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ADVANCED COMMUNICATIONS & SENSING

USER GUIDE

SX8724SEVK

Evaluation Kit for SX8724S Data Acquisition System

ACS - Revision 1.0 May 2011
© Semtech Corp.

17.9

LSB Equivalence

Using the defined ADC and PGA set-up, an equivalent input pressure per LSB can be calculated. Using the
typical sensor transfer function, we obtain:

The approximate equivalence between Pressure and altitude is defined as follow:

This implementation has a resolution of 8cm altitude.

Equation 4

Equation 5

Pressure

LSB

pressureRange

⋅

sensorVoltageRange

--------------------------------------------------------

63nV 200kPa

⋅

13.04mV

-------------------------------------

0.96Pa

Altitude

100kPa

8620m

≡

0.96Pa 8620m

⋅

100kPa

---------------------------------------

→

0.0079Pa

Содержание SX8724SEVK

Страница 1: ...Supply from 5V USB externally or regulated 3 3V USB interface with gateway to the SX8724S On board master MCU with flash memory access to all IO Prototyping area I Os board supplies and grounds place...

Страница 2: ...14 9 1 Gateway to SX8724S 14 10 EVK Bill of Materials List 16 11 Board Physical Dimensions 18 GRAPHICAL USER INTERFACE 19 12 Software Tool Overview 19 13 Main Window 20 13 1 Menu Tool Bar 20 13 2 Wind...

Страница 3: ...NTENT ADVANCED COMMUNICATIONS SENSING USER GUIDE SX8724SEVK Evaluation Kit for SX8724S Data Acquisition System 17 5 Reference Voltage Selection 40 17 6 ZoomingADC Configuration 42 17 7 ADC Configurati...

Страница 4: ...s of miniature sensors with a general purpose microcontroller The SX8724SEVK is a USB based evaluation tool designed to allow simple and easy evaluation of the suitability of the SX8724S device for a...

Страница 5: ...n System ACS Revision 1 0 May 2011 Semtech Corp 3 Board Overview The picture below describes the main zones and functions accessible on the SX8724SEVK Figure 1 SX8724SEVK Board Overview USB Gateway In...

Страница 6: ...the evaluation kit is supplied with an insert sheet follow the instruction on the insert sheet The latest software revision can be downloaded on Semtech website 1 Put the CDROM in your computer and b...

Страница 7: ...ur computer Administrator rights may be needed 4 The GUI software and Net Framework are now installed on your computer 4 1 About Microsoft NET Framework The Microsoft NET Framework 3 5 is required to...

Страница 8: ...ripheral Choose the Install the software automatically Recommended option and click on the Next button 2 Windows will search for the associated driver and install the board as new peripheral 3 Follow...

Страница 9: ...SCL 11 RB5 AN11 I OCB5 RX DT 12 RB4 AN10 I OCB4 SDI SDA 13 RC2 AN6 P 1D C12IN2 CVref I NT2 14 RC1 AN5 C12I N1 INT1 Vref 15 RC0 AN4 C12I N INT0 Vref 16 VUSB 17 RA1 I OCA1 D PGC 18 RA0 I OCA0 D PGD 19 V...

Страница 10: ...nts are available for industrial PCB terminal blocks and on the bare PCB next to the SX8724S Figure 4 Analog Interface Schematic Figure 5 SX8724S Interface on the Board MOSI SCLK SS READY 1 2 3 4 5 6...

Страница 11: ...E SX8724SEVK Evaluation Kit for SX8724S Data Acquisition System ACS Revision 1 0 May 2011 Semtech Corp 7 1 Prototyping Area Using the prototyping area one can set its own application only using the SX...

Страница 12: ...er Sources Specifications The board can be powered through three different sources 1 VBUS USB power coming from the PC 2 VLDO 3 3V Regulated voltage 3 VEXT External source applied on VEXT interface In...

Страница 13: ...tor User should place the jumper on the desired SX8724S supply voltage value Figure 7 Power Supply Schematic Figure 8 SX8724SEVK Power Supply Selector 1 2 J8 GND Ferrite F2 VBUS 1 D 2 D 3 GND 5 SHL D...

