THS4521 Datasheet, PDF (41/65 Pages) Texas Instruments – VERY LOW POWER, NEGATIVE RAIL INPUT, RAIL-TO-RAIL OUTPUT, FULLY DIFFERENTIAL AMPLIFIER

www.ti.com
9 Application and Implementation
THS4521, THS4522, THS4524
SBOS458H – DECEMBER 2008 – REVISED JUNE 2015
NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
9.1 Application Information
The following circuits show application information for the THS4521, THS4522, and THS4524 family. For
simplicity, power-supply decoupling capacitors are not shown in these diagrams; see Layout Guidelines for
suggested guidelines. For more details on the use and operation of fully differential amplifiers, refer to the
Application Report Fully-Differential Amplifiers (SLOA054), available for download from the TI web site at
www.ti.com.
9.2 Typical Applications
9.2.1 Audio ADC Driver Performance: THS4521 and PCM4204 Combined Performance
To show achievable performance with a high-performance audio ADC, the THS4521 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 THS4521 as a drive amplifier. The standard
PCM4204EVM is provided with four OPA1632 fully-differential amplifiers, which use the same device pinout as
the THS4521. For testing, one of these amplifiers is replaced with a THS4521 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 THS4521 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
THS4521 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, +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 82 shows the THD+N vs Frequency response with no weighting; Figure 83 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 8 summarizes testing results using the THS4521 together with the
PCM4204 versus typical data sheet performance measurements, and show that it make an excellent drive
amplifier for this ADC.
Copyright © 2008–2015, Texas Instruments Incorporated
Submit Documentation Feedback
41
Product Folder Links: THS4521 THS4522 THS4524