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 2 2
Title "Input Channel 0"
Date "2017-03-23"
Rev "AA"
Comp "Monadnock Systems"
Comment1 ""
Comment2 ""
Comment3 ""
Comment4 ""
$EndDescr
$Comp
L R R201
U 1 1 58D46487
P 3650 2900
F 0 "R201" V 3730 2900 50  0000 C CNN
F 1 "DNP" V 3650 2900 50  0000 C CNN
F 2 "" V 3580 2900 50  0001 C CNN
F 3 "" H 3650 2900 50  0001 C CNN
	1    3650 2900
	1    0    0    -1  
$EndComp
$Comp
L R R205
U 1 1 58D46589
P 3650 3500
F 0 "R205" V 3730 3500 50  0000 C CNN
F 1 "2M" V 3650 3500 50  0000 C CNN
F 2 "" V 3580 3500 50  0001 C CNN
F 3 "" H 3650 3500 50  0001 C CNN
	1    3650 3500
	1    0    0    -1  
$EndComp
$Comp
L R R206
U 1 1 58D465AD
P 4000 3500
F 0 "R206" V 4080 3500 50  0000 C CNN
F 1 "2M" V 4000 3500 50  0000 C CNN
F 2 "" V 3930 3500 50  0001 C CNN
F 3 "" H 4000 3500 50  0001 C CNN
	1    4000 3500
	1    0    0    -1  
$EndComp
$Comp
L R R202
U 1 1 58D465DB
P 4000 2900
F 0 "R202" V 4080 2900 50  0000 C CNN
F 1 "2M" V 4000 2900 50  0000 C CNN
F 2 "" V 3930 2900 50  0001 C CNN
F 3 "" H 4000 2900 50  0001 C CNN
	1    4000 2900
	1    0    0    -1  
$EndComp
$Comp
L CONN_01X02 J201
U 1 1 58D46616
P 3150 2900
F 0 "J201" H 3150 3050 50  0000 C CNN
F 1 "Sensor" V 3250 2900 50  0000 C CNN
F 2 "" H 3150 2900 50  0001 C CNN
F 3 "" H 3150 2900 50  0001 C CNN
	1    3150 2900
	-1   0    0    -1  
$EndComp
$Comp
L GNDA #PWR205
U 1 1 58D466F6
P 3850 3750
F 0 "#PWR205" H 3850 3500 50  0001 C CNN
F 1 "GNDA" H 3850 3600 50  0000 C CNN
F 2 "" H 3850 3750 50  0001 C CNN
F 3 "" H 3850 3750 50  0001 C CNN
	1    3850 3750
	1    0    0    -1  
$EndComp
Text GLabel 3850 2600 1    60   Input ~ 0
Vref
Text Label 3300 3200 0    60   ~ 0
A
Text Label 4150 3200 2    60   ~ 0
B
Text Label 4100 3100 0    60   ~ 0
A
$Comp
L GNDA #PWR204
U 1 1 58D46DAE
P 5500 3600
F 0 "#PWR204" H 5500 3350 50  0001 C CNN
F 1 "GNDA" H 5500 3450 50  0000 C CNN
F 2 "" H 5500 3600 50  0001 C CNN
F 3 "" H 5500 3600 50  0001 C CNN
	1    5500 3600
	1    0    0    -1  
$EndComp
Text GLabel 5850 3600 2    60   Input ~ 0
Vref/2
$Comp
L C C203
U 1 1 58D47450
P 4450 3100
F 0 "C203" V 4500 3150 50  0000 L CNN
F 1 "1µF" V 4300 3000 50  0000 L CNN
F 2 "" H 4488 2950 50  0001 C CNN
F 3 "" H 4450 3100 50  0001 C CNN
	1    4450 3100
	0    1    1    0   
$EndComp
$Comp
L C C204
U 1 1 58D47535
P 4450 3500
F 0 "C204" V 4400 3550 50  0000 L CNN
F 1 "1µF" V 4600 3400 50  0000 L CNN
F 2 "" H 4488 3350 50  0001 C CNN
F 3 "" H 4450 3500 50  0001 C CNN
	1    4450 3500
	0    1    1    0   
$EndComp
