ST STEVAL-AKI001V1 User manual

Introduction
The STEVAL-AKI001V1 evaluation board allows the user to evaluate the conversion performance of the ADC120 8-channel
analog-to-digital converter designed for 50 ksps to 1 Msps conversion.
The board has several on-board sources like temperature sensor and strain gauge signals, and can accept external signals to
allow measurement and evaluation of the ADC120 conversion performance based on its successive approximation register
(SAR) with internal track-and-hold cell.
The board is supplied ready-to-use in standalone mode, or it can be plugged onto a NUCLEO-L476RG board with SMT32
microcontroller, which enables further signal processing and PC communication.
Figure 1. STEVAL-AKI001V1 evaluation board for the ADC120
How to use the evaluation board for the ADC120 8-channel analog to digital
converter
UM2691
User manual
UM2691 - Rev 2 - September 2020
For further information contact your local STMicroelectronics sales office.
www.st.com

1Board overview
The board inputs are configured on the following J2 connector pins:
•Pin 8 (In3): input for ±5V signal
• PIN 10 (In4): input configurable to measure around 1.7 V reference voltage or external 0 to 3V3 voltage
(selected using jumper J31)
• Pin 12 (In5): input for 0 to 3V3 signal (no filtering)
• Pin 14 (In6): input not directly connected, footprints are left to the user to allow amplification
• Pin 16 (In7): input not directly connected, footprints are left to the user to allow amplification
Figure 2. STEVAL-AKI001V1 block diagram
The STEVAL-AKI001V1 evaluation board includes the following hardware functionality:
•2.54mm, 38cts double female connectors to be plugged to the STM32L476RG Nucleo development board
(J1)
• 2.54mm, 10cts, double male connector to connect an SPI to UART communication module (J3)
• Several configuration jumpers to select power supply input
• 3V3 LDO for power supply (JP4 5V jumper and JP5 LDO 3V3)
• A TS3431 voltage reference
• An analog to digital converter ADC120 SAR, 12 bits, 8 inputs (IN0 to IN7)
• An STLM20 temperature sensor on IN0
• A PT100 resistance thermometer on IN1
• Acquisition of a ±5V signal on IN3
• Voltage reference sampling necessary for precise calculations
• Sampling of a 0 to 3V3 voltage input
• Acquisition of amplified inputs (not connected) configurable by the user on 2 channels (IN6 and IN7)
• Instrumentation amplifier for a strain gauge on IN2
The SPI communication lines are connected to the SPI communication lines of the STM32L476RG Nucleo
development board and to the connector dedicated to the SPI to UART communication module. The jumpers are
configured in the following way:
• JP4 - 5VNUC
• JP5 - AVCC
UM2691
Board overview
UM2691 - Rev 2 page 2/27

• J31 - VREF
•J44 - GND
UM2691
Board overview
UM2691 - Rev 2 page 3/27

2Board connection and operation
2.1 Power supply
The power supply input can be selected form the following sources:
•5V from Nucleo board or external supply (if Nucleo is not used)
• 3V3 voltage from Nucleo development board.
JP4 enables the 3V3 LDO that converts the 5V into 3V3.
JP5 chooses between 3V3 vai the LDO and 3V3 from the Nucleo
Figure 3. Power supply selection jumpers
C16
1µF
GND
GND
C14
1µF
C17
1µF
C18
0.1µF
GND
3.3V_NUCLEO
DVCC
3.3V_D Generate
JP4
DVCC Generate
JP5
GND
GND
IN
1
EN
3
GND
2
4
5
IC11
LDK220M
5V_NUCLEO
AVCC
ADJ/NC
OUT
2.2 SPI communication
The ADC120 has the following SPI communication inputs and oututs
•DIN line is MOSI (Master Output Slave Input)
• DOUT line is MISO (Master Input Slave Output)
• SCLK line is the clock
• CS line is Chip Select
UM2691
Board connection and operation
UM2691 - Rev 2 page 4/27

Figure 4. ADC120 SPI timing diagram
2.3 Board operation
The ADC120 channel to be read can be selected by sending the proper code through the DIN (MOSI) line.
The reading on DOUT provides the converted raw data. A code running inside a microcontroller can calculate the
proper value in volts or in degrees Celsius, depending on the analog sensor used.
RELATED LINKS
Visit the ST website to download application note AN5454
UM2691
Board operation
UM2691 - Rev 2 page 5/27

