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SLOS570 – DECEMBER 2008
20-W STEREO DIGITAL AUDIO POWER AMPLIFIER WITH EQ/DRC and FEEDBACK
1
•
FEATURES
Audio Input/Output
– 20-W Into an 8-Ω Load From an 18-V Supply
– Wide PVCC Range (10 V to 26 V); 3.3 V
Digital Supply
– Supports One Serial Audio Input (8 kHz - 48
kHz Sample Rates) (LJ/RJ/I
2
S)
– Power-Stage Feedback Allows Operation
From Poorly Regulated Power Supplies
Audio/PWM Processing
– Factory-Trimmed Internal Oscillator for
Automatic Rate Detection
– High-End 32-Bit Data Path Audio Processor
– 14 Biquads for Speaker EQ
– Dynamic Range Control (DRC)
•
•
Benefits
– EQ: Speaker Equalization Improves Audio
Performance
– DRC: Enables Speaker Protection and
Night-Mode Listening.
– Autobank Switching: Preloaded
Coefficients for Three Different Sample
Rates Eliminates the Need to Update
Coefficients When Sample Rate Changes
– Autodetect: Automatically Detects
Sample-Rate Changes Eliminating the Need
for External Microprocessor Intervention
– Closed-Loop Power Stage: Enables Wide
PVCC Operating Range and Reduced
Power Supply Ripple Distortion
DESCRIPTION
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.
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
20
0
−20
Closest Open-Loop
Competitor
TI Closed-Loop
nd
10
THD+N − Total Harmonic Distortion + Noise − %
Fundamental
Audio Input
Closest Open-Loop
Competitor
TI Closed-Loop
2 Order
Sideband
Amplitude − dB
−40
40 dB
Inprovement
1
−60
−80
−100
−120
3 Order
Sideband
rd
0.1
Audio Input = 10 kHz
Supply Ripple = 1 kHz, 500 mVpp
P
O
= 3 W
Supply Ripple = 1 kHz, 500 mVpp
−140
5k
6k
7k
8k 9k 10k
12k
15k
20k
G018
0.01
20
100
1k
f − Frequency − Hz
G019
10k 20k
f − Frequency − Hz
Figure 1. Supply Ripple Intermod Distortion
1
Figure 2. THD+N vs Frequency
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.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2008, Texas Instruments Incorporated
TI [ TEXAS INSTRUMENTS ]
