THS4524-EP Datasheet, PDF (33/48 Pages) Texas Instruments – VERY LOW POWER, NEGATIVE RAIL INPUT, RAIL-TO-RAIL OUTPUT, FULLY DIFFERENTIAL AMPLIFIER

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Audio ADC Driver Performance:
THS4524 and PCM4204 Combined
Performance
To show achievable performance with a high-
performance audio ADC, the THS4524 is tested as
the drive amplifier for the PCM4204. The PCM4204 is
a high-performance, four-channel ADC designed for
professional and broadcast audio applications. The
PCM4204 architecture uses a 1-bit delta-sigma (ΔΣ)
modulator per channel that incorporates an advanced
dither scheme for improved dynamic performance,
and supports PCM output data. The PCM4204
provides a flexible serial port interface and many
other advanced features. Refer to the PCM4204
product data sheet for more information.
The PCM4204EVM can test the audio performance of
the THS4524 as a drive amplifier. The standard
PCM4204EVM is provided with four OPA1632 fully-
differential amplifiers, which use the same device
pinout as the THS4524. For testing, one of these
amplifiers is replaced with a THS4524 device in same
package (MSOP), and the power supply changes to a
single-supply +5V. Figure 79 shows the modifications
made to the circuit. Note the resistor connecting the
V_OCM input of the THS4524 to the input common-
mode drive from the PCM4204 is shown removed
and is optional; no performance change was noted
with it connected or removed. The THS4524 is
operated with a +5-V single-supply so the output
common-mode defaults to +2.5 V as required at the
input of the PCM4204. The EVM power connections
were modified by connecting positive supply inputs,
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0
THS4524 and PCM4204 THD+N
vs FREQUENCY (No Weighting)
100
1k
Frequency (Hz)
10 k 20 k
Figure 77. THS4524 and PCM4204: THD+N versus
Frequency with No Weighting
THS4524-EP
SBOS609A – JUNE 2012 – REVISED AUGUST 2013
+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. Note only one external +5-V supply
was needed to power all devices on the EVM.
A SYS-2722 Audio Analyzer from Audio Precision
(AP) provides an analog audio input to the EVM; the
PCM-formatted digital output is read by the digital
input on the AP.
Data were taken using a 256-f_S system clock to
achieve f_S = 48-kHz measurements, and audio output
uses PCM format. Other data rates and formats are
expected to show similar performance in line with that
shown in the product data sheet.
Figure 77 shows the THD+N vs Frequency response
with no weighting; Figure 78 shows an FFT of the
output with 1-kHz input tone. Input signals to the
PCM4204 for these tests is 0.5 dBFS. Dynamic range
is also tested at –60 dBFS, f_IN = 1 kHz, and A-
weighted. Table 4 summarizes testing results using
the THS4524 together with the PCM4204 versus
typical data sheet performance measurements, and
show that it make an excellent drive amplifier for this
ADC.
The test circuit shown in Figure 79 has a gain = 0.27
and attenuates the input signal. For applications that
require higher gain, the circuit was modified to gains
of G = 1, G = 2, and G = 5 by replacing the feedback
resistors (R33 and R34) and re-tested to show
performance.
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THS4524 and PCM4204
1-kHz FFT
100
1k
Frequency (Hz)
10 k 20 k
Figure 78. THS4524 and PCM4204 1-kHz FFT
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