P
A
ASP
TruBass Audio Enhancement Processor
AP8111
PRELIMINARY
1 Overview
The
AP8111
is a bass enhancement processor based on SRS Labs, Inc.’s patented TruBass technology. TruBass is a
revolutionary psychoacoustic bass enhancement technology that provides deep, rich bass to small speakers without the need
for a subwoofer or additional extra physical components. Deep bass now becomes possible even through speakers with
limitations in driver and cabinet design. TruBass circuitry actively monitors the low-frequency content of an audio signal
and optimizes the frequency and amplitude spectrum of the output signal to enhance bass perception. For systems with a
subwoofer, TruBass complements and enhances bass performance.
TruBass is therefore most suitable for applications that use small size speakers yet need to deliver the best audio quality or
home theatre effect: Mini or Micro Stereo Sound Systems, TV, CD, Boombox, Car Audio, DVD Receiver, Set-Top-Box, and
other compact hi-fi systems such as Discman, MD, MP3 player, as well as PCs.
2 Features
Operating Voltage 4.75V to 5.25V
Low Operation Current 10mA typ
Power down and Bypass mode selection
Analog switch for mode and gain control
External adjustment for speaker size setting (small, medium and large)
Bipolar Technology
Chip Package
28 pins SOP
The TruBass technology rights in the
AP8111
are owned by SRS Labs, a United States. Corporation and licensed to ASP
Microelectronics Ltd. TruBass is protected under US and foreign patents issues and/or pending. TruBass and the
symbol
are trademarks of SRS Labs, Inc. in the United State and selected foreign countries. Neither the purchase of the
AP8111,
nor the
corresponding sale of audio enhancement equipment conveys the right to sell commercialized recordings made with any SRS
technology. SRS Labs requires all set makers to comply with all rules and regulations as outlined in the SRS Trademark Usage
Manual separately provided.
For further information, please contact:
SRS Labs, Inc.
2909 Daimler Street, Santa Ana, CA 92705 USA
Tel: 949-442-1070
Fax: 949-852-1099
http://www.srslabs.com
ASP Microelectronics Ltd.
Unit 218, 2/F., Tech Centre,
72 Tat Chee Ave., Kowloon Tong, Hong Kong
Tel:(852) 2797 3288
Fax: (852) 2797 3112
http://www.asp.com.hk
Revision 2.4
1
[CAUTION]
The information in this publication is believed
to be accurate in all respects at the time of
publication but is subject to change without
notice. ASP Microelectronics Ltd. assumes no
responsibility for errors and omissions, and
disclaims responsibility for any consequences
resulting from the use of information included
herein. Additionally, ASP Microelectronics Ltd.
assumes no responsibility for the functioning of
undocumented features or parameters.
15 April., 2002
P
A
ASP
Pin #
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
Pin Name
LOUT
LIN
VREF
NC
CB1A
CB1B
CB1
GND
TBGAIN
CB2B
CB2A
CB2
BYPASS
COMPI
CL1
FOUT
COMPC2
NC
VCC
COMPC1
CB3B
CB3A
CB3
CL2B
NC
CL2A
RIN
ROUT
- analog output pin
- analog input pin
- analog bi-directional pin
- digital input pin
- power pin
Type
AOUT
AIN
AOUT
-
AI/O
AI/O
AI/O
PWR
DIN
AI/O
AI/O
AI/O
DIN
AIN
AI/O
AOUT
AI/O
-
PWR
AI/O
AI/O
AI/O
AI/O
AI/O
-
AI/O
AIN
AOUT
Descriptions
Left channel audio line output
Left channel audio line input
2.25V analog reference
Not used
100Hz band-pass filter circuit
100Hz band-pass filter circuit
100Hz band-pass filter circuit
Analog ground
TruBass gain control. +6dB gain when this pin short to ground.
40/150Hz band-pass filter circuit
40/150Hz band-pass filter circuit
40/150Hz band-pass filter circuit
Power down/ Bypass / TruBass-enable selection
Compressor input
Low-pass filter capacitor
Filter output
Compressor capacitor
Not used.
5 volts power supply
Compressor output
60/200Hz band-pass filter circuit
60/200Hz band-pass filter circuit
60/200Hz band-pass filter circuit
Low-pass filter capacitor
Not used
Low-pass filter capacitor
Right channel audio line input
Right channel audio line output
AP8111
3 Device Pin Out and Pin Descriptions
AOUT
AIN
AI/O
DIN
PWR
Revision 2.4
2
15 April., 2002
P
A
ASP
AP8111
4 Pin Configuration
1
2
3
4
5
6
7
8
9
10
11
12
13
14
LOUT
LIN
VREF
NC
CB1A
CB1B
ROUT
RIN
CL2A
NC
CL2B
CB3
28
27
26
25
24
23
22
21
20
19
18
17
16
15
1
CB1
GND
CB3A
CB3B
TBGAIN COM PC1
CB2B
CB2A
CB2
BYPASS
COM PI
VCC
NC
COM PC2
FOUT
CL1
5 Operating Modes
The chip can be configured in 3 modes of operations – Power down mode, bypass mode, TruBass mode.
In power down mode, the chip is power down and consumed minimal current.
In bypass mode, line in audio signal is pass directly to the output.
In TruBass mode, line in audio signal is enhanced with the TruBass algorithm.
