background image

Instrumentation amplifier configuration

UM1955

4/28

DocID028405 Rev 1

1 Instrumentation 

amplifier 

configuration

The instrumentation amplifier configuration allows you to amplify a differential signal without 
impacting it thanks to the high impedance of operational amplifier input stage. Moreover, 
with the high accuracy resistors, this configuration features high rejection to common mode 
voltage.

1.1 Schematic 

diagram

Figure 2

 below depicts the circuit schematic of the instrumentation amplifier configuration.

Figure 2. Instrumentation amplifier configuration circuit schematic

1.2 

How to set up the board

The instrumentation amplifier section of the expansion board includes several jumpers for 
improved versatility. For this configuration, jumpers JP2, JP4 and JP5 must be mounted and 
JP6 and JP7 should not be mounted. If the input signal is capacitive, a bias voltage needs to 
be added. This configuration is possible by mounting jumpers JP6 and JP7. Once jumpers 
have been set in the required configuration, the differential must be connected to pins Inst_n 
and Inst_p.

9

9

76=,37 $

N

5

N

5

*1'

9

0

5

S)

&

1& 5

9

1& 5

*1'

$

9UHI

*1'

76=,37 &

76=,37 %

*1'

9UHI

9UHI

0

5

S)

&

N

5

N

5

N

5

N

5

Q)

&

N

5

N

5

S)

&

-3

-3

9

-3

-3

-3

,QVWBQ

5JDLQBD

5JDLQBE

,QVWBS

73

N

5J

9EXV

*1'

,2

,2

,2

,2

(6'

(6'$/&/6&

73

*1'

*63*',

Summary of Contents for X-NUCLEO-IKA01A1

Page 1: ...ess mainly focus on the distribution of electronic components Line cards we deal with include Microchip ALPS ROHM Xilinx Pulse ON Everlight and Freescale Main products comprise IC Modules Potentiometer IC Socket Relay Connector Our parts cover such applications as commercial industrial and automotives areas We are looking forward to setting up business relationship with you and hope to provide you...

Page 2: ...LED or coils or in a comparator architecture Thanks to its current sensing configuration it allows current measurement of any device that has a USB port For this configuration and the instrumentation amplifier configuration a highly accurate operational amplifier TSZ124 is used The expansion board also contains Nanopower TSU104 and Micropower TSV734 operational amplifiers for mobile applications T...

Page 3: ...2 4 Software and measurements 8 3 Buffer configuration 9 3 1 How to set up the board 9 3 2 Theoretical output 9 4 Full wave rectifier 10 4 1 Schematic diagram 10 4 2 How to set up the board 10 4 3 Theoretical output 10 4 4 Measurement example 10 5 Photodiode UV sensor 11 5 1 Schematic diagram 11 5 2 How to set up the expansion board 11 5 3 Measurement example 11 5 4 Additional possible use 12 6 LE...

Page 4: ...tical output 16 8 Prototyping area 17 9 Scenario examples 18 9 1 Current sensing motor outside of standard operation 18 9 2 Strain gauge 18 9 3 Electromyogram 18 9 4 Body detection 19 10 Operational amplifiers on the expansion board 20 11 Schematic diagrams 21 12 Bill of material BOM 23 13 Revision history 27 ...

Page 5: ...rumentation amplifier configuration circuit schematic 1 2 How to set up the board The instrumentation amplifier section of the expansion board includes several jumpers for improved versatility For this configuration jumpers JP2 JP4 and JP5 must be mounted and JP6 and JP7 should not be mounted If the input signal is capacitive a bias voltage needs to be added This configuration is possible by mount...

Page 6: ...3 2 V The gain of this instrumentation amplifier structure is defined by Equation 2 Note that it is also possible to increase the gain of the configuration by adding an external resistor on the Rgain_a and Rgain_b pins When an external resistor is used to change the gain jumper JP2 must be unmounted With this circuitry the maximum frequency of the input signal is 850 Hz based on the op amp GBP and...

Page 7: ...de current sensing structure This means that the current is measured close to the supply voltage thus before the application Figure 3 illustrates this concept Figure 3 High side current sensing application principle 2 1 Schematic diagram Figure 4 shows the circuit schematic of the current sensing configuration Figure 4 Current sensing configuration circuit schematic N 5I 5J P 5V Q I 1 76 37 1 N 5I...