Страница 14: ...VBOARD VUSB RB6 RB4 RC7 OSC2 OSC1 RC5 RC4 RC3 RC2 RC1 RC0 RB5 RB7 PGD D PGC D MCLR VPP RC6 VDD 1 RA5 I OCA5 OSC1 CL K IN 2 RA4 AN3 I OCA3 OSC2 CL K OUT 3 RA3 I OCA3 MCL R VP P 4 RC5 CCP 1 P1A T0CK I 5...

Страница 15: ...Prototyping Area By default the jumper is not connected To enter in bootloader mode shortcut the BOOT LOADER J9 jumper and restart the PIC by unplug plug the SUPPLY jumper or disconnect connect the US...

Страница 16: ...al Connector mini USB2 0 Interconnects UX60 MB 5ST J7 Through Hole Right Angle Header BRKWAY 100 6POS R A Tyco Electronics 9 103325 0 06 Crystal Y1 Surface Mount HC49 US Crystal 12 00000 MHZ 18pF SMD...

Страница 17: ...Evaluation Kit for SX8724S Data Acquisition System ACS Revision 1 0 May 2011 Semtech Corp C4 C7 1uF SMD 0603 C5 C8 C12 C13 100nF SMD 0603 C9 C10 22pF SMD 0603 C11 47nF SMD 0603 C14 22nF SMD 0603 Tabl...

Страница 18: ...age 18 ADVANCED COMMUNICATIONS SENSING USER GUIDE SX8724SEVK Evaluation Kit for SX8724S Data Acquisition System ACS Revision 1 0 May 2011 Semtech Corp 11 Board Physical Dimensions Figure 12 SX8724SEVK...

Страница 19: ...which values must be written for board operation In addition the GUI simplifies analog interfacing by providing controls that simplify alignment of analog functions The figure below illustrates the SX...

Страница 20: ...through the short cut buttons of the Window Toolbar Save Config allows for SX8724xEVK configuration files cfg to be saved This is implemented through a standard Windows file dialog box The default fi...

Страница 21: ...iled in the SX8724S datasheet Refer to 15 Registers Display Window section for further information 13 1 3 Help Menu Help opens a HTML help window with GUI controls descriptions User s Guide opens a PD...

Страница 22: ...e drop down menus Open Config USB Connect Disconnect and Save Config buttons provides a direct control of the actions described in 13 1 1 File Menu section A configuration file illustrated below in Fi...

Страница 23: ...ystem ACS Revision 1 0 May 2011 Semtech Corp 13 3 Status Bar The Status Bar provides error messages the onboard SX8724S version and the current user configuration file For further information concerni...

Страница 24: ...quisition chain This can be the internally generated VREF with a nominal value of 1 22V or VBATT 2 4V to 5 5V When the control selects VREF it can also be selected combined with a GPIO to provide a re...

Страница 25: ...solution then NELCONV If the offset is important select a number of elementary conversions 1 The user has also the possibility to decide if the ADC will work in single shot or in continuous mode of sa...

Страница 26: ...bandgap related internal offset voltage and 1 f noise The bandgap chop state may be forced High or Low or may be set to toggle during conversion at either the same rate or half the rate of the Element...

Страница 27: ...the real device voltage value 13 6 Estimated Device Performances These data are theoretical values extracted from registers settings and computed according to the equations available in the datasheet...

Страница 28: ...3 offset controls Additionally this total offset is function of the contribution of PGA3 gain Therefore the total offset is computed as Output noise the output noise is computed using the input noise...

Страница 29: ...conversions The conversion time for an elementary conversion Sample rate the ADC output sample rate is computed with the TCONV time 13 7 Display Chart The display chart is a graphic representing the...

Страница 30: ...to File Set the Log selector to ON to access the Log control Max sample input box indicates how many ZoomingADC samples are stored in the log file Browse button let the user choose where to store the...

Страница 31: ...Note that the following panel options are available in the small display chart described in 13 7 Display Chart 14 1 1 Zoom left click on the panel If the user draws a rectangle in the graphic and the...

Страница 32: ...f 1000 consecutive samples Therefore the refresh rate is dependant of the sample rate If the signal is DC the distribution width shows the noise The samples are coded on 16 bits if the digital resolut...

