THS4521 datasheet(33/48 Pages) TI

33 / 48 page

Frequency (Hz)

101

103

105

107

109

111

113

115

100

1 k

10 k 20 k

G = 5

G = 1

G = 2

THS4521 and PCM4204 THD+N

vs FREQUENCY (No Weighting, at Higher Gains)

Frequency (Hz)

100

1 k

10 k 20 k

THS4521 and PCM3168 THD+N vs FREQUENCY

(No Weighting)

THS4521

THS4522

THS4524

www.ti.com

SBOS458D – DECEMBER 2008 – REVISED AUGUST 2010

Figure 79 shows the THS4521 and PCM4204 THD+N

EVM is configured for both differential inputs as

versus frequency with no weighting at higher gains.

shown in Figure 60 and for single-ended input as

shown in Figure 61 with 1-k

Ω resistors for RF and RG,

and 24.9-

Ω resistors in series with each output to

isolate the outputs from the reactive load of the

coaxial cables. To limit the noise from the external

EVM and cables, a 2.7-nF capacitor is placed

differentially across the PCM3168A inputs. The

THS4521 is operated with a single-supply +5-V

supply so the output common-mode of the THS4521

defaults to +2.5 V as required at the input of the

PCM3168A. The PCM3168A EVM is configured and

operated as described in the PCM3168AEVM User

Guide. The ADC was tested with an external

THS4521 EVM with both single-ended input and

differential inputs. In both configurations, the results

are the same. Figure 80 shows the THD+N versus

frequency and Table 5 compares the result to the

PCM3168 data sheet typical specification at 1 kHz.

Both graphs show that it makes an excellent drive

amplifier for this ADC. Note: a 2700 series Audio

Figure 79. THS4521 and PCM4204: THD+N versus

Analyzer from Audio Precision is used to generate

Frequency with No Weighting at Higher Gains

the input signals to the THS4521 and to analyze the

digital data from the PCM3168.

Audio ADC Driver Performance:

THS4521 and PCM3168 Combined

Performance

The THS4521 is also tested as the drive amplifier for

the PCM3168A ADC input. The PCM3168A is a

high-performance,

single-chip,

24-bit,

6-in/8-out,

audio coder/decoder (codec) with single-ended and

differential selectable analog inputs and differential

outputs. The six-channel, 24-bit ADC employs a

ΔΣ

modulator and supports 8-kHz to 96-kHz sampling

rates and a 16-bit/24-bit width digital audio output

word on the audio interface. The eight-channel, 24-bit

digital-to-analog converter (DAC) employs a

ΔΣ

modulator and supports 8-kHz to 192-kHz sampling

rates and a 16-bit/24-bit width digital audio input word

on the audio interface. Each audio interface supports

I2S™,

left-/right-justified,

and

DSP

formats

with

16-bit/24-bit word width. In addition, the PCM3168A

Figure 80. THS4521 and PCM3168: THD+N versus

supports the time-division-multiplexed (TDM) format..

Frequency with No Weighting

The PCM3168A provides flexible serial port interface

and many other advanced features. Refer to the

PCM3168A product data sheet for more information.

Table 5. 1-kHz AC Analysis: Test Circuit vs

PCM3168 Data Sheet Typical Specifications

The PCM3168A EVM is used to test the audio

(fS = 48 kSPS)

performance of the THS4521 as a drive amplifier.

The standard PCM3168A EVM is provided with

Configuration

Tone

THD+N

OPA2134

amps

that

are

used

convert

THS4521 and

1 kHz

–92.6 dBc

single-ended inputs to differential to drive the ADC.

PCM3168

For testing, the op amp output series resistors are

PCM3168 Data

1 kHz

–93 dBc

removed from one of the channels and a THS4521,

sheet (typ)

mounted on its standard EVM, is connected to the

ADC inputs via short coaxial cables. The THS4521

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