Text HLabel 7900 3400 2    60   Input ~ 0
OUTPUT0
Text Notes 4200 2700 0    60   ~ 0
Optional AC Coupling\n3dB down @ 0.4Hz
$Comp
L CONN_01X03 J202
U 1 1 58D482DB
P 7200 3000
F 0 "J202" H 7150 3200 50  0000 C CNN
F 1 "Bypass Antialias Filter" V 7300 3000 50  0000 C CNN
F 2 "" H 7200 3000 50  0001 C CNN
F 3 "" H 7200 3000 50  0001 C CNN
	1    7200 3000
	0    -1   -1   0   
$EndComp
$Comp
L AD8622 U101
U 1 1 58D497DC
P 5500 5050
F 0 "U101" H 5700 5200 50  0000 L CNN
F 1 "AD8622" H 5700 4900 50  0000 L CNN
F 2 "" H 5500 5050 50  0001 C CNN
F 3 "" H 5500 5050 50  0001 C CNN
	1    5500 5050
	1    0    0    -1  
$EndComp
$Comp
L C C206
U 1 1 58D49933
P 4800 5100
F 0 "C206" H 4825 5200 50  0000 L CNN
F 1 "910pF" H 4700 5000 50  0000 L CNN
F 2 "" H 4838 4950 50  0001 C CNN
F 3 "" H 4800 5100 50  0001 C CNN
	1    4800 5100
	1    0    0    -1  
$EndComp
$Comp
L C C205
U 1 1 58D499AB
P 5150 4500
F 0 "C205" V 5100 4550 50  0000 L CNN
F 1 "9.1nF" V 5200 4550 50  0000 L CNN
F 2 "" H 5188 4350 50  0001 C CNN
F 3 "" H 5150 4500 50  0001 C CNN
	1    5150 4500
	0    1    1    0   
$EndComp
$Comp
L R R209
U 1 1 58D49A2E
P 4550 4950
F 0 "R209" V 4630 4950 50  0000 C CNN
F 1 "1.15M" V 4550 4950 39  0000 C CNN
F 2 "" V 4480 4950 50  0001 C CNN
F 3 "" H 4550 4950 50  0001 C CNN
	1    4550 4950
	0    1    1    0   
$EndComp
$Comp
L R R208
U 1 1 58D49ACD
P 4150 4950
F 0 "R208" V 4230 4950 50  0000 C CNN
F 1 "86.6k" V 4150 4950 50  0000 C CNN
F 2 "" V 4080 4950 50  0001 C CNN
F 3 "" H 4150 4950 50  0001 C CNN
	1    4150 4950
	0    1    1    0   
$EndComp
$Comp
L GNDA #PWR207
U 1 1 58D49BFF
P 4800 5250
F 0 "#PWR207" H 4800 5000 50  0001 C CNN
F 1 "GNDA" H 4800 5100 50  0000 C CNN
F 2 "" H 4800 5250 50  0001 C CNN
F 3 "" H 4800 5250 50  0001 C CNN
	1    4800 5250
	1    0    0    -1  
$EndComp
Text Notes 600  1800 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: 0.1%\nR208, R209: 1%\nR202, R205, R206: Metal Foil / Thin Film (>1% if DC coupled)\nALL C: 5%, 16V
$Comp
L R R207
U 1 1 58D47410
P 4750 3500
F 0 "R207" V 4830 3500 50  0000 C CNN
F 1 "390k" V 4750 3500 50  0000 C CNN
F 2 "" V 4680 3500 50  0001 C CNN
F 3 "" H 4750 3500 50  0001 C CNN
	1    4750 3500
	1    0    0    -1  
$EndComp
$Comp
L R R203
U 1 1 58D47392
P 4750 3100
F 0 "R203" V 4830 3100 50  0000 C CNN
F 1 "390k" V 4750 3100 50  0000 C CNN
F 2 "" V 4680 3100 50  0001 C CNN
F 3 "" H 4750 3100 50  0001 C CNN
	1    4750 3100
	1    0    0    -1  
$EndComp
Text GLabel 4650 3300 0    60   Input ~ 0
Vref/2
$Comp
L GNDA #PWR202
U 1 1 58D5ED2F
P 2000 4150