The
Bypass
pin (pin 11) is used to select the operating mode. When the pin is forced to 0v, the chip is powered down and when
the pin is at float (or Vcc/2) and at 5v, the mode is set to Bypass and TruBass Enabled respectively.
An additional +6dB gain is enabled by pulling the pin TBGAIN to ground.
6 Speaker Size and Filter Center Frequencies selection
The configuration of the TruBass band-pass filters depends on the speaker size for the system. There are three configurations:
small, medium and large. Each configuration uses three bandpass filters, but with different center frequencies for the filters as
follows:
Speaker Size
Small
Medium
Large
Filter Center Frequencies
100Hz
60Hz
40Hz
The low pass filter cutoff frequency and the band pass filter center frequencies can be adjusted to match the frequency response of
the speakers being used. Generally, the speaker size setting should be selected so that the lowest of the band pass center
frequencies is just above the low cutoff frequency of the speaker system.
All configurations require the 100Hz filter, so its center frequency is fixed. The center frequencies of the other two filters are
configured by the external resistors placed on pins CB2, CB2A, CB2B, CB3, CB3A, CB3B.
Revision 2.4
3
15 April., 2002
P
A
ASP
AP8111
ROUT
LOUT
RIN
C4
4.7U
LIN
C1
4.7U
7 Application circuit
C2
4.7U
C3
4.7U
1
2
10U
C5
3
4
R1
C7
0.1U
31.6K
C6
0.1U
R2
4.53K
R3
5
6
7
8
JP2
1
2
J1
1-2 +6dB
open 0dB
R7
56.2K
R5
21K
VCC
158K
R4
jumper set for gain control
8
6
4
2
C8
0.1U
J3
57.6K
7
5
3
1
0.1U
C9
9
10
11
12
13
R8
13K
14
AP8111
LOUT
LIN
VREF
NC
CB1A
CB1B
CB1
GND
TBGAIN
CB2B
CB2A
CB2
BYPASS
COMPI
U1
ROUT
RIN
CL2A
NC
CL2B
CB3
CB3A
CB3B
COMPC1
VCC
NC
COMPC2
FOUT
CL1
28
27
26
25
24
23
22
R16
21
20
19
18
17
16
15
33K
R10
10U
C15
10U
C16
8.87K
2.32K
R19
C18
0.1U
R21
37.4K
R20
22.1K
R18
7
5
3
1
33K
0.01U
C17
R15
107K
45.3K
8
6
4
2
0.1U
C19
J4
63.4K
R17
R9
Speaker Setting
Small
J3
J4
1-2, 5-6
1-2, 5-6
1-2, 5-6
3-4, 7-8
3-4, 7-8
3-4, 7-8
R6
3.09K
Medium J3
J4
Large J3
J4
JP3
jumper set for operating mode
1-2
open
2-3
TruBass
Bypass
Power Down
10K
R12
300K
R22
C10
4.7U
10U
C14
R13
4.7U
C11
10K
100K
R11
R14
37.5K
C13
3300P
J2
0.01U
C12
1
2
3
PUNCH CONTROL
10K variable resistor
Tolerance all resistors are ±1%, capacitors are ±10%
Revision 2.4
4
15 April., 2002
P
A
ASP
AP8111
8 Recommended Operating Condition
The following is the recommended operating conditions for the TruBass analog processor
Symbol
VCC
Vi
Vo
Tamb
Parameter
DC supply voltage
DC input voltage range
DC output voltage range
Operating ambient temperature range
Min
4.75
-0.3
0
0
Max
5.25
VCC+0.3
VCC
70
Unit
Volts
Volts
Volts
°C
9 DC Electrical Specifications
Symbol
Vcc
Icc
Ipd
Rin
Vref
Rload
Cload
Vil
Vmid
Vih
Ileak
Parameter
Chip supply voltage
Operating current
Power down supply current
Left/Right input impedance
Analog reference voltage
Resistance load at Left/Right output
Capacitance load at Left/Right
output
Digital input logic low
Mid-level for Tri-level logic
Digital input logic high
Digital input leakage ( except
TBGAIN )
Conditions
Vcc = 5.0
Vcc = 5.0
10
2.02
10
Min
4.75
Typ
5
10
25
2.25
Max
5.25
50
2.48
50
If floated, internal
reference will ensure
Vmid
Vcc = 5.0
Vcc/2 –
10%
Vcc – 0.3
-10
Vcc/2
0.3
Vcc/2 +
10%
10
Units
V
mA
uA
kΩ
V
kΩ
pF
V
V
V
uA
10 AC Electrical Specifications
Symbol
Freq
Vrli
Vrlo
Gerror
SNR
THD
Xtalk
Comp
Rate
Parameter
Audio signal operating frequency
Audio input signal level (0dB level
reference)
Audio output level
Output gain error
Conditions
Inputs AC coupled
-0.5
80
1
-70
2:1
10:1
Min
20
Typ
Max
20000
1
1
0.5
Units
Hz
Vrms
Vrms
dB
dB
%
dB
Rload = 10kΩ
Bypass mode, input
signal @ 0dB 1kHz
Signal to noise ratio
Bypass mode /A-
weighted, input signal @
-60dB 1kHz
Total harmonic distortion
Bypass mode
Input @ 0dB 1kHz
Channel Crosstalk
Bypass mode
TruBass Compressor Ratio
Punch at maximum gain
Attack to decay time constant ratio Absolute value set by
external capacitor
Revision 2.4
5
15 April., 2002
Microcontroller MCU
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