2004 California Micro Devices Corp. All rights reserved.
01/09/04
430 McCarthy Blvd., Milpitas, California 95035
L
Tel: (408) 263-3214
L
Fax: (408) 263-7846
L
www.calmicro.com
1
CMAMP110
Microphone Amplifier
Features
Microsoft PC99 & PC2001 compliant
Differential and Single-ended Microphone Inputs
Internally frequency compensated for unity gain
20dB DC voltage gain (maximum)
Buffered DC bias voltage for external microphone
Very low supply current (< 3.0 mA)
20K
minimum input impedance
Low Total Harmonic Distortion (0.03% at
1 KHz typical)
Small MSOP package
Lead-free version available
Applications
Computers
Mobile Phones
PDA's
MP3 Players
Digital Cameras
Video Tape Recorders
Product Description
The CMAMP110 Microphone Amplifier selects (via
MIC_SELECT) between and amplifies Internal and
External Microphone input signals. The device is
designed to be compliant with Microsoft PC99 and
PC2001 specifications. The CMAMP110 contains the
equivalent of 7 operational amplifiers and 19 precision
resistors, and is intended for use in PC audio applica-
tions. The Internal Microphone input is differential, but
it can also be used single-ended by simply grounding
one of the inputs through a capacitor. The External
Microphone input is single-ended. A logic high level on
the MIC_SELECT pin selects the external microphone
input. Since the chip supplies the DC bias for the exter-
nal microphone (EXT_MIC_BIAS), both dynamic and
electret type microphones may be used. The output
amplifier is unity gain stable and is capable of driving a
resistive load in excess of 10K
.
The CMAMP110 Microphone Amplifier is housed in a
space saving MSOP-8 package and is optionally avail-
able with lead-free finishing.
Electrical Schematic
VREF
MIC_SELECT
INT_MIC
-
INT_MIC
+
EXT_MIC_IN
V
-
V
OUT
V
+
EXT_MIC_BIAS
SW1
SW2
500K
500
K
500K
500K
50
0K
50
0K
3
2
7
8
6
5
1
4
2.5K
R
BIAS
2004 California Micro Devices Corp. All rights reserved.
2
430 McCarthy Blvd., Milpitas, California 95035
L
Tel: (408) 263-3214
L
Fax: (408) 263-7846
L
www.calmicro.com
01/09/04
CMAMP110
Ordering Information
Note 1: Parts are shipped in Tape & Reel form unless otherwise specified.
PIN DESCRIPTIONS
PIN
NAME
DESCRIPTION
1
MIC_SELECT
Microphone Select logic input control. The external microphone input is selected when
the MIC_SELECT signal (pin 1) is at Logic "1" (> 3.5 volts), and the internal microphone
inputs are selected by applying Logic "0" to the pin (< 1.5V).
2
V
OUT
Amplifier output pin.
3
EXT_MIC_BIAS
External microphone bias output.
4
V+
Positive supply pin.
5
INT_MIC
-
Inverting internal microphone differential input. Can be operated as a single-ended input
by connecting a 0.22
F (or greater) capacitor between pin 6 and V
-
.
6
INT_MIC+
Non-inverting internal microphone differential input. Can be operated as a single-ended
input by connecting a 0.22
F (or greater) capacitor between pin 5 and V
-
.
7
V
-
Negative supply pin.
8
EXT_MIC_IN
External microphone signal input.
PACKAGE / PINOUT DIAGRAM
Note: This drawing is not to scale.
8-pin MSOP
1
2
3
4
8
7
6
5
MIC_SELECT
V
OUT
EXT_MIC_BIAS
V
+
EXT_MIC_IN
V
-
INT_MIC
+
INT_MIC
-
Top View
PART NUMBERING INFORMATION
Pins
Package
Standard Finish
Lead-free Finish
Ordering Part
Number
1
Part Marking
Ordering Part
Number
1
Part Marking
8
MSOP-8
CMAMP110M A110
CMAMP110MR R110
2004 California Micro Devices Corp. All rights reserved.
01/09/04
430 McCarthy Blvd., Milpitas, California 95035
L
Tel: (408) 263-3214
L
Fax: (408) 263-7846
L
www.calmicro.com
3
CMAMP110
Specifications
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. For guaranteed specifications
and the test conditions, see the Electrical Operating Characteristics.
Note 2: Human Body Model, 1.5K
in series with 100pF (MIL-STD-883, Method 3015).
Note 3: Continuous short circuit operation at elevated ambient temperatures can result in exceeding the maximum allowed junction
temperature of 150C.
Note 1: Operating conditions indicate ratings for which the device is intended to be functional, but specific performance is not guar-
anteed. For guaranteed specifications and the test conditions, see the Electrical Operating Characteristics.
ABSOLUTE MAXIMUM RATINGS
(SEE NOTE 1)
PARAMETER
RATING
UNITS
ESD Protection (HBM, Note 2)
+2000
V
Differential Input Voltage
+/
-
Supply Voltage
V
Voltage at any Input/Output Pin
[(V
-)
- 0.3] to [(V+) + 0.3]
V
Storage Temperature Range
-40 to +150
C
Junction Operating Temperature
+125
C
Lead Soldering Temperature (10 seconds)
+260
C
Supply Voltage
[
(V+) - (V
-)
]
7.5
V
Current at Input Pin
5
mA
Current at Output Pin (Note 3)
15
mA
Current at Power Supply Pin
15
mA
STANDARD OPERATING CONDITIONS
(SEE NOTE 1)
PARAMETER
RATING
UNITS
Maximum Power Dissipation
200
mW
Ambient Operating Temperature Range
0 to +70
C
Supply Voltage
3.3 to 5.5
V
2004 California Micro Devices Corp. All rights reserved.
4
430 McCarthy Blvd., Milpitas, California 95035
L
Tel: (408) 263-3214
L
Fax: (408) 263-7846
L
www.calmicro.com
01/09/04
CMAMP110
Specifications (cont'd)
Note 1: All tests at 25C, V+ = +5V, V- = 0V unless otherwise noted.
ELECTRICAL OPERATING CHARACTERISTICS
(SEE NOTE 1)
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
R
IN
Input Impedance
All Inputs
20
40
K
A
V
AC Voltage Gain
V
IN
= 100 mV rms,
R
L
=10K
18
20
dB
V
MIC_IN
Microphone Input Signal Level
110
mV rms
V
OUT
Output Signal Level
R
L
=10K
1
V rms
V
EXT_MIC_BIAS
External Microphone Bias Voltage
No Load
I
SOURCE
= 0.8mA
2.0
4.6
2.6
V
V
R
BIAS
Microphone Bias Resistor
2.0
2.5
K
GBW
Gain Bandwidth Product
R
L
=10K
2.0
MHz
SR
Slew Rate
R
L
=10K
1.3
V/
s
T.H.D.
Total Harmonic Distortion
f = 1KHz, V
IN
= 100mV rms,
R
L
=10K
0.03
%
V
IH
MIC_SELECT Logic High Voltage
3.5
V
V
IL
MIC_SELECT Logic Low Voltage
1.5
V
t
SW
Microphone Switching Time
2
s
I
SUP
Supply Current
1.5
3.0
mA
I
SC
Output Short Circuit Current
V
OUT
= 0V
15
mA
R
L
Load Impedance Applied to V
OUT
10
K
2004 California Micro Devices Corp. All rights reserved.
01/09/04
430 McCarthy Blvd., Milpitas, California 95035
L
Tel: (408) 263-3214
L
Fax: (408) 263-7846
L
www.calmicro.com
5
CMAMP110
Application Information
CMAMP110 Design Considerations
1. General Overview
The CMAMP110 is very straightforward to apply, but a
few precautions are worth noting. It is recommended
that the power supply pin, V+ (pin 4), be bypassed with
a parallel combination of a 4.7
F and a 0.1
F capacitor
to minimize noise and hum pickup. In addition, a 100
resistor may be inserted in series to form a RC filter
between the the power supply feed and the V+ pin to
the CMAMP110.
Also, in that regard, lead dress for the
microphone inputs on the PCB should either be
shielded from or spaced from noise sources. The V
-
input on the device (pin 7) should be connected to the
"clean analog ground".
2. Passive Component Selection
Selection of the microphone input coupling capacitors
can be made using the following equation:
Where:
R
IN
= Microphone Input Impedance (40K
typical)
MIN
= Minimum Input Frequency
For example, for
MIN
= 20Hz,
C
should be selected
for 0.22
F (or greater). The above equation may also
be used to select the output coupling capacitor.
3. Microphone Bias
The CMAMP110 provides a nominal 4.6 volt stable ref-
erence and 2.5K
resistor to bias the microphone. For
a bias current of 800
A, a 2.6 volt bias voltage results.
However, if other voltages are desired, a resistor can
be inserted in series with the microphone bias output
(pin 3) whose value, R
EXT
, can be chosen using the
following equation:
Where:
V
BMIC
= 4.6 volts
R
BIAS
= 2.5 K
V
B
= Desired Microphone Bias Voltage
I
B
= Microphone Bias Current
For example, an electret condenser microphone that
operates on 1.5V and 0.5mA, R
EXT
should be selected
to be 3.9K
(nearest standard value).
4. Microphone Select
The CMAMP110 has provisions for the selection of
either the internal microphone and external micro-
phone inputs. The external microphone is selected
when the MIC_SELECT signal (pin 1) is at Logic "1" (>
3.5 volts), and the internal microphone is selected by
applying Logic "0" to the pin (< 1.5V). The switching
time is approximately 2 ms. For static applications
where only one input is used, pin 1 can simply be
strapped to either V
-
or V+.
5. Internal Microphone
The CMAMP110 provides for a differential (floating)
input for the Internal microphone where INT_MIC+ (pin
6) is the "non-inverting" input and INT_MIC
-
(pin 5) is
the "inverting" input. The CMAMP110 may be operated
single-ended by connecting a 0.22
F (or greater)
capacitor between either pin 5 or pin 6 and V
-
.
6. Start Up
Application of the CMAMP110 requires AC coupling
the inputs and outputs (see Passive Component Selec-
tion). Both the Internal Microphone inputs (INT_MIC+
and INT_MIC
-
) and the External Microphone input
(EXT_MIC_IN) are DC biased at half the supply volt-
age with an equivalent impedance of about 500K
. As
a result, a start up transient will occur as the capacitors
charge to half of the rail. The time for the amplifier
inputs and outputs to settle is given by:
C
1
2
R
IN
f
MIN
-----------------------------------
=
R
EXT
V
BMIC
I
B
R
BIAS
(
)
V
B
I
B
--------------------------------------------------------------
=
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