EESchema Schematic File Version 2
LIBS:power
LIBS:device
LIBS:transistors
LIBS:conn
LIBS:linear
LIBS:regul
LIBS:74xx
LIBS:cmos4000
LIBS:adc-dac
LIBS:memory
LIBS:xilinx
LIBS:microcontrollers
LIBS:dsp
LIBS:microchip
LIBS:analog_switches
LIBS:motorola
LIBS:texas
LIBS:intel
LIBS:audio
LIBS:interface
LIBS:digital-audio
LIBS:philips
LIBS:display
LIBS:cypress
LIBS:siliconi
LIBS:opto
LIBS:atmel
LIBS:contrib
LIBS:valves
LIBS:nocko
LIBS:bmi-8ch-cache
EELAYER 25 0
EELAYER END
$Descr USLetter 11000 8500
encoding utf-8
Sheet 3 5
Title "Input Channel 2 & 3"
Date "2017-03-23"
Rev "AA"
Comp "Monadnock Systems"
Comment1 ""
Comment2 ""
Comment3 ""
Comment4 ""
$EndDescr
$Comp
L R R301
U 1 1 58D6CE0B
P 1400 1200
F 0 "R301" V 1480 1200 50  0000 C CNN
F 1 "DNP" V 1400 1200 50  0000 C CNN
F 2 "" V 1330 1200 50  0001 C CNN
F 3 "" H 1400 1200 50  0001 C CNN
	1    1400 1200
	1    0    0    -1  
$EndComp
$Comp
L R R307
U 1 1 58D6CE0C
P 1400 1800
F 0 "R307" V 1480 1800 50  0000 C CNN
F 1 "2M" V 1400 1800 50  0000 C CNN
F 2 "" V 1330 1800 50  0001 C CNN
F 3 "" H 1400 1800 50  0001 C CNN
	1    1400 1800
	1    0    0    -1  
$EndComp
$Comp
L R R308
U 1 1 58D6CE0D
P 1750 1800
F 0 "R308" V 1830 1800 50  0000 C CNN
F 1 "2M" V 1750 1800 50  0000 C CNN
F 2 "" V 1680 1800 50  0001 C CNN
F 3 "" H 1750 1800 50  0001 C CNN
	1    1750 1800
	1    0    0    -1  
$EndComp
$Comp
L R R302
U 1 1 58D6CE0E
P 1750 1200
F 0 "R302" V 1830 1200 50  0000 C CNN
F 1 "2M" V 1750 1200 50  0000 C CNN
F 2 "" V 1680 1200 50  0001 C CNN
F 3 "" H 1750 1200 50  0001 C CNN
	1    1750 1200
	1    0    0    -1  
$EndComp
$Comp
L CONN_01X02 J301
U 1 1 58D6CE0F
P 900 1200
F 0 "J301" H 900 1350 50  0000 C CNN
F 1 "Sensor" V 1000 1200 50  0000 C CNN
F 2 "" H 900 1200 50  0001 C CNN
F 3 "" H 900 1200 50  0001 C CNN
	1    900  1200
	-1   0    0    -1  
$EndComp
$Comp
L GNDA #PWR029
U 1 1 58D6CE10
P 1600 2050
F 0 "#PWR029" H 1600 1800 50  0001 C CNN
F 1 "GNDA" H 1600 1900 50  0000 C CNN
F 2 "" H 1600 2050 50  0001 C CNN
F 3 "" H 1600 2050 50  0001 C CNN
	1    1600 2050
	1    0    0    -1  
$EndComp
Text GLabel 1600 900  1    60   Input ~ 0
Vref
Text Label 1050 1500 0    60   ~ 0
A
Text Label 1900 1500 2    60   ~ 0
B
Text Label 1850 1400 0    60   ~ 0
A
$Comp
L GNDA #PWR030
U 1 1 58D6CE11
P 3250 1900
F 0 "#PWR030" H 3250 1650 50  0001 C CNN
F 1 "GNDA" H 3250 1750 50  0000 C CNN
F 2 "" H 3250 1900 50  0001 C CNN
F 3 "" H 3250 1900 50  0001 C CNN
	1    3250 1900
	1    0    0    -1  
$EndComp
Text GLabel 3600 1900 2    60   Input ~ 0
Vref/2
$Comp
L C C305
U 1 1 58D6CE12
P 2200 1400
F 0 "C305" V 2250 1450 50  0000 L CNN
F 1 "1µF" V 2050 1300 50  0000 L CNN
F 2 "" H 2238 1250 50  0001 C CNN
F 3 "" H 2200 1400 50  0001 C CNN
	1    2200 1400
	0    1    1    0   
$EndComp
$Comp
L C C307
U 1 1 58D6CE13
P 2200 1800
F 0 "C307" V 2150 1850 50  0000 L CNN
F 1 "1µF" V 2350 1700 50  0000 L CNN
F 2 "" H 2238 1650 50  0001 C CNN
F 3 "" H 2200 1800 50  0001 C CNN
	1    2200 1800
	0    1    1    0   
$EndComp
Text Notes 1950 1000 0    60   ~ 0
Optional AC Coupling\n3dB down @ 0.4Hz
$Comp
L AD8622 U302
U 1 1 58D6CE14
P 6950 1700
F 0 "U302" H 7150 1850 50  0000 L CNN
F 1 "AD8622" H 7150 1550 50  0000 L CNN
F 2 "" H 6950 1700 50  0001 C CNN
F 3 "" H 6950 1700 50  0001 C CNN
	1    6950 1700
	1    0    0    -1  
$EndComp
$Comp
L C C306
U 1 1 58D6CE15
P 6250 1750
F 0 "C306" H 6275 1850 50  0000 L CNN
F 1 "910pF" H 6150 1650 50  0000 L CNN
F 2 "" H 6288 1600 50  0001 C CNN
F 3 "" H 6250 1750 50  0001 C CNN
	1    6250 1750
	1    0    0    -1  
$EndComp
$Comp
L C C304
U 1 1 58D6CE16
P 6600 1150
F 0 "C304" V 6550 1200 50  0000 L CNN
F 1 "9.1nF" V 6650 1200 50  0000 L CNN
F 2 "" H 6638 1000 50  0001 C CNN
F 3 "" H 6600 1150 50  0001 C CNN
	1    6600 1150
	0    1    1    0   
$EndComp
$Comp
L R R306
U 1 1 58D6CE17
P 6000 1600
F 0 "R306" V 6080 1600 50  0000 C CNN
F 1 "1.15M" V 6000 1600 39  0000 C CNN
F 2 "" V 5930 1600 50  0001 C CNN
F 3 "" H 6000 1600 50  0001 C CNN
	1    6000 1600
	0    1    1    0   
$EndComp
$Comp
L R R305
U 1 1 58D6CE18
P 5600 1600
F 0 "R305" V 5680 1600 50  0000 C CNN
F 1 "86.6k" V 5600 1600 50  0000 C CNN
F 2 "" V 5530 1600 50  0001 C CNN
F 3 "" H 5600 1600 50  0001 C CNN
	1    5600 1600
	0    1    1    0   
$EndComp
$Comp
L GNDA #PWR031
U 1 1 58D6CE19
P 6250 1900
F 0 "#PWR031" H 6250 1650 50  0001 C CNN
F 1 "GNDA" H 6250 1750 50  0000 C CNN
F 2 "" H 6250 1900 50  0001 C CNN
F 3 "" H 6250 1900 50  0001 C CNN
	1    6250 1900
	1    0    0    -1  
$EndComp
Text Notes 750  5450 0    87   ~ 0
Notes:\nDesigned for 0-5V Output\nOutput can swing from AGND to VBATT (5.125-12V) in some failure modes.\nMay damage ADC if input range is <= VBATT\n\nR204, R213: 0.1%\nR208, R209: 1%\nR202, R205, R206 & R203, R207: Metal Foil / Thin Film (Resistor packs preferred)\nALL C: 5%, 16V
$Comp
L R R309
U 1 1 58D6CE1A
P 2500 1800
F 0 "R309" V 2580 1800 50  0000 C CNN
F 1 "390k" V 2500 1800 50  0000 C CNN
F 2 "" V 2430 1800 50  0001 C CNN
F 3 "" H 2500 1800 50  0001 C CNN
	1    2500 1800
	1    0    0    -1  
$EndComp
$Comp
L R R303
U 1 1 58D6CE1B
P 2500 1400
F 0 "R303" V 2580 1400 50  0000 C CNN
F 1 "390k" V 2500 1400 50  0000 C CNN
F 2 "" V 2430 1400 50  0001 C CNN
F 3 "" H 2500 1400 50  0001 C CNN
	1    2500 1400
	1    0    0    -1  
$EndComp
Text GLabel 2400 1600 0    60   Input ~ 0
Vref/2
$Comp
L GNDA #PWR032
U 1 1 58D6CE1C
P 9900 1150
F 0 "#PWR032" H 9900 900 50  0001 C CNN
F 1 "GNDA" H 9900 1000 50  0000 C CNN
F 2 "" H 9900 1150 50  0001 C CNN
F 3 "" H 9900 1150 50  0001 C CNN
	1    9900 1150
	1    0    0    -1  
$EndComp
$Comp
L C C302
U 1 1 58D6CE1D
P 9900 1000
F 0 "C302" H 9925 1100 50  0000 L CNN
F 1 "0.1μF" H 9925 900 50  0000 L CNN
F 2 "" H 9938 850 50  0001 C CNN
F 3 "" H 9900 1000 50  0001 C CNN
	1    9900 1000
	1    0    0    -1  
$EndComp
Text Notes 5300 2450 0    60   ~ 0
Chebyshev (0.23dB)\n-3dB @ 195Hz\n-50dB @ 3.1kHz
$Comp
L VBATT #PWR033
U 1 1 58D6CE1E
P 6900 1450
F 0 "#PWR033" H 6900 1300 50  0001 C CNN
F 1 "VBATT" H 6900 1600 50  0000 C CNN
F 2 "" H 6900 1450 50  0000 C CNN
F 3 "" H 6900 1450 50  0000 C CNN
	1    6900 1450
	1    0    0    -1  
$EndComp
$Comp
L GNDA #PWR034
U 1 1 58D6CE1F
P 6900 1950
F 0 "#PWR034" H 6900 1700 50  0001 C CNN
F 1 "GNDA" H 6900 1800 50  0000 C CNN
F 2 "" H 6900 1950 50  0001 C CNN
F 3 "" H 6900 1950 50  0001 C CNN
	1    6900 1950
	1    0    0    -1  
$EndComp
$Comp
L AD8227 U301
U 1 1 58D6CE20
P 3250 1600
F 0 "U301" H 3400 1725 50  0000 L CNN
F 1 "AD8227" H 3400 1475 50  0000 L CNN
F 2 "" H 3350 1600 50  0001 C CNN
F 3 "" H 3350 1600 50  0001 C CNN
	1    3250 1600
	1    0    0    -1  
$EndComp
$Comp
L R_Small R304
U 1 1 58D6CE21
P 2850 1600
F 0 "R304" V 2900 1500 50  0000 L CNN
F 1 "1.78k" V 2845 1535 31  0000 L CNN
F 2 "" H 2850 1600 50  0001 C CNN
F 3 "" H 2850 1600 50  0001 C CNN
	1    2850 1600
	1    0    0    -1  
$EndComp
Text Notes 2750 1450 0    39   ~ 0
G=50
$Comp
L VBATT #PWR035
U 1 1 58D6CE22
P 3250 1300
F 0 "#PWR035" H 3250 1150 50  0001 C CNN
F 1 "VBATT" H 3250 1450 50  0000 C CNN
F 2 "" H 3250 1300 50  0000 C CNN
F 3 "" H 3250 1300 50  0000 C CNN
	1    3250 1300
	1    0    0    -1  
$EndComp
Wire Wire Line
	1200 1250 1200 1500
Wire Wire Line
	1200 1250 1100 1250
Connection ~ 1400 1500
Wire Wire Line
	1100 1150 1100 1050
Wire Wire Line
	1100 1050 1750 1050
Connection ~ 1400 1050
Wire Wire Line
	1600 1050 1600 900 
Connection ~ 1600 1050
Wire Wire Line
	1400 1950 1750 1950
Wire Wire Line
	1600 1950 1600 2050
Connection ~ 1600 1950
Connection ~ 1200 1500
Wire Wire Line
	1050 1500 1400 1500
Wire Wire Line
	1400 1350 1400 1650
Wire Wire Line
	1750 1350 1750 1650
Wire Wire Line
	1900 1500 1900 1800
Wire Wire Line
	1850 1400 2050 1400
Wire Notes Line
	2050 1100 2700 1100
Wire Wire Line
	6650 1800 6500 1800
Wire Wire Line
	6500 1800 6500 2200
