THS4531A_15 Datasheet, PDF (37/59 Pages) Texas Instruments – THS4531A Ultra Low-Power, Rail-to-Rail Output, Fully Differential Amplifier

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THS4531A
SLOS823B – DECEMBER 2012 – REVISED JUNE 2015
9.2.2.1 Detailed Design Procedure
The PCM4204 EVM is used to test the audio performance of the THS4531A as a drive amplifier. The standard
PCM4204 EVM is provided with 4x OPA1632 fully differential amplifiers, which use the same pin out as the
THS4531A. For testing, one of these amplifiers is replaced with a THS4531A 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 THS4531A defaults to 2.5 V as required at the input of the PCM4204. So the
resistor connecting the V_OCM input of the THS4531A 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.
9.2.2.2 Application Curves
Figure 88 shows the THD+N vs Frequency with no weighting and Figure 89 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
THS4531A + 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 88. THS4531A + 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 89. THS4531A + 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
THS4531A + PCM4204
1 kHz
PCM4204 Data Sheet (typical)
1 kHz
THD + N
–106 dB
–103 dB
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