Page 8: ...y voltage should be connected to Iin and Iout should be connected to the power supply voltage pin of the application 2 3 Theoretical output The output voltage of the operational amplifier is proportional to the measured current as the following formula illustrates Equation 4 Therefore Equation 5 Similar to the instrumentation amplifier configuration the operational amplifier for this configuration...

Page 9: ...igher current is drawn through the application the operational amplifier will be saturated and thus its output voltage will not reflect the real current The following table shows the correspondence between measured current output voltage and LSB on ADC Table 1 Output parameter values for current sensing configuration Current A Output voltage of operational amplifier Voltage after divider bridge at...

Page 10: ...et up the board In order to use the buffer configuration on the expansion board users simply connect their signal to the in pin on the buffer section of the board The output signal can be retrieved on the out pin in the same board section The output voltage of the operational amplifier is not intended to be connected to any microcontroller input on the expansion board since this configuration is m...

Page 11: ...4 2 How to set up the board The input signal must be connected to the Rect_in pin within the rectifier expansion board section Similarly the output signal is available on the Rect_out pin The output voltage of the rectifier structure is not intended to be connected to any microcontroller input on the board since this configuration is most often connected to another analog block 4 3 Theoretical out...

Page 12: ...s voltage is available on pin A4 of the Arduino UNO R3 connector and PC1 of the ST morpho connectors not mounted in the expansion board 5 3 Measurement example Here three examples have been selected Case 1 The board is placed inside a closed box Vout 33 mV Vol of the operational amplifier which is saturating Case 2 The board is in ambient light Vout 420 mV Case 3 The sensor is below a light source...

Page 13: ...figuration it is also possible to connect a UV ultraviolet sensor in order to derive the UV index instead of ambient light A free footprint is available on the expansion board to enable this possibility Note that if using a UV sensor R26 should be aligned to the UV sensor datasheet recommendation and the photodiode must be removed For additional details on the analog conditioning circuit used for ...

Page 14: ...ge varies the current and thus the light intensity is highly variable Figure 7 Forward current vs forward voltage This is why it is recommended to control the LED by current and thus this architecture is useful 6 1 Schematic diagram Figure 8 shows the circuit schematic of the LED driver configuration Figure 8 LED driver configuration circuit schematic S 5 1 4 131 1 1 769 37 N 5 1 Q N 5 N 5 3 B B 9...

Page 15: ..._K on the expansion board Moreover if needed it is possible to disconnect the mounted LED by removing jumper JP1 Note also that the supply voltage of the LED can be either external or based on the internal 3 3 V If several LEDs are in parallel or a higher power is needed it is recommended to place the Vcc jumper in the Vext position and use an external power supply Depending the PWM duty cycle the...

Page 16: ...amplifier toggles 7 1 Schematic diagram Figure 9 shows the schematic of the window comparator configuration Figure 9 Window comparator configuration circuit schematic 7 2 How to set up the board To set up the expansion board connect the signal to the in pin within the window comparator section The high and low threshold voltages then need to be defined by tuning the P2 potentiometer Threshold volt...

Page 17: ...no UNO R3 connectors or PA10 and PB5 on the ST morpho connectors not mounted in the expansion board must be monitored 7 3 Theoretical output The operational amplifier output toggles when the signal is out of the specified window Vin Vthreshold_low D2 high state D4 low state Vthreshold_low Vin Vthreshold_high D2 high state D4 high state Vthreshold_high Vin D2 low state D4 high state Figure 10 depic...

Page 18: ...ion board components on input and output and a divider bridge for a 5 V to 3 3 V conversion as shown on the following figure Figure 11 Prototyping area Note also that the supply voltage of the operational amplifier can be either external or based on the internal 3 3 V If a high output voltage and thus a higher power supply voltage is required it is recommended to place jumper JP3 in the Vext posit...

Page 19: ... action in order to prevent damage to the application This scenario uses the following configuration available on the expansion board Current sensing or instrumentation amplifier structure Window comparator LED driver Note that with the instrumentation amplifier configuration an external shunt resistor is required But it will allow you to sense the current in both clockwise and counter clockwise d...

Page 20: ...ensor which indicates whether it is day or night This functionality allows lighting a room only at night Note that the LED driver configuration contains a slot for plugging in additional LEDs in parallel if for example you wish to provide light in several directions at the same time This scenario uses the following configuration available on the expansion board Instrumentation amplifier structure ...

