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Microphone Mixer Evaluation Module
DATA MANUAL: SLOU009
Date: July 1997
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Contents
1. Layout Definition ...................................................................................................... 6 2. Operation .................................................................................................................. 8 3. Input/Output Connections........................................................................................ 9 4. Layout...................................................................................................................... 11 5. Bill of Materials ....................................................................................................... 13
Figures
Figure 1. Mic Mixer EVM Component Placement .............................................................. 6 Figure 2. Mic Mixer EVM Schematic.................................................................................. 9
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1. Layout Definition
The Mic/Mixer EVM is designed to provide basic volume control and a microphone interface to the P-n-P Audio Power Amplifier Evaluation Platform. With the Mic/Mixer plugged in to the P-n-P, the user can sing along with music from a favorite CD (karaoke) or simply use the volume control to adjust the listening level of the line inputs.
Figure 1. Mic Mixer EVM Component Placement
R22 R15 R7 C7 JP1 J2 R24 J1 R_IN J3 L_IN S1 R11 R4 R3 C1 R25 R5 R18 C4 C2 C5 R8 C6 R9 R13 U1
TLC2274
C8 R23
R12 R10 C12
R19
R17 U2 R6
TLC2274
R16 R14
Mic Volume C3
J6 Vdd R_OUT L_OUT
C10 SLOP107 MIC/MIXER Rev. B 1997
C9 R1 R2
R20
Operating the Mic Mixer Evaluation Module (SLOP107)
R21 C11
R Volume L Volume
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TLC2274
U1,2 - TLC2274CD Quad op Amp, RRO, 2MHz C1,5,9 - Capacitor, 1.0 F Ceramic C2,4,6,11 - Capacitor, 47 pF Ceramic C3 - Capacitor, 10 F Electrolytic C7,8 - Capacitor, 2.2 F Ceramic C10,12 - Capacitor, 0.1 F Ceramic R1,2,11 - Pot, 50 k, Slide, Audio Taper R3,5,8,12,14 - Resistor, 10 k Carbon R16,17,18,19 - Resistor, 10 k Carbon R20,21,25 - Resistor, 10 k Carbon R4,6,13,15 - Resistor, 20 k Carbon R22,23,24 - Resistor, 20 k Carbon R9 - Resistor, 47 k Carbon R7 - Resistor, 2.2 k Carbon R10 - Pot, 200 k, 3/4 turn JP1,2 -0.1" header, 2-pin, 3-pin J2 - 1/8" Stereo Jack
Operating the Mic Mixer Evaluation Module (SLOP107)
7
2. Operation
The basis of the Mic/mixer design is the TLC2274 quad CMOS Rail to Rail op amp from TI. The bandwidth, distortion and noise performance of the TLC2274 make it an ideal workhorse in PC audio applications. Power: 5.0 to 16 Vdc, 10 mA Audio Inputs: L/R IN, AC Coupled, 1 Vrms Nominal, G = 0 to 2, individual L/R slide control with audio taper, Audio Outputs: L/R Out, DC Coupled (Vcc/2 offset), THD < 0.004% Nominal 1 kHz.
NOTE:MIC INTERFACE:MIC IN, 1/8" STANDARD INPUT JACK COMPATIBLE WITH MOST ELECTRET OR DYNAMIC MICROPHONES, G = 0 TO 7.5 WITH R19 SET TO MIN, G = 0 TO 83 WITH R19 SET TO MAX. INDIVIDUAL MIC LEVEL SLIDE CONTROL MIXES MIC INPUT TO BOTH LINE OUTPUTS. MIC BIAS OUTPUT SET TO VCC*0.66 SELECTABLE TO RING OR TIP.
