum of 0x04FFFF, with the TBS generator

unstable for higher amplitudes. For the CS4373 test

DAC, a gain value of 0x04B000 produces an ap-

proximately full scale sine wave output (5 Vpp dif-

ferential).

17.6 TBS Impulse Output

If the TMODE bit in TBSCFG is set high, the TBS

generator operates in impulse mode. In this mode,

the value in TBSGAIN sets the amplitude of the

generated impulse. Impulse amplitude and period

are calculated as shown in Table 17.

To create an impulse from the TBS generator, the

TBSGAIN register should be set to maximum,

0x04FFFF, and the INTP bits in TBSCFG should

also be set to maximum, 0xFF. The RATE bits

should be set to produce data at the correct rate for

the selected test DAC.

A rising edge on the TIMEB pin triggers the im-

pulse output. When impulse mode is enabled but no

TIMEB input is received, the TBS generator uses a

negated TBSGAIN register as a repetitive input

value. When a rising edge is recognized on the

TIMEB pin, a single positive TBSGAIN value is

written to the TBS generator to create the impulse.

17.7 TBS Loopback Testing

Included as part of the CS5376A test bit stream

generator is a feedback path to the digital filter

MDATA inputs. This loopback mode provides a

fully digital signal path to test the TBS generator,

digital filter, and data collection interface. Digital

Test Bit Stream Impulse Characteristics:

Interpolation

Selection

(INTP)

Output Rate

Selection

(RATE)

Pulse Width

from CS4373

Gain Scale

Factor

(TBSGAIN)

Pulse Height

from CS4373

0xFF

0x5

500

µs

0x04B000

860 mV

0xFF

0x4

1 ms

0x04B000

820 mV

0xFF

0x3

2 ms

0x04B000

820 mV

0x7F

0x5

250

µs

0x04B000

820 mV

0x7F

0x4

500

µs

0x04B000

820 mV

0x7F

0x3

1 ms

0x04B000

820 mV

Table 17. TBS Impulse Characteristics

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