Wire Wire Line
	7600 1150 7600 2200
Wire Wire Line
	7250 1700 9000 1700
Wire Wire Line
	5750 1600 5850 1600
Wire Wire Line
	6150 1600 6650 1600
Connection ~ 6250 1600
Wire Wire Line
	5800 1600 5800 1150
Wire Wire Line
	5800 1150 6450 1150
Connection ~ 5800 1600
Wire Wire Line
	7600 1150 6750 1150
Connection ~ 7600 1700
Wire Notes Line
	5250 1000 8350 1000
Wire Notes Line
	8350 1000 8350 2450
Wire Notes Line
	5250 2450 5250 1000
Wire Wire Line
	7600 2200 6500 2200
Wire Wire Line
	2350 1250 2750 1250
Wire Wire Line
	2350 1250 2350 1400
Connection ~ 2500 1250
Wire Wire Line
	2350 1800 2350 1950
Wire Wire Line
	2500 1550 2500 1650
Wire Wire Line
	2400 1600 2500 1600
Connection ~ 2500 1600
Wire Wire Line
	1900 1800 2050 1800
Wire Wire Line
	2350 1950 2750 1950
Connection ~ 2500 1950
Wire Notes Line
	2050 2100 2700 2100
Wire Notes Line
	2700 2100 2700 1100
Wire Notes Line
	2050 1100 2050 2100
Connection ~ 9900 1150
Connection ~ 9900 850 
Wire Notes Line
	8350 2450 5250 2450
Wire Wire Line
	3600 1900 3350 1900
Wire Wire Line
	2750 1250 2950 1400
Wire Wire Line
	2750 1950 2950 1800
Wire Wire Line
	3650 1600 5450 1600
Wire Wire Line
	2950 1500 2850 1500
Wire Wire Line
	2950 1700 2850 1700
Connection ~ 1750 1500
Wire Wire Line
	1750 1500 1900 1500
Text Notes 1950 1050 0    39   ~ 0
When DC coupled, sensor failure grounds output.
Text Notes 2750 2350 0    39   ~ 0
CMRR: >95dB\nInput Voltage Noise Density: <28nV/√Hz\nOutput Voltage Noise Density: <330nV/√Hz\nVoltage Noise (0.1-10Hz): < 0.8μV p-p\n
Text Notes 7150 2400 0    39   ~ 0
Offset: <125uV\nOffset Drift: <1.3uv/°C\nVoltage Noise Density: 12nV/√Hz\nVoltage Noise (0.1-10Hz): 0.2μV p-p
Text Notes 7650 1100 0    60   ~ 0
Antialias Filter
$Comp
L C C303
U 1 1 58D6CE23
P 10150 1000
F 0 "C303" H 10175 1100 50  0000 L CNN
F 1 "10μF" H 10175 900 50  0000 L CNN
F 2 "" H 10188 850 50  0001 C CNN
F 3 "" H 10150 1000 50  0001 C CNN
	1    10150 1000
	1    0    0    -1  
$EndComp
Wire Wire Line
	9650 1150 10150 1150
Wire Wire Line
	9650 850  10150 850 
$Comp
L VBATT #PWR036
U 1 1 58D6CE24
P 9900 850
F 0 "#PWR036" H 9900 700 50  0001 C CNN
F 1 "VBATT" H 9900 1000 50  0000 C CNN
F 2 "" H 9900 850 50  0000 C CNN
F 3 "" H 9900 850 50  0000 C CNN
	1    9900 850 
	1    0    0    -1  
$EndComp
Text Notes 6950 5250 0    60   ~ 0
Assumptions:\n - (Initial) DAQ is MCC USB-1208FS (available at BMI)\n     11-bit, max 6250 S/sec for each channel; sequential\n - Target Bandwidth: 195Hz\n - Sampling Rate 6240 S/s\n - Sensor resistance ~2MΩ\n - Respiration motion changes sensor resistance by < -+10%
Text Notes 7000 6400 0    60   ~ 0