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SLOU009
3. Input/Output Connections
Figure 2. Mic Mixer Schematic
T PA
Mic/Mixer EVM, SLOP107 Rev. B
VDD GND
C1 1.0 uF R4 20 k R3 10 k R1 50 k AT mid JP1 mid
2 3
PUMP UP THE VOLUME
J C3 6 10 uF
C4 47 pF R17 10 k R16 10 k
13
R In
J1
U2a
1
R18 10 k U2d
14
R7 2.2 k mic bias R9 47 k C6 47 pF
V DD U1a
1 3 2
12
J4
R Out
R12 10 k R13 20 k R10 200 k LT mid
mid VDD U1d
14 12 13
J2
Ring Tip
C7 2.2 uF
Mic In
R8 C5 1.0 uF 10 k
6 5
U1b
7
R15 20 k R25 10 k R14 10 k
R22 20 k R23 20 k
C2 47 pF
9 10
C8 2.2 uF C11 47 pF R19 10 k R20 10 k
9
JP2 R24 20 k C9 1.0 uF
mid
R11 50 k AT R6 20 k mid mid
U1c
8
L In
J3 R2 50 k AT mid
R5 10 k
6 5
U2b
7
R21 10 k U2c
8
03/04/97
* use 0.1 bypass on U1 (C12), U2 (C10) > red traces must be as short as possible!
mid
10
J5
L Out
mid
Each audio input channel is AC coupled through a 1 uF capacitor into a volume control potentiometer. The slide pot is logarithmic (audio Taper) which compensates for the nonlinear response of the ear resulting in a linear volume control. A single stage amp with a gain of -2 is used to buffer the volume control form the summing stage amplifier. A midrail (virtual ground) voltage is generated with a voltage divider from the supply voltage and buffered with a single amplifier. This voltage is used to bias the AC signal to the center of the operating voltage range to prevent positive or negative clipping of the audio signals. The voltage is set to Vcc/2. The microphone interface is compatible with common SoundBlaster type electret mics and dynamic mics. Electret mics require a bias voltage to operate. The bias circuit can be
Operating the Mic Mixer Evaluation Module (SLOP107)
9
configured to bias the ring or tip of the mic connector. Some experimentation may be required to determine the proper setting for each different mic. The bias voltage is generated with a resistor divider from the main supply voltage and is 0.66*Vcc. The input stage is a single amp with a gain of 4.7 driving a volume control pot. An isolation resistor is required due to the capacitive nature of the slide pots resulting in a 0.8*4.7 or 3.8 max gain. the main gain stage is after the level control pot and can be adjusted for gains of 2 to 22. This makes the maximum mic gain 4.7*0.8*22 = 83. 47 pF bandwidth limiting caps are placed across the feedback resistors on the gain stages of the mic interface. This is a technique designed to prevent oscillation in high gain and capacitive loading circuits of which this has both. The output stage for each channel is a unity gain summing amp that adds the signal from the line inputs to the signal from the mic according to the ratio set by the level control pots. Bandwidth limiting caps are again used to help stabilize the outputs that could be driving unknown but possibly very capacitive loads.
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SLOU009
4. Layout
NOTE: Layouts are not to scale.
