THS4532_16 Datasheet, PDF (39/58 Pages) Texas Instruments – Ultra Low Power, Rail-to-Rail Output, Fully-Differential Amplifier

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THS4532
SLOS829A – FEBRUARY 2013 – REVISED JULY 2015
9.2.2.1 Design Requirements
To show achievable performance with a high performance audio ADC, the THS5432 is tested as the drive
amplifier for the PCM4204. The PCM4204 is a high-performance, four-channel analog-to-digital converter (ADC)
designed for professional and broadcast audio applications. The PCM4204 architecture uses a 1-bit delta-sigma
modulator per channel incorporating an advanced dither scheme for improved dynamic performance, and
supports PCM output data. The PCM4204 provides flexible serial port interface and many other advanced
features. Refer to the PCM4204 data sheet for more information. Figure 89 shows the circuit.
9.2.2.2 Detailed Design Procedure
The PCM4204 EVM is used to test the audio performance of the THS5432 as a drive amplifier. The standard
PCM4204 EVM is provided with 4x OPA1632 fully-differential amplifiers, which use the same pin out as the
THS5432. For testing, one of these amplifiers is replaced with a THS5432 device in same package (MSOP), gain
changed to 1 V/V, and power supply changed to single supply 5 V. With single supply +5-V supply the output
common-mode of the THS5432 defaults to 2.5 V as required at the input of the PCM4204. So the resistor
connecting the V_OCM input of the THS5432 to the input common-mode drive from the PCM4204 is optional and
no performance change was noted with it connected or removed. The EVM power connections were modified by
connecting positive supply inputs, 15 V, 5 VA, and 5 VD, to a 5-V external power supply (EXT 3.3 was not used)
and connecting –15 V and all ground inputs to ground on the external power supply so only one external 5-V
supply was needed to power all devices on the EVM.
An audio analyzer is used to provide an analog audio input to the EVM and the PCM formatted digital output is
read by the digital input on the analyzer. Data was taken at f_S = 96 kHz, and audio output uses PCM format.
Other data rates and formats are expected to show similar performance in line with that shown in the data sheet.
9.2.2.3 Application Curves
Figure 90 shows the THD+N vs Frequency with no weighting and Figure 91 shows an FFT with 1-kHz input tone.
Input signal to the PCM4204 for these tests is –0.5 dBFS. Table 7 summarizes results of testing using the
THS5432 + PCM4204 versus typical Data Sheet performance, and show it make an excellent drive amplifier for
this ADC.
−95
−97
−99
−101
−103
−105
−107
−109
−111
−113
−115
20
100
1k
10k 20k
Frequency (Hz)
G075
Figure 90. THS5432 + PCM4204 THD+N vs Frequency With
No Weighting
0
−10
−20
−30
−40
−50
−60
−70
−80
−90
−100
−110
−120
−130
−140
−150
20
100
1k
10k
Frequency (Hz)
Figure 91. THS5432 + PCM4204 1-kHz FFT
24k
G076
Table 7. 1-kHz AC Analysis: Test Circuit versus PCM4204 Data Sheet
Typical Specifications (f_S = 96 kSPS)
CONFIGURATION
TONE
THS5432 + PCM4204
1 kHz
PCM4204 Data Sheet (typical)
1 kHz
THD + N
–106 dB
–103 dB
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