3STEVAL-AKI001V1 ADC inputs
3.1 ADC channel 0: temperature measurement
The input channel 0 on the ADC120 receives the converted output from the STLM20 analog temperature sensor
on the evaluation board.
Figure 5. STEVAL-AKI001V1 schematic - temperature measurement with STLM20
NC
1
GND
2
VOUT 3
VCC 4
GND
5
IC51
STLM20
R60
470
AVCC
ADC_0
SBR0220T5-7
D51
NC
C55
0.1µF
GND
GND
C53 0.1µF
GND
AVCC
AVCC
The voltage V (V) image of the temperature T (°C) is given by the following equation:
VADC0=−3.88*106*T2+−1.15*10−2*T+ 1.8639 (1)
RELATED LINKS
Visit the STLM20 product page on the ST website for more information regarding this device
3.2 ADC channel 1: temperature measurement
The input channel 1 on the ADC120 receives the voltage image of the PT100 resistor on the evaluation board.
Figure 6. STEVAL-AKI001V1 schematic - temperature measurement with PT100
Rref
698
PT100
100 C57
10nF
ADC_1
R64
330
C59
10nF
SBR0220T5-7
D52
NC
AVCC
GND
GND
AVCC
C54 22nF
GND
V_REF
R55
3.6K
R56
3.6K
R57
1.8K
GND
R58
1.8K
GND
R59
1.8K
V+
V-
+
3-
2
1
4 8
IC52A
TSU112
+5
-6
7
IC52B
TSU112
GND
4
5
+
1
-
3
2
V+
V- IC53
TSU111
R62
2K
R63
20K
GND
AVCC
C58 10nF
GND
GND
C52
10µF
C51
0.1µF
The resistance R100 image of the temperature is given by the following equation:
UM2691
STEVAL-AKI001V1 ADC inputs
UM2691 - Rev 2 page 6/27

RPT100 =VADC1*2*Rref
11*Vref (2)
And the temperature T is given by:
T=
RPT100
R0−1
α(3)
Where:
•R0=100Ω is the resistance at 0 °C
•α=0.00385
Ω
Ω
°C is the temperature coefficient
3.3 ADC channel 2: input for strain gauge measurement
The ADC120 input channel 2 measures and amplifies the strain gauge variation via a Wheatstone bridge.
Figure 7. STEVAL-AKI001V1 schematic - instrumentation amplifier for strain gauge measurement
R43
120
R44
120
R45
120
R46
EXTERNAL RESITOR
AVCC
ADC_2
0.1%
R48
1K
Strain gauge - R=120 ohms
GND
GND
FSG +
J41
FSG -
J42
Strain_gauge_ref
Strain Gauge Set
J44
AVCC
V-_Wheatstone
V+_Wheatstone
C4122nF
GND
0.1%
R47
20K
0.1%
R49
20K
0.1%
R50
33K
0.1%
R51
33K
C4322nF
GND
AVCC
GND
0.1%
R52
33K
0.1%
R53
33K
1
5
+
3
-
4
2
V+
V- IC42
TSZ121
R54
330
C44
10nF
SBR0220T5-7
D41
NC
AVCC
GND
V+
V-
+
3
-
2
1
4 8
IC41A
TSZ122
+
5-
6
7
IC41B
TSZ122
J43
GND
AVCC
The ADC120 reads the voltage image of the amplified voltage variation.
If jumper J44 is connected to GND, the voltage image of the strain gauge voltage variation is given by the
following equation:
VADC2=VWℎeatsone
−− VWℎeatsone
+1 + 2*R47
R48
R53
R51 (4)
If jumper J44 is not connected to GND, an offset given by channel input 6 is implemented.
3.4 ADC channel 3: acquisition of a ±5 V signal on IN3
The ADC120 input channel 3 measures and converts a ±5V signal into a 0 to 3V3 signal through the rectifier
shown in the figure below.
UM2691
ADC channel 2: input for strain gauge measurement
UM2691 - Rev 2 page 7/27

Figure 8. STEVAL-AKI001V1 schematic - ±5 V to 0-3V3 voltage rectifier
1
5
+
3
-
4
2
V+
V- IC22
TSX711
R22
1K
R25
5K
R27
330
C24
10nF
SBR0220T5-7-F
D21
NC
ADC_3
R23
22KIN3
GND
GND
C22 22nF
AVCC
GND
V_REF
The ADC120 reads the positive voltage between 0 and 3V3. The rectified voltage is obtained from the equation:
VADC3=Vref − In3*0.1852
0.8149 (5)
3.5 ADC channel 4: reference voltage measurement
The ADC120 input channel 4 is used to measure the voltage of the inboard reference voltage provided by the
TS3431.
Figure 9. STEVAL-AKI001V1 schematic - reference voltage measurement
R40
330
C36
10nF
SBR0220T5-7
D32
NC
ADC_4 Generate
J31
V_REF
IN4
ADC_4
GND
AVCC
AVCC
ADC input 4 can be connected to the reference voltage or to another voltage on pin 10 of connector J2 by setting
jumper J31 on the left (VREF) or on the right (In4), respectively.
RELATED LINKS
Visit the TS3431 product page on the ST website for more information regarding this device
3.6 ADC channel 5: external 0-3V3 voltage measurement
Pin 12 on connector J2 can be used to connect a 0 to 3V3 voltage to test the conversion of the ADC120 on a
custom level voltage. The ADC120 input channel 5 is designed to be operated by the user with any 0 to 3V3
voltage.
Figure 10. STEVAL-AKI001V1 schematic - ADC input 5
R39
330
C35
10nF
SBR0220T5-7
D31
NC
ADC_5
GND
IN5
AVCC
UM2691
ADC channel 4: reference voltage measurement
UM2691 - Rev 2 page 8/27

