1
FEATURES
DESCRIPTION
140
120
100
80
60
40
20
0
20
f Frequency Hz
Amplitude
dB
G018
5k
15k
20k
12k
10k
9k
8k
7k
6k
Closest Open-Loop
Competitor
TIClosed-Loop
Fundamental
AudioInput
40dB
Inprovement
2
nd
Order
Sideband
AudioInput=10kHz
SupplyRipple=1kHz,500mVpp
3
rd
Order
Sideband
f Frequency Hz
20
100
1k
10k
THD+N
T
otalHarmonicDistortion+Noise
%
20k
G019
0.01
10
0.1
1
P =3W
O
SupplyRipple=1kHz,500mVpp
ClosestOpen-Loop
Competitor
TIClosed-Loop
www.ti.com ........................................................................................................................................................................................... SLOS570 – DECEMBER 2008
20-W STEREO DIGITAL AUDIO POWER AMPLIFIER WITH EQ/DRC and FEEDBACK
Audio Input/Output
Benefits
–
20-W Into an 8-
Load From an 18-V Supply
–
EQ: Speaker Equalization Improves Audio
Performance
–
Wide PVCC Range (10 V to 26 V); 3.3 V
Digital Supply
–
DRC: Enables Speaker Protection and
Night-Mode Listening.
–
Supports One Serial Audio Input (8 kHz - 48
kHz Sample Rates) (LJ/RJ/I2S)
–
Autobank Switching: Preloaded
Coefficients for Three Different Sample
–
Power-Stage Feedback Allows Operation
Rates Eliminates the Need to Update
From Poorly Regulated Power Supplies
Coefficients When Sample Rate Changes
Audio/PWM Processing
–
Autodetect: Automatically Detects
–
Factory-Trimmed Internal Oscillator for
Sample-Rate Changes Eliminating the Need
Automatic Rate Detection
for External Microprocessor Intervention
–
High-End 32-Bit Data Path Audio Processor
–
Closed-Loop Power Stage: Enables Wide
–
14 Biquads for Speaker EQ
PVCC Operating Range and Reduced
–
Dynamic Range Control (DRC)
Power Supply Ripple Distortion
The TAS5708 is a 20-W, efficient, digital audio power amplifier for driving stereo bridge-tied speakers. A 32-bit
datapath eliminates the need for pre-scaling before processing and preserves signal integrity without sacrificing
dynamic range. A digital audio processor with fully programmable digital filters allows designers to custom tune
speakers for optimum sound in small enclosures. A programmable DRC can adjust power levels for a scaleable
design while also enabling night-mode listening modes.
The closed-loop architecture allows the device to operate from poorly regulated supplies.
Figure 1 below shows
the benefit of the feedback architecture when a noisy supply (1kHz, 500mVpp ripple) modulates a 10kHz audio
input. The figure shows a 40dB improvement in sideband suppression when compared to an open-loop design.
This correlates directly to a 24dB improvement in distortion as seen in
Figure 2.
Figure 1. Supply Ripple Intermod Distortion
Figure 2. THD+N vs Frequency
1
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas
Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
PRODUCTION DATA information is current as of publication date.
Copyright 2008, Texas Instruments Incorporated
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.