AS3501 AS3502
L o w P o w e r Am b i e n t N o i s e - C a n c e l l i n g Sp e a k e r D r i v e r
Da ta Sh ee t
1 General Description
The AS3501/02 are speaker driver with Ambient Noise
Cancelling function for headsets, headphones or ear
pieces. It is intended to improve quality of e.g. music lis-
tening, a phone conversation etc. by reducing back-
ground ambient noise.
The fully analog implementation allows the lowest power
consumption, lowest system BOM cost and most natural
received voice enhancement otherwise difficult to
achieve with DSP implementations. The device is
designed to be easily applied to existing architectures.
An internal OTP-ROM can be optionally used to store
the microphones gain calibration settings.
The AS3501/02 can be used in different configurations
for best trade-off of noise cancellation, required filtering
functions and mechanical designs.
The simpler feed-forward topology is used to effectively
reduce low frequency background noise. The feed-back
topology with either 1 or 2 filtering stages can be used to
reduce noise for a larger frequency range, and to even
implement transfer functions like speaker equalization,
Baxandall equalization, high/low shelving filter and to set
a predefined loop bandwidth.
The filter loop is optimized by the user for specific head-
set electrical and mechanical designs by dimensioning
simple R, C components.
Most headset implementations will make use of a single
noise detecting microphone. Two microphones could be
used to allow for increased flexibility of their location in
the headset mechanical design. Using the bridged mode
allows to even drive high impedance headsets.
Line Input
volume control via serial interface or volume pin
64 steps @ 0.75dB and MUTE, pop-free gain setting
single ended stereo or mono differential mode
ANC processing
feed-forward cancellation
feed-back cancellation with filter loop transfer func-
tion definable via simple RC components
simple in production SW calibration
12-30dB noise reduction (headset dependent)
10-2000Hz wide frequency active noise attenuation
(headset dependent)
Monitor Function
for assisted hearing, i.e. to monitor announcements
fixed (OTP prog.) ambient sound amplification to
compensate headphone passive attenuation
volume controlled ambient sound amplification
mixed with fixed (OTP prog.) attenuation of LineIn
Incremental Functions
ANC with or without music on the receiving path
improved dynamic range playback
simple and low cost single noise detection micro-
phone implementation
OTP ROM for automatic trimming during production
Performance Parameter
5/3.8mA @ 1.5V stereo/mono ANC; <1uA quiescent
extended PSRR for 217Hz
2 Key Features
Microphone Input
128 gain steps @0.375dB and MUTE with AGC
differential, low noise microphone amplifier
single ended or differential mode
supply for electret microphone
MIC gain OTP programmable
Interfaces
2 wire serial control mode & volume inputs
calibration via Line-In or 2-wire serial interface
single cell or fixed 1.0-1.8V supply with internal CP
Package
AS3501 QFN24 [4x4mm] 0.5mm pitch
AS3502 QFN32 [5.x5mm] 0.5mm pitch
High Efficiency Headphone Amplifier
2x34mW, 0.1% THD @ 16 , 1.5V supply,
100dB SNR
bridged mode for e.g. 300
loads
3 Applications
Ear pieces, Headsets, Hands-Free Kits, Mobile Phones,
Voice Communicating Devices
click and pop less start-up and mode switching
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Revision 1.13
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AS3501 AS3502 1v2
Data Sheet
Figure 1. AS3501 Feed Forward ANC Block Diagram
Figure 2. AS3502 Feed-Back Block Diagram
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Revision 1.13
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AS3501 AS3502 1v2
Data Sheet
Contents
1 General Description
2 Key Features
3 Applications
4 Pinout
............................................................................................................................ 1
.......................................................................................................................................1
........................................................................................................................................ 1
..............................................................................................................................................4
...............................................................................................................................................5
................................................................................................................................................... 4
4.1 Pin Assignment
4.2 Pin Description
5 Absolute Maximum Ratings
6 Electrical Characteristics
8 Detailed Description
8.1 Audio Line Input
8.2 Microphone Input
8.3 Headphone Output
8.4 Operational Amplifier
8.5 SYSTEM
8.6 VNEG Charge Pump
............................................................................................................... 6
..................................................................................................... 9
................................................................................................................... 7
7 Typical Operating Characteristics
.........................................................................................................................13
...........................................................................................................................................13
.........................................................................................................................................14
.......................................................................................................................................16
...................................................................................................................................17
...................................................................................................................................20
...............................................................................................................20
....................................................................................................................23
......................................................................................................................................................18
8.7 OTP Memory & Internal Registers
8.8 2-Wire-Serial Control Interface
9 Register Description
.........................................................................................................................26
.................................................................................................................. 36
.................................................................................................. 40
10 Application Information
12 Ordering Information
11 Package Drawings and Markings
...................................................................................................................... 43
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Revision 1.13
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AS3501 AS3502 1v2
Data Sheet
4 Pinout
4.1
Pin Assignment
Please observe that pin assignment may change in preliminary data sheets.