Analysis Notes:\n\n  1. Steep digital filter 0.4-175Hz\n    - Respiration typically 0.25-0.33Hz\n    - Narrower useful bandwidth likely, modeling needed.\n\n  2. Correct for temporal offset of sample due to sequential sampling.\n\n  3. 2x decimation for 13-bit (ENOB) and noise reduction
Text Notes 750  7750 0    60   ~ 0
Open Questions:\n\n1. Trimming the bridge.\n  - Only makes sense w/ DC coupling\n  - Bad tempco\n  - Bad UX\n  - Needed for significant gain\n\n2. AC vs DC Coupling; both have advantages: AC is easier\n\n3. Reducing R202,R203,R206,R207 to decrease Johnson noise: Probably useless.\n  - Changing R202,R206 may break INAMP CMRR\n\n4. Use chopper amps in signal path: Probably bad\n  - Lower total noise for *extremely* small bandwidths (<5Hz?)\n  - Lower offset (if DC coupled)\n\n5. Driven shields for output: Probably useless\n  - Reduce error due to leakage current\n  - No analysis done to determine if this is significant\n  - Current DAQ isn't likely to benefit
$Comp
L CONN_01X02 J302
U 1 1 58D6CE25
P 9200 1750
F 0 "J302" H 9200 1900 50  0000 C CNN
F 1 "Channel 0" V 9300 1750 50  0000 C CNN
F 2 "" H 9200 1750 50  0001 C CNN
F 3 "" H 9200 1750 50  0001 C CNN
	1    9200 1750
	1    0    0    1   
$EndComp
$Comp
L GNDA #PWR037
U 1 1 58D6CE26
P 9000 1800
F 0 "#PWR037" H 9000 1550 50  0001 C CNN
F 1 "GNDA" H 9000 1650 50  0000 C CNN
F 2 "" H 9000 1800 50  0001 C CNN
F 3 "" H 9000 1800 50  0001 C CNN
	1    9000 1800
	1    0    0    -1  
$EndComp
$Comp
L C C301
U 1 1 58D6CE27
P 9650 1000
F 0 "C301" H 9675 1100 50  0000 L CNN
F 1 "0.1μF" H 9675 900 50  0000 L CNN
F 2 "" H 9688 850 50  0001 C CNN
F 3 "" H 9650 1000 50  0001 C CNN
	1    9650 1000
	1    0    0    -1  
$EndComp
$Comp
L R R310
U 1 1 58D6CE28
P 1400 3050
F 0 "R310" V 1480 3050 50  0000 C CNN
F 1 "DNP" V 1400 3050 50  0000 C CNN
F 2 "" V 1330 3050 50  0001 C CNN
F 3 "" H 1400 3050 50  0001 C CNN
	1    1400 3050
	1    0    0    -1  
$EndComp
$Comp
L R R316
U 1 1 58D6CE29
P 1400 3650
F 0 "R316" V 1480 3650 50  0000 C CNN
F 1 "2M" V 1400 3650 50  0000 C CNN
F 2 "" V 1330 3650 50  0001 C CNN
F 3 "" H 1400 3650 50  0001 C CNN
	1    1400 3650
	1    0    0    -1  
$EndComp
$Comp
L R R317
U 1 1 58D6CE2A
P 1750 3650
F 0 "R317" V 1830 3650 50  0000 C CNN
F 1 "2M" V 1750 3650 50  0000 C CNN
F 2 "" V 1680 3650 50  0001 C CNN
F 3 "" H 1750 3650 50  0001 C CNN
	1    1750 3650
	1    0    0    -1  
$EndComp
$Comp
L R R311
U 1 1 58D6CE2B
P 1750 3050
F 0 "R311" V 1830 3050 50  0000 C CNN
F 1 "2M" V 1750 3050 50  0000 C CNN
F 2 "" V 1680 3050 50  0001 C CNN
F 3 "" H 1750 3050 50  0001 C CNN
	1    1750 3050
	1    0    0    -1  
$EndComp
$Comp
L CONN_01X02 J303
U 1 1 58D6CE2C
P 900 3050
F 0 "J303" H 900 3200 50  0000 C CNN
F 1 "Sensor" V 1000 3050 50  0000 C CNN
F 2 "" H 900 3050 50  0001 C CNN
F 3 "" H 900 3050 50  0001 C CNN
	1    900  3050
	-1   0    0    -1  
$EndComp
$Comp
L GNDA #PWR038
U 1 1 58D6CE2D
P 1600 3900
F 0 "#PWR038" H 1600 3650 50  0001 C CNN
F 1 "GNDA" H 1600 3750 50  0000 C CNN
F 2 "" H 1600 3900 50  0001 C CNN
F 3 "" H 1600 3900 50  0001 C CNN
	1    1600 3900
	1    0    0    -1  
$EndComp
Text GLabel 1600 2750 1    60   Input ~ 0
Vref
Text Label 1050 3350 0    60   ~ 0
A
Text Label 1900 3350 2    60   ~ 0
B
Text Label 1850 3250 0    60   ~ 0
A
$Comp
L GNDA #PWR039
U 1 1 58D6CE2E
P 3250 3750
F 0 "#PWR039" H 3250 3500 50  0001 C CNN
F 1 "GNDA" H 3250 3600 50  0000 C CNN
F 2 "" H 3250 3750 50  0001 C CNN
F 3 "" H 3250 3750 50  0001 C CNN
	1    3250 3750
	1    0    0    -1  
$EndComp
Text GLabel 3600 3750 2    60   Input ~ 0
Vref/2
$Comp
L C C309
U 1 1 58D6CE2F
P 2200 3250
F 0 "C309" V 2250 3300 50  0000 L CNN
F 1 "1µF" V 2050 3150 50  0000 L CNN
F 2 "" H 2238 3100 50  0001 C CNN
F 3 "" H 2200 3250 50  0001 C CNN
	1    2200 3250
	0    1    1    0   
$EndComp
$Comp
L C C311
U 1 1 58D6CE30
P 2200 3650
F 0 "C311" V 2150 3700 50  0000 L CNN
F 1 "1µF" V 2350 3550 50  0000 L CNN
F 2 "" H 2238 3500 50  0001 C CNN
F 3 "" H 2200 3650 50  0001 C CNN
	1    2200 3650
	0    1    1    0   
$EndComp
Text Notes 1950 2850 0    60   ~ 0
Optional AC Coupling\n3dB down @ 0.4Hz
$Comp
L AD8622 U302
U 2 1 58D6CE31
P 6950 3550
F 0 "U302" H 7150 3700 50  0000 L CNN
F 1 "AD8622" H 7150 3400 50  0000 L CNN
F 2 "" H 6950 3550 50  0001 C CNN
F 3 "" H 6950 3550 50  0001 C CNN
	2    6950 3550
	1    0    0    -1  
$EndComp
$Comp
L C C310
U 1 1 58D6CE32
P 6250 3600
F 0 "C310" H 6275 3700 50  0000 L CNN
F 1 "910pF" H 6150 3500 50  0000 L CNN
F 2 "" H 6288 3450 50  0001 C CNN
F 3 "" H 6250 3600 50  0001 C CNN
	1    6250 3600
	1    0    0    -1  
$EndComp
$Comp
L C C308
U 1 1 58D6CE33
P 6600 3000
F 0 "C308" V 6550 3050 50  0000 L CNN
F 1 "9.1nF" V 6650 3050 50  0000 L CNN
F 2 "" H 6638 2850 50  0001 C CNN
F 3 "" H 6600 3000 50  0001 C CNN
	1    6600 3000
	0    1    1    0   
$EndComp
$Comp
L R R315
U 1 1 58D6CE34
P 6000 3450
F 0 "R315" V 6080 3450 50  0000 C CNN
F 1 "1.15M" V 6000 3450 39  0000 C CNN
F 2 "" V 5930 3450 50  0001 C CNN
F 3 "" H 6000 3450 50  0001 C CNN
	1    6000 3450
	0    1    1    0   
$EndComp
$Comp
L R R314
U 1 1 58D6CE35
P 5600 3450
F 0 "R314" V 5680 3450 50  0000 C CNN
F 1 "86.6k" V 5600 3450 50  0000 C CNN