Страница 33: ...ENOB that is measured using FFT and SINAD Its equation is as follows NFR the Noise Free Code Resolution or flicker free resolution is the number of bits of resolution beyond which it is impossible to...

Страница 34: ...ister are changed in the main GUI window the corresponding register displays the new contents of the register s highlighting changed contents in red for a period of approximately 5 seconds before reve...

Страница 35: ...nsor using the SX8724SEVK evaluation board It also shows how to use efficiently the ZoomingADC of the SX8724S and demonstrate the benefits of the zooming feature 17 2 Pressure Sensor The chosen sensor...

Страница 36: ...yp and max as a function of the absolute input pressure for the specified supply voltage Note The given transfer function in the datasheet is for a 10V power supply here the transfer function was tran...

Страница 37: ...differential input The default VMUX setting will select VBATT VSS as reference inputs for the acquisition chain The sensor will be biased with VBATT when D0 is set as digital output high state It wil...

Страница 38: ...Acquisition System ACS Revision 1 0 May 2011 Semtech Corp 17 2 4 Sensor Connection to the Board The picture below shows how to connect the sensor on the evaluation board each red point represents a co...

Страница 39: ...USB connector to the evaluation board and to the PC to power the board 4 Launch the Graphical User Interface 5 Start the connection to the EVK in the GUI 17 3 2 Voltages Settings In the Voltages grou...

Страница 40: ...ult button to start a default continuous acquisition mode to enable the acquisition chain 17 5 Reference Voltage Selection After having pressed the Set Default button as described in 17 4 Reading the...

Страница 41: ...t and Vout on a board the SX8724S allows inverting the polarity of the inputs we will use the sign inversion feature during SX8724S configuration 17 5 2 Rough Gain Configuration As the transfer functi...

Страница 42: ...zone of interest called measuring window in red below 17 6 2 Gain Computing To compute the total gain that must be applied to the sensor output signal we must know 2 parameters 1 The maximum output sp...

Страница 43: ...t removing PGA after PGAs PGA1 Amplified sensor output 6 5mV x 10 65mV PGA2 Amplified sensor output 65mV x 10 650mV Offset cancellation min 0 2 x VREF 3 3V x 0 2 660mV The minimum value is too big we...

Страница 44: ...NICATIONS SENSING USER GUIDE SX8724SEVK Evaluation Kit for SX8724S Data Acquisition System ACS Revision 1 0 May 2011 Semtech Corp The PGA group of controls should then look like as picture beside Figu...

Страница 45: ...to 8 5mV This window is represented in Figure 38 Figure 40 PGA Parameters ADC input sensor voltage vs pressure 0 200 400 600 800 1000 1200 1400 1600 1800 Pressure kPa Voltage mVDC Min Typ Max 2 0 2 4...

Страница 46: ...ing frequency 250 kHz Gain of PGA1 10 V V Gain of PGA2 10 V V Gain of PGA3 8 25 V V Total PGA gain 825 V V Offset of PGA2 0 00 VREF Offset of PGA3 1 58 VREF Total equivalent input offset 6 33 mV Over...

Страница 47: ...valuation Kit for SX8724S Data Acquisition System ACS Revision 1 0 May 2011 Semtech Corp 17 8 Noise Cancellation The OSR and NELCONV parameters can be increased in order to reduce the noise generated...

Страница 48: ...ADC and PGA set up an equivalent input pressure per LSB can be calculated Using the typical sensor transfer function we obtain The approximate equivalence between Pressure and altitude is defined as...

Страница 49: ...e range 2 Set the configuration to Gain 225 no offset cancellation as in 17 5 2 Rough Gain Configuration section 3 Then blow in the sensor tube try to make the maximum signal span The signal span corr...

Страница 50: ...cense under patent or other industrial or intellectual property rights Semtech assumes no responsibility or liability whatsoever for any failure or unexpected operation resulting from misuse neglect i...

Страница 51: ...Mouser Electronics Authorized Distributor Click to View Pricing Inventory Delivery Lifecycle Information Semtech SX8724SEVK...

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