Figure 3. Pin Assignments (Top View)
CAUTION:
Exposed pad must be connected to VNEG or left unconnected. Exposed pad
must NOT be connected to GND or AGND!
www.austriamicrosystems.com
Revision 1.13
4 - 45
AS3501 AS3502 1v2
Data Sheet
4.2
Pin Description
Please observe that pin description may change in preliminary data sheets.
Table 1. Pin Description for AS3501 AS3502
AS3501 AS3502
24
-
1
2
3
1
2
3
4
5
Pin Name
IOP1L
QLINL
QMICL
AGND
LINL
Type
ANA IN
Description
Filter OpAmp1 Input Left Channel
ANA OUT Line In Gain Stage Output Left Channel
ANA OUT MIC Gain Stage Output Right Channel
ANA IN
ANA IN
DIG IN
ANA IN
DIG IO
MIXED IO
DIG IN
ANA IN
Analog Reference
Line In Left Channel
During Application Trim Mode Write – CSDA
During Application Trim Mode Burn - VNEG
LineIn Right Channel
During Application Trim Mode Write – CSCL
During Application Trim Mode Burn - Clock
Serial Interface Data
ADC Input for volume regulation
Mode Pin (Power Up/Down, Monitor)
Serial Interface Clock
Microphone In Left Channel
4
6
LINR
5
6
7
8
9
10
11
-
12
13
-
-
14
15
-
16
17
18
-
19
20
21
22
-
-
23
25
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
VOL_CSDA
MODE_CSCL
MICL
ILED
MICS
MICR
QMICR
QLINR
IOP1R
QOP1R
IOP2R
QOP2R
VSS
HPL
HPVSS
HPR
HPVDD
VBAT
n.c.
CPP
GND
CPN
VNEG
ANA OUT Current Output for on-indication LED
ANA OUT Microphone Supply
ANA IN
Microphone Input Right Channel
ANA OUT MIC Gain Stage Output Right Channel
ANA OUT Line In Gain Stage Output Right Channel
ANA IN
ANA IN
ANA IN
FilterOpAmp1 Input Right Channel
Filter OpAmp1 Output Right Channel
Filter OpAmp2 Input Right Channel
ANA OUT Filter OpAmp2 Output Right Channel
SUP IN
Core and Periphery Circuit VSS Supply
ANA OUT Headphone Output Left Channel
SUP IN
Headphone VSS Supply
ANA OUT Headphone Output Right Channel
SUP IN
SUP IN
-
ANA OUT VNEG ChargePump Flying Capacitor Positive Terminal
GND
VNEG ChargePump Negative Supply
ANA OUT VNEG ChargePump Flying Capacitor Negative Terminal
SUP IO
VNEG ChargePump Output
Headphone VDD Supply
VNEG ChargePump Positive Supply
QOP2L
IOP2L
ANA OUT Filter OpAmp2 Output Left Channel
ANA IN
Filter OpAmp2 Input Left Channel
QOP1L
ANA OUT Filter OpAmp1 Output Right Channel
Exposed Pad: connect to VNEG or leave it unconnected
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