F 2 "" V 5530 3450 50  0001 C CNN
F 3 "" H 5600 3450 50  0001 C CNN
	1    5600 3450
	0    1    1    0   
$EndComp
$Comp
L GNDA #PWR040
U 1 1 58D6CE36
P 6250 3750
F 0 "#PWR040" H 6250 3500 50  0001 C CNN
F 1 "GNDA" H 6250 3600 50  0000 C CNN
F 2 "" H 6250 3750 50  0001 C CNN
F 3 "" H 6250 3750 50  0001 C CNN
	1    6250 3750
	1    0    0    -1  
$EndComp
$Comp
L R R318
U 1 1 58D6CE37
P 2500 3650
F 0 "R318" V 2580 3650 50  0000 C CNN
F 1 "390k" V 2500 3650 50  0000 C CNN
F 2 "" V 2430 3650 50  0001 C CNN
F 3 "" H 2500 3650 50  0001 C CNN
	1    2500 3650
	1    0    0    -1  
$EndComp
$Comp
L R R312
U 1 1 58D6CE38
P 2500 3250
F 0 "R312" V 2580 3250 50  0000 C CNN
F 1 "390k" V 2500 3250 50  0000 C CNN
F 2 "" V 2430 3250 50  0001 C CNN
F 3 "" H 2500 3250 50  0001 C CNN
	1    2500 3250
	1    0    0    -1  
$EndComp
Text GLabel 2400 3450 0    60   Input ~ 0
Vref/2
Text Notes 5300 4300 0    60   ~ 0
Chebyshev (0.23dB)\n-3dB @ 195Hz\n-50dB @ 3.1kHz
$Comp
L VBATT #PWR041
U 1 1 58D6CE39
P 6900 3300
F 0 "#PWR041" H 6900 3150 50  0001 C CNN
F 1 "VBATT" H 6900 3450 50  0000 C CNN
F 2 "" H 6900 3300 50  0000 C CNN
F 3 "" H 6900 3300 50  0000 C CNN
	1    6900 3300
	1    0    0    -1  
$EndComp
$Comp
L GNDA #PWR042
U 1 1 58D6CE3A
P 6900 3800
F 0 "#PWR042" H 6900 3550 50  0001 C CNN
F 1 "GNDA" H 6900 3650 50  0000 C CNN
F 2 "" H 6900 3800 50  0001 C CNN
F 3 "" H 6900 3800 50  0001 C CNN
	1    6900 3800
	1    0    0    -1  
$EndComp
$Comp
L AD8227 U303
U 1 1 58D6CE3B
P 3250 3450
F 0 "U303" H 3400 3575 50  0000 L CNN
F 1 "AD8227" H 3400 3325 50  0000 L CNN
F 2 "" H 3350 3450 50  0001 C CNN
F 3 "" H 3350 3450 50  0001 C CNN
	1    3250 3450
	1    0    0    -1  
$EndComp
$Comp
L R_Small R313
U 1 1 58D6CE3C
P 2850 3450
F 0 "R313" V 2900 3350 50  0000 L CNN
F 1 "1.78k" V 2845 3385 31  0000 L CNN
F 2 "" H 2850 3450 50  0001 C CNN
F 3 "" H 2850 3450 50  0001 C CNN
	1    2850 3450
	1    0    0    -1  
$EndComp
Text Notes 2750 3300 0    39   ~ 0
G=50
$Comp
L VBATT #PWR043
U 1 1 58D6CE3D
P 3250 3150
F 0 "#PWR043" H 3250 3000 50  0001 C CNN
F 1 "VBATT" H 3250 3300 50  0000 C CNN
F 2 "" H 3250 3150 50  0000 C CNN
F 3 "" H 3250 3150 50  0000 C CNN
	1    3250 3150
	1    0    0    -1  
$EndComp
Wire Wire Line
	1200 3100 1200 3350
Wire Wire Line
	1200 3100 1100 3100
Connection ~ 1400 3350
Wire Wire Line
	1100 3000 1100 2900
Wire Wire Line
	1100 2900 1750 2900
Connection ~ 1400 2900
Wire Wire Line
	1600 2900 1600 2750
Connection ~ 1600 2900
Wire Wire Line
	1400 3800 1750 3800
Wire Wire Line
	1600 3800 1600 3900
Connection ~ 1600 3800
Connection ~ 1200 3350
Wire Wire Line
	1050 3350 1400 3350