Page 21: ...erational amplifiers in the same package Table 2 Operational amplifier main parameters Configuration on the expansion board Icc per amplifier µA GBP kHz Vio max µV Comments TSZ124 Instrumentation amplifier current sensing 31 400 5 5 V operational amplifier Very high accuracy Available in QFN package TSV734 Buffer rectifier LED driver 59 850 200 5 V operational amplifier High accuracy Available in ...

Page 22: ...37 N 5 9 9 2S PS 2S PS 1 9 1 1 1 3URWR W SLQJ DUHD 3U GULYHU 3KRWRGLRGH 89 VHQVRU 1 1 S N 5 1 9FF Q 1 1 9FF LQBLQ QG JDWH I RXWSXW ORZ RXW RI ZLQGRZ N 3 N 5 1 1 89 N 5 1 1 S N 5 N 5 N 5 9 9 768 37 768 37 Q N 5 N 5 Q N 5 3 3U 3U 3U B B 3U 2XW 2XW 2XW 2XW 1 1 1 1 N 5 1 1 1 1 9 9UHI QWHUQDO EXIIHU 768 37 N 5 S N 5 9FF 9H W 9DQD 9DQD 3 9DQD UGXLQR 812 5 RQQHFWRUV 1 0 5 1 9H W 3U 3U 3U Q Q Q Q 2XW 2XW ...

Page 23: ...SOLILHU XOO ZDYH 5HFWLILHU 1 5 9 1 5 1 9UHI N 3 9 1 1 Q I 1 1 XIIHU 1 1 1 76 37 76 37 76 37 769 37 769 37 9 9 769 37 9FF Q 1 1 1 9UHI 9UHI 0 5 S N 5 N 5I N 5 N 5 N 5 Q N 5 N 5 S 5J N 5 N 5 S Q I S N 5 N 5 N 5 N 5 N 5 N 5 N 5 S 3 3 3 3 3 QVWBQ 5JDLQBD 5JDLQBE QVWBS 73 LQ RXW 5HFW BRXW 5HFW BLQ XIIBRXW XIIBLQ N 5J XVE 1 1 9 9EXV 1 2 2 2 2 6 6 6 9FF 0 5 Q 9EXV 1 86 9EXV 1 0LFUR 86 73 9EXV 1 2 2 2 2 6...

Page 24: ... 11 1 D1 Photodiode Through hole 12 1 D2 LED Orange Red SMD0603 13 2 D3 D4 Diode BAT48JFILM SOD 323 14 1 Dusb USB protection ESDA7P60 1U1M 1610 15 2 ESD1 ESD2 ESD protection dual ESDALCL6 2SC6 SOT23 6L 16 1 ESD3 ESD protection ESDALC6V1 1M2 SOD882 17 1 J1 USB A connector 18 1 J2 micro USB B connector 19 6 JP1 JP2 JP4 JP5 JP6 JP7 TSH 2 54 mm TSH 2 54 20 1 JP3 TSH 2 54 mm TSH 2 54 21 5 JP1 JP2 JP3 J...

Page 25: ...5 R23 R30 R33 R35 R37 Resistor 20 k SMD0603 37 1 R24 Resistor 62 k SMD0603 38 1 R26 Resistor 470 k SMD0603 39 4 R34 R36 R38 R39 Resistor 39 k SMD0603 40 2 Rf1 Rf2 Resistor 12 k SMD0603 41 2 Rg1 Rg2 Resistor 100 SMD0603 42 1 Rs Resistor 20 M SMD0805 43 1 TSU104IPT Operational amplifier TSU104IPT TSSOP14 44 1 TSV734IPT Operational amplifier TSV734IPT TSSOP14 45 1 TSZ124IPT Operational amplifier TSZ1...

Page 26: ... Additional notes 1 2 3 4 5 6 Not mounted 7 Not mounted 8 Not mounted 9 10 11 Vishay TEFD4300F 12 13 ST BAT48JFILM 14 ST ESDA7P60 1U1M 15 ST ESDALCL6 2SC6 16 ST ESDALC6V1 1M2 17 18 19 20 21 JP3 jumper must be set on Internal 3 3V position 22 23 24 CAN BE REMOVED NOT MOUNTED 25 CAN BE REMOVED NOT MOUNTED 26 27 ST 28 29 30 31 32 ...

Reviews: