ST STEVAL-AKI001V1 Manual de usuario

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

C14

1µF

C17

1µF

C18

0.1µF

GND

3.3V_NUCLEO

DVCC

3.3V_D Generate

JP4

DVCC Generate

JP5

GND

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 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

AVCC

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-

4 8

IC52A

TSU112

-6

IC52B

TSU112

GND

V+

V- IC53

TSU111

R62

R63

20K

GND

AVCC

C58 10nF

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:

RPT100

R0−1

α(3)

Where:

•R0=100Ω is the resistance at 0 °C

•α=0.00385

°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

Strain gauge - R=120 ohms

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

V+

V- IC42

TSZ121

R54

330

C44

10nF

SBR0220T5-7

D41

AVCC

GND

V+

V-

4 8

IC41A

TSZ122

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

V+

V- IC22

TSX711

R22

R25

R27

330

C24

10nF

SBR0220T5-7-F

D21

ADC_3

R23

22KIN3

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

ADC_4 Generate

J31

V_REF

IN4

ADC_4

GND

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

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

V+

V-

IC31

TSX711

R37

R41

330

C37

10nF

SBR0220T5-7

D33

IN6

ADC_6

GND

R31 NC

R33

GND

R35

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

V+

V-

IC32

TSX711

R38

R42

330

C38

10nF

SBR0220T5-7

D34

IN7

ADC_7

GND

R32 NC

R34

GND

R36

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

U_Plus_minus_5V_input to ADC

GND

IN0

10nF

GND

E5V

IN4

ADC_3

ADC_1

DVCC

DIN

SPI interface (compatible with Aardvark connetor)

GND

ADC_5

IN5

U_Strain_gauge to ADC

V_REF

3 4

SPI_MOSI

DVCC

IN5

5V_NUCLEO

DOUT

SPI_MOSI

SPI_SS

SPI interface

ADC_0

IN6

GND

IN1

GND

SCLK

SPI_MISO

ADC120

9J2

GND

Input Signal

NUCLEO - CN10

ADC_6

GND

3.3V_NUCLEO

G C

V_REF

GND

SPI_SCLK

GND

IN6

U_Standard ADC inputs

23 24

AVCC

5V_NUCLEO

IN3

Strain_gauge_ref

ADC_7

U_Power_Supply

IN7

/CS

U_Temperature sensors for ADC

AVCC

J1B

Left morpho connector

AVCC

IN7

NUCLEO - CN10

SPI_SCLK

ADC_4

IN2

Right morpho connector

ADC_2

IN3

Strain_gauge_ref

5V_NUCLEO

SPI_MISO

IN4

AVCC

J1A

GND

V_REF

SPI_SS

AVCC

IC1

AVCC

Figure 14. STEVAL-AKI001V1 schematic diagram - power supply 3V3

C16

1µF

GND

C14

1µF

C17

1µF

C18

0.1µF

GND

3.3V_NUCLEO

DVCC

3.3V_D Generate

JP4

DVCC Generate

JP5

GND

IC11

LDK220M

5V_NUCLEO

AVCC

ADJ/NC

OUT

UM2691 - Rev 2 page 10/27

UM2691

Schematic diagrams

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