F 0 "#PWR202" H 2000 3900 50  0001 C CNN
F 1 "GNDA" H 2000 4000 50  0000 C CNN
F 2 "" H 2000 4150 50  0001 C CNN
F 3 "" H 2000 4150 50  0001 C CNN
	1    2000 4150
	1    0    0    -1  
$EndComp
$Comp
L C C201
U 1 1 58D5F9F5
P 2000 4000
F 0 "C201" H 2025 4100 50  0000 L CNN
F 1 "0.1μF" H 2025 3900 50  0000 L CNN
F 2 "" H 2038 3850 50  0001 C CNN
F 3 "" H 2000 4000 50  0001 C CNN
	1    2000 4000
	1    0    0    -1  
$EndComp
Text Notes 3850 5800 0    60   ~ 0
Chebyshev (0.23dB)\n-3dB @ 195Hz\n-50dB @ 3.1kHz
$Comp
L VBATT #PWR206
U 1 1 58D55284
P 5450 4800
F 0 "#PWR206" H 5450 4650 50  0001 C CNN
F 1 "VBATT" H 5450 4950 50  0000 C CNN
F 2 "" H 5450 4800 50  0000 C CNN
F 3 "" H 5450 4800 50  0000 C CNN
	1    5450 4800
	1    0    0    -1  
$EndComp
$Comp
L GNDA #PWR208
U 1 1 58D552E6
P 5450 5300
F 0 "#PWR208" H 5450 5050 50  0001 C CNN
F 1 "GNDA" H 5450 5150 50  0000 C CNN
F 2 "" H 5450 5300 50  0001 C CNN
F 3 "" H 5450 5300 50  0001 C CNN
	1    5450 5300
	1    0    0    -1  
$EndComp
$Comp
L AD8227 U201
U 1 1 58D55D88
P 5500 3300
F 0 "U201" H 5650 3425 50  0000 L CNN
F 1 "AD8227" H 5650 3175 50  0000 L CNN
F 2 "" H 5600 3300 50  0001 C CNN
F 3 "" H 5600 3300 50  0001 C CNN
	1    5500 3300
	1    0    0    -1  
$EndComp
$Comp
L R_Small R204
U 1 1 58D5622C
P 5100 3300
F 0 "R204" V 5150 3200 50  0000 L CNN
F 1 "1.78k" V 5095 3235 31  0000 L CNN
F 2 "" H 5100 3300 50  0001 C CNN
F 3 "" H 5100 3300 50  0001 C CNN
	1    5100 3300
	1    0    0    -1  
$EndComp
Text Notes 5000 3150 0    39   ~ 0
G=50
$Comp
L VBATT #PWR203
U 1 1 58D567E9
P 5500 3000
F 0 "#PWR203" H 5500 2850 50  0001 C CNN
F 1 "VBATT" H 5500 3150 50  0000 C CNN
F 2 "" H 5500 3000 50  0000 C CNN
F 3 "" H 5500 3000 50  0000 C CNN
	1    5500 3000
	1    0    0    -1  
$EndComp
Wire Wire Line
	3450 2950 3450 3200
Wire Wire Line
	3450 2950 3350 2950
Connection ~ 3650 3200
Wire Wire Line
	3350 2850 3350 2750
Wire Wire Line
	3350 2750 4000 2750
Connection ~ 3650 2750
Wire Wire Line
	3850 2750 3850 2600
Connection ~ 3850 2750
Wire Wire Line
	3650 3650 4000 3650
Wire Wire Line
	3850 3650 3850 3750
Connection ~ 3850 3650
Connection ~ 3450 3200
Wire Wire Line
	3300 3200 3650 3200
Wire Wire Line
	3650 3050 3650 3350
Wire Wire Line
	4000 3050 4000 3350
Wire Wire Line
	4150 3200 4150 3500
Wire Wire Line
	4100 3100 4300 3100
Wire Notes Line
	4300 2800 4950 2800
Wire Wire Line
	5200 5150 5050 5150
Wire Wire Line
	5050 5150 5050 5550
Wire Wire Line
	6150 4500 6150 5550
Wire Wire Line
	5800 5050 7300 5050
Wire Wire Line
	4300 4950 4400 4950
