THS4521 datasheet(31/48 Pages) TI

31 / 48 page

Frequency (Hz)

101

103

105

107

109

111

113

115

100

1 k

10 k 20 k

THS4521 and PCM4204 THD+N

vs FREQUENCY (No Weighting)

Frequency (Hz)

100

110

120

130

140

150

100

1 k

10 k 20 k

THS4521 and PCM4204

1-kHz FFT

THS4521

THS4522

THS4524

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SBOS458D – DECEMBER 2008 – REVISED AUGUST 2010

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

show

achievable

performance

with

was needed to power all devices on the EVM.

high-performance audio ADC, the THS4521 is tested

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-fS system clock to

incorporates

advanced

dither

scheme

for

achieve fS = 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

provided

with

four

OPA1632

is also tested at –60 dBFS, fIN = 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

VOCM

input

the

THS4521

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

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Product Folder Link(s): THS4521 THS4522 THS4524

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