Wire Wire Line
	1400 3200 1400 3500
Wire Wire Line
	1750 3200 1750 3500
Wire Wire Line
	1900 3350 1900 3650
Wire Wire Line
	1850 3250 2050 3250
Wire Notes Line
	2050 2950 2700 2950
Wire Wire Line
	6650 3650 6500 3650
Wire Wire Line
	6500 3650 6500 4050
Wire Wire Line
	7600 3000 7600 4050
Wire Wire Line
	7250 3550 9000 3550
Wire Wire Line
	5750 3450 5850 3450
Wire Wire Line
	6150 3450 6650 3450
Connection ~ 6250 3450
Wire Wire Line
	5800 3450 5800 3000
Wire Wire Line
	5800 3000 6450 3000
Connection ~ 5800 3450
Wire Wire Line
	7600 3000 6750 3000
Connection ~ 7600 3550
Wire Notes Line
	5250 2850 8350 2850
Wire Notes Line
	8350 2850 8350 4300
Wire Notes Line
	5250 4300 5250 2850
Wire Wire Line
	7600 4050 6500 4050
Wire Wire Line
	2350 3100 2750 3100
Wire Wire Line
	2350 3100 2350 3250
Connection ~ 2500 3100
Wire Wire Line
	2350 3650 2350 3800
Wire Wire Line
	2500 3400 2500 3500
Wire Wire Line
	2400 3450 2500 3450
Connection ~ 2500 3450
Wire Wire Line
	1900 3650 2050 3650
Wire Wire Line
	2350 3800 2750 3800
Connection ~ 2500 3800
Wire Notes Line
	2050 3950 2700 3950
Wire Notes Line
	2700 3950 2700 2950
Wire Notes Line
	2050 2950 2050 3950
Wire Notes Line
	8350 4300 5250 4300
Wire Wire Line
	3600 3750 3350 3750
Wire Wire Line
	2750 3100 2950 3250
Wire Wire Line
	2750 3800 2950 3650
Wire Wire Line
	3650 3450 5450 3450
Wire Wire Line
	2950 3350 2850 3350
Wire Wire Line
	2950 3550 2850 3550
Connection ~ 1750 3350
Wire Wire Line
	1750 3350 1900 3350
Text Notes 1950 2900 0    39   ~ 0
When DC coupled, sensor failure grounds output.
Text Notes 2750 4200 0    39   ~ 0
CMRR: >95dB\nInput Voltage Noise Density: <28nV/√Hz\nOutput Voltage Noise Density: <330nV/√Hz\nVoltage Noise (0.1-10Hz): < 0.8μV p-p\n
Text Notes 7150 4250 0    39   ~ 0
Offset: <125uV\nOffset Drift: <1.3uv/°C\nVoltage Noise Density: 12nV/√Hz\nVoltage Noise (0.1-10Hz): 0.2μV p-p
Text Notes 7650 2950 0    60   ~ 0
Antialias Filter
$Comp
L CONN_01X02 J304
U 1 1 58D6CE3E
P 9200 3600
F 0 "J304" H 9200 3750 50  0000 C CNN
F 1 "Channel 1" V 9300 3600 50  0000 C CNN
F 2 "" H 9200 3600 50  0001 C CNN
F 3 "" H 9200 3600 50  0001 C CNN
	1    9200 3600
	1    0    0    1   
$EndComp
$Comp
L GNDA #PWR044
U 1 1 58D6CE3F
P 9000 3650
F 0 "#PWR044" H 9000 3400 50  0001 C CNN
F 1 "GNDA" H 9000 3500 50  0000 C CNN
F 2 "" H 9000 3650 50  0001 C CNN
F 3 "" H 9000 3650 50  0001 C CNN
	1    9000 3650
	1    0    0    -1  
$EndComp
Text Notes 3500 5950 0    60   ~ 0
Problems:\n\n  - AD8622 isn't RRIO; will saturate at (V+)-1.2V.\n      Near the end of battery life; this could be less that 5V.
$EndSCHEMATC