Wire Wire Line
	4700 4950 5200 4950
Connection ~ 4800 4950
Wire Wire Line
	4350 4950 4350 4500
Wire Wire Line
	4350 4500 5000 4500
Connection ~ 4350 4950
Wire Wire Line
	6150 4500 5300 4500
Connection ~ 6150 5050
Wire Wire Line
	4000 4950 4000 4250
Wire Wire Line
	4000 4250 6750 4250
Wire Wire Line
	6750 4250 6750 3300
Wire Wire Line
	7200 3200 7200 3400
Wire Wire Line
	7100 3300 7100 3200
Connection ~ 6750 3300
Wire Wire Line
	7300 5050 7300 3200
Wire Notes Line
	3800 4350 6900 4350
Wire Notes Line
	6900 4350 6900 5800
Wire Notes Line
	3800 5800 3800 4350
Wire Wire Line
	6150 5550 5050 5550
Wire Wire Line
	4600 2950 5000 2950
Wire Wire Line
	4600 2950 4600 3100
Connection ~ 4750 2950
Wire Wire Line
	4600 3500 4600 3650
Wire Wire Line
	4750 3250 4750 3350
Wire Wire Line
	4650 3300 4750 3300
Connection ~ 4750 3300
Wire Wire Line
	4150 3500 4300 3500
Wire Wire Line
	4600 3650 5000 3650
Connection ~ 4750 3650
Wire Notes Line
	4300 3800 4950 3800
Wire Notes Line
	4950 3800 4950 2800
Wire Notes Line
	4300 2800 4300 3800
Connection ~ 2000 4150
Connection ~ 2000 3850
Wire Notes Line
	6900 5800 3800 5800
Wire Wire Line
	5850 3600 5600 3600
Wire Wire Line
	5000 2950 5200 3100
Wire Wire Line
	5000 3650 5200 3500
Wire Wire Line
	5900 3300 7100 3300
Wire Wire Line
	5200 3200 5100 3200
Wire Wire Line
	5200 3400 5100 3400
Connection ~ 4000 3200
Wire Wire Line
	4000 3200 4150 3200
Text Notes 4200 2750 0    39   ~ 0
When DC coupled, sensor failure grounds output.
Text Notes 5000 4050 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 5700 5750 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 6200 4450 0    60   ~ 0
Antialias Filter
$Comp
L C C202
U 1 1 58D586D6
P 2250 4000
F 0 "C202" H 2275 4100 50  0000 L CNN
F 1 "10μF" H 2275 3900 50  0000 L CNN
F 2 "" H 2288 3850 50  0001 C CNN
F 3 "" H 2250 4000 50  0001 C CNN
	1    2250 4000
	1    0    0    -1  
$EndComp
Wire Wire Line
	2250 4150 2000 4150
Wire Wire Line
	2250 3850 2000 3850
$Comp
L VBATT #PWR201
U 1 1 58D58832
P 2000 3850
F 0 "#PWR201" H 2000 3700 50  0001 C CNN
F 1 "VBATT" H 2000 4000 50  0000 C CNN
F 2 "" H 2000 3850 50  0000 C CNN
F 3 "" H 2000 3850 50  0000 C CNN
	1    2000 3850
	1    0    0    -1  
$EndComp
Wire Wire Line
	7200 3400 7900 3400
Text Notes 7200 5700 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 7200 6700 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 800  7700 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: Probably useless\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
$EndSCHEMATC