Operating the Mic Mixer Evaluation Module (SLOP107)
11
12
SLOU009
5. Bill of Materials
File: micmixer.xls Date: 03/05/97
Ref Des C1 C2 C3 C4 C5 C6 C7 C8 C9 C10 C11 C12 J1 J2 J3 J4 J5 J6 JP1 JP2 R1 R2 R3 R4 R5 R6 R7 R8 R9 R10 R11 R12 R13 R14 R15 R16 R17 R18 R19 R20 R21 R22 R23 R24 R25 U1 U2 PCB
Part No. C3216Y5V1C105Z PCC470CCT-ND C3225Y5V1C106Z PCC470CCT-ND C3216Y5V1C105Z PCC470CCT-ND C3216Y5V1C225Z C3216Y5V1C225Z C3216Y5V1C105Z PCC104BCT-ND PCC470CCT-ND PCC104BCT-ND 161-3504
448XC3503BAN 448XC3503BAN
3362P-200K 448XC3503BAN
TLC2274CD TLC2274CD SLOP107
Description Capacitor, Ceramic, 1.0 uF, 16V, Y5V, 1206 Capacitor, Ceramic, 47 pF, 50V, NPO, 1206 Capacitor, Ceramic, 10 uF, 16V, Y5V, 1206 Capacitor, Ceramic, 47 pF, 50V, NPO, 1206 Capacitor, Ceramic, 1.0 uF, 16V, Y5V, 1206 Capacitor, Ceramic, 47 pF, 50V, NPO, 1206 Capacitor, Ceramic, 2.2 uF, 16V, Y5V, 1206 Capacitor, Ceramic, 2.2 uF, 16V, Y5V, 1206 Capacitor, Ceramic, 1.0 uF, 16V, Y5V, 1206 Capacitor, Ceramic, 0.1 uF, 50V, X7R, 1206 Capacitor, Ceramic, 47 pF, 50V, NPO, 1206 Capacitor, Ceramic, 0.1 uF, 50V, X7R, 1206 Header, 2-pin, 0.025"-sq, 100-mil centers Phone Jack, Stereo, 1/8" Header, 2-pin, 0.025"-sq, 100-mil centers Header, 2-pin, 0.025"-sq, 100-mil centers Header, 2-pin, 0.025"-sq, 100-mil centers Header, 2-pin, 0.025"-sq, 100-mil centers Header, 3-pin, 0.025"-sq, 100-mil centers Header, 2-pin, 0.025"-sq, 100-mil centers Potientiometer, 50K Ohm, Slide, Audio taper, 1.4" Potientiometer, 50K Ohm, Slide, Audio taper, 1.4" Resistor, CF, 10K Ohm, 1/8 W, 5 %, 1206 Resistor, CF, 20K Ohm, 1/8 W, 5 %, 1206 Resistor, CF, 10K Ohm, 1/8 W, 5 %, 1206 Resistor, CF, 20K Ohm, 1/8 W, 5 %, 1206 Resistor, CF, 2.2K Ohm, 1/8 W, 5 %, 1206 Resistor, CF, 10K Ohm, 1/8 W, 5 %, 1206 Resistor, CF, 47K Ohm, 1/8 W, 5 %, 1206 Potientiometer, 200K Ohm, 1-turn, 1/4"-sq Potientiometer, 50K Ohm, Slide, Audio taper, 1.4" Resistor, CF, 10K Ohm, 1/8 W, 5 %, 1206 Resistor, CF, 20K Ohm, 1/8 W, 5 %, 1206 Resistor, CF, 10K Ohm, 1/8 W, 5 %, 1206 Resistor, CF, 20K Ohm, 1/8 W, 5 %, 1206 Resistor, CF, 10K Ohm, 1/8 W, 5 %, 1206 Resistor, CF, 10K Ohm, 1/8 W, 5 %, 1206 Resistor, CF, 10K Ohm, 1/8 W, 5 %, 1206 Resistor, CF, 10K Ohm, 1/8 W, 5 %, 1206 Resistor, CF, 10K Ohm, 1/8 W, 5 %, 1206 Resistor, CF, 10K Ohm, 1/8 W, 5 %, 1206 Resistor, CF, 20K Ohm, 1/8 W, 5 %, 1206 Resistor, CF, 20K Ohm, 1/8 W, 5 %, 1206 Resistor, CF, 20K Ohm, 1/8 W, 5 %, 1206 Resistor, CF, 10K Ohm, 1/8 W, 5 %, 1206 IC,Quad Op Amp, RRO, 2 MHz, SO-14 IC,Quad Op Amp, RRO, 2 MHz, SO-14 Printed Circuit Board, 2-layer
Source TDK Digikey TDK Digikey TDK Digikey TDK TDK TDK Digikey Digikey Digikey Mouser
Page 245 245 245
245 245 245 92
CTS CTS
CTS
TI TI TI
Operating the Mic Mixer Evaluation Module (SLOP107)
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