Datasheet
0
Frequency (Hz)
-95
97
99
101
103
-
-
-
-
-
-
-
-
-
-
105
107
109
111
113
115
THD+N (dB)
100
1 k 10 k 20 k
THS4521 and PCM4204 THD+N
vs FREQUENCY (No Weighting)
0
Frequency (Hz)
0
10
20
30
40
50
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
60
70
80
90
100
110
120
130
140
150
FFT (dBFS)
100
1 k 10 k 20 k
THS4521 and PCM4204
1-kHz FFT
THS4521
THS4522
THS4524
www.ti.com
SBOS458F –DECEMBER 2008–REVISED SEPTEMBER 2011
Audio ADC Driver Performance: +15 V, +5 VA and +5 VD, to a +5-V external power
THS4521 and PCM4204 Combined supply (EXT +3.3 was not used) and connecting –15
Performance V and all ground inputs to ground on the external
power supply. Note only one external +5-V supply
To show achievable performance with a
was needed to power all devices on the EVM.
high-performance audio ADC, the THS4521 is tested
as the drive amplifier for the PCM4204. The A SYS-2722 Audio Analyzer from Audio Precision
PCM4204 is a high-performance, four-channel ADC (AP) provides an analog audio input to the EVM; the
designed for professional and broadcast audio PCM-formatted digital output is read by the digital
applications. The PCM4204 architecture uses a 1-bit input on the AP.
delta-sigma (ΔΣ) modulator per channel that
Data were taken using a 256-f
S
system clock to
incorporates an advanced dither scheme for
achieve f
S
= 48-kHz measurements, and audio output
improved dynamic performance, and supports PCM
uses PCM format. Other data rates and formats are
output data. The PCM4204 provides a flexible serial
expected to show similar performance in line with that
port interface and many other advanced features.
shown in the product data sheet.
Refer to the PCM4204 product data sheet for more
information.
Figure 76 shows the THD+N vs Frequency response
with no weighting; Figure 77 shows an FFT of the
The PCM4204EVM can test the audio performance of
output with 1-kHz input tone. Input signals to the
the THS4521 as a drive amplifier. The standard
PCM4204 for these tests is 0.5 dBFS. Dynamic range
PCM4204EVM is provided with four OPA1632
is also tested at –60 dBFS, f
IN
= 1 kHz, and
fully-differential amplifiers, which use the same device
A-weighted. Table 4 summarizes testing results using
pinout as the THS4521. For testing, one of these
the THS4521 together with the PCM4204 versus
amplifiers is replaced with a THS4521 device in same
typical data sheet performance measurements, and
package (MSOP), and the power supply changes to a
show that it make an excellent drive amplifier for this
single-supply +5V. Figure 78 shows the modifications
ADC.
made to the circuit. Note the resistor connecting the
V
OCM
input of the THS4521 to the input
The test circuit shown in Figure 78 has a gain = 0.27
common-mode drive from the PCM4204 is shown
and attenuates the input signal. For applications that
removed and is optional; no performance change was
require higher gain, the circuit was modified to gains
noted with it connected or removed. The THS4521 is
of G = 1, G = 2, and G = 5 by replacing the feedback
operated with a +5-V single-supply so the output
resistors (R33 and R34) and re-tested to show
common-mode defaults to +2.5 V as required at the
performance.
input of the PCM4204. The EVM power connections
were modified by connecting positive supply inputs,
Figure 76. THS4521 and PCM4204: THD+N versus
Figure 77. THS4521 and PCM4204 1-kHz FFT
Frequency with No Weighting
Copyright © 2008–2011, Texas Instruments Incorporated Submit Documentation Feedback 31
Product Folder Link(s): THS4521 THS4522 THS4524