3.7 ADC channel 6: user configurable gain input
Pin 14 of connector J2 can be used to connect a voltage and configure the schematic as shown below to provide
amplification, a divider, a filter, etc.
Figure 11. STEVAL-AKI001V1 schematic - user configurable gain ADC channel 6
GND
1
5
+
3
-
4
2
V+
V-
IC31
TSX711
R37
0
R41
330
C37
10nF
SBR0220T5-7
D33
NC
IN6
ADC_6
GND
R31 NC
R33
NC
GND
GND
R35
NC
C31 NC
Strain_gauge_ref
AVCC
C32 22nF
GND
AVCC
The ADC120 input channel 6 is designed for user configuration with any input voltage that does not surpass the
3V3 maximum input rating of the ADC120.
This channel 6 input voltage can also be used to provide the offset for the instrumentation amplifier on ADC
channel 2 by setting the jumper J44 on strain gauge ref.
3.8 ADC channel 7: user configurable gain input
Pin 16 of connector J2 can be used to connect a voltage and configure the schematic as shown below to provide
amplification, a divider, a filter, etc.
Figure 12. STEVAL-AKI001V1 schematic - user configurable gain ADC channel 7
1
5
+
3
-
4
2
V+
V-
IC32
TSX711
R38
0
R42
330
C38
10nF
SBR0220T5-7
D34
NC
IN7
ADC_7
GND
R32 NC
R34
NC
GND
GND
R36
NC
C33 NC
AVCC
C34 22nF
GND
AVCC
The ADC120 input channel 7 is designed for user configuration with any input voltage that does not surpass the
3V3 maximum input rating of the ADC120.
UM2691
ADC channel 6: user configurable gain input
UM2691 - Rev 2 page 9/27

4Schematic diagrams
Figure 13. STEVAL-AKI001V1 schematic diagram - functional blocks
J3
4
9
7
38
1
U_Plus_minus_5V_input to ADC
36
GND
14
V
11
IN0
13
A
10nF
10nF
GND
E5V
IN4
ADC_3
1
9
J4
ADC_1
N
10
DVCC
32
2
DIN
SPI interface (compatible with Aardvark connetor)
C
GND
16
ADC_5
D
14
29
IN5
U_Strain_gauge to ADC
31
26
5
V_REF
24
3 4
34
SPI_MOSI
DVCC
31
IN5
15
20
5V_NUCLEO
DOUT
SPI_MOSI
SPI_SS
C
22
7
SPI interface
5
ADC_0
30
3
IN6
30
GND
28
IN1
26
GND
7
35
SCLK
22
SPI_MISO
2
28
ADC120
1
C2
3
C
11
9J2
GND
Input Signal
NUCLEO - CN10
27
ADC_6
GND
3.3V_NUCLEO
G C
V_REF
16
GND
SPI_SCLK
25
GND
IN6
27
U_Standard ADC inputs
13
5
18
15
37
23 24
25
18
20
AVCC
33
D
5V_NUCLEO
35
IN3
A
6
23
Strain_gauge_ref
6
21
ADC_7
U_Power_Supply
VD
IN7
1
C3
17
/CS
29
U_Temperature sensors for ADC
AVCC
38
J1B
Left morpho connector
11
AVCC
16
IN7
12
33
32
4
19
2
NUCLEO - CN10
2
SPI_SCLK
12
19
ADC_4
IN2
N
Right morpho connector
ADC_2
IN3
34
14
Strain_gauge_ref
1
10
17
5V_NUCLEO
37
8
8
SPI_MISO
IN4
15
3
AVCC
J1A
GND
D
GND
10
G
V_REF
SPI_SS
36
AVCC
IC1
AVCC
21
Figure 14. STEVAL-AKI001V1 schematic diagram - power supply 3V3
C16
1µF
GND
GND
C14
1µF
C17
1µF
C18
0.1µF
GND
3.3V_NUCLEO
DVCC
3.3V_D Generate
JP4
DVCC Generate
JP5
GND
GND
IN
1
EN
3
GND
2
4
5
IC11
LDK220M
5V_NUCLEO
AVCC
ADJ/NC
OUT
UM2691 - Rev 2 page 10/27
UM2691
Schematic diagrams