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EVAL-AD5934EB 

Preliminary Technical Data

 

Rev. PrC | Page 6 of 32 

05

44

9-

0

02

NC

NC

NC

RFB

VIN

VOUT

NC

MCLK

SCL

SDA

AGND2

AGND1

DGND

AVDD2

AVDD1

DVDD

U6

AD5934

1

2

3

4

5

6

7

8

16

15

14

13

12

11

10

9

T1

T2

T5

T6

LK7

6

7

4

2

3

+VIN

TRIM

VOUT

GND

U4

ADR423

C32

0.1µF

C31

10µF

2

5

6

4

CLK2

LK6

LK2

LK3

LK12

LK10

LK5

C25
10µF

C26

0.1µF

C30
10µF

C28

0.1µF

C2
10µF

C24

0.1µF

C29

10µF

C27

0.1µF

LK8

LK9

C42

15pF

V

OUT

V

IN

VDD_AMP

R4

R3

R1
50

Ω

DGND

CLK1

DGND

VDD O/P

GND

XTAL1

C1

0.1nF

4

3

2

DVDD_5V

AVDD_SIG

AVDD_REF

DGND

DVDD_5V

LK1

DGND

DGND

T7

T8

SCL

SDA

VDD_REF

AGND DGND

AD820

U1

OUT

LK4

R2

LK11

5VUSB

NC = NO CONNECT

+

–

TEST

IMPEDANCE

FEEDBACK

RESISTOR

C41

 

Figure 2. Setup Link Position Circuit (A 15 pF Capacitor Connected Between VIN and VOUT, with RFB = 200 kΩ and a Precision 16 MHz Crystal Connected to MCLK) 

Содержание EVAL-AD5934EB

Страница 1: ...AD5934 and the application software developed to interface to the device The AD5934 is a high precision impedance converter system that combines an on board frequency generator with a 12 bit 250 kSPS ADC The frequency generator allows an external complex im pedance to be excited with a known frequency The response signal from the impedance is sampled by the on board ADC and the DFT is processed by...

Страница 2: ...on Descriptions 7 Getting Started 8 Setup Sequence Summary 8 Step 1 Install the Software 8 Step 2 Connect the USB Cable 9 Step 3 Verify the Links and Power Up the Evaluation Board 10 Step 4 Perform a Frequency Sweep 10 Frequently Asked Questions About Installation 13 Source Code for Impedance Sweeps 15 Evaluation Board Source Code Extract 16 Gain Factor Calculation 20 Impedance Measurement Tips 20...

Страница 3: ...ound plane at a single point underneath the board LINK FUNCTIONS Table 2 Link Function Descriptions Link No Function LK1 Link 1 is used to connect the output of the optional user supplied external operational amplifier U1 to the VOUT SMB connector see Figure 1 This op amp can be used to amplify buffer the output excitation voltage from the AD5934 Link 1 is used in conjunction with Link 6 and Link ...

Страница 4: ...ting amplifier user supplied which is accomplished by removing Link 6 and inserting Link 1 and Link 2 When link 6 is inserted the output of AD5934 is connected directly to the VOUT SMB connector When this link is inserted Link 1 and Link 2 must be removed When Link 6 is removed the output of the AD5934 is not connected directly to the VOUT SMB connector therefore Link 1 and Link 2 must be inserted...

Страница 5: ... Pin 6 of the AD5934 or an amplified version depending on the status of LK1 LK2 and LK6 assuming the presence of a user supplied external op amp at U1 see Figure 1 VIN This connector takes the response signal current from across the impedance being analyzed ZUNKNOWN which is connected between the VIN and VOUT SMB connectors and provides a path back to the input pin VIN Pin 5 Link 7 must be inserte...

Страница 6: ... LK10 LK5 C25 10µF C26 0 1µF C30 10µF C28 0 1µF C2 10µF C24 0 1µF C29 10µF C27 0 1µF LK8 LK9 C42 15pF VOUT VIN VDD_AMP R4 R3 R1 50Ω DGND CLK1 DGND VDD O P GND XTAL1 C1 0 1nF 4 3 2 DVDD_5V AVDD_SIG AVDD_REF DGND DVDD_5V LK1 DGND DGND T7 T8 SCL SDA VDD_REF AGND DGND AD820 U1 OUT LK4 R2 LK11 5VUSB NC NO CONNECT TEST IMPEDANCE FEEDBACK RESISTOR C41 Figure 2 Setup Link Position Circuit A 15 pF Capacito...

Страница 7: ...VIN Input to Receive Transimpedance Amplifier Presents a virtual earth voltage of VDD 2 6 VOUT Excitation Voltage Signal Output 8 MCLK Master Clock for the System User Supplied 9 DVDD Digital Supply Voltage 10 AVDD1 Analog Supply Voltage 1 11 AVDD2 Analog Supply Voltage 2 12 DGND Digital Ground 13 AGND1 Analog Ground 1 14 AGND2 Analog Ground 2 15 SDA I2 C Data Input Open drain pins requiring 10 kΩ...

Страница 8: ...ent operating system settings See the Step 2 Connect the USB Cable section 3 Ensure that the appropriate links are made throughout the evaluation board Power up the evaluation board appropriately prior to opening and running the evaluation software program See the Step 3 Verify the Links and Power Up section 4 Configure the main dialog box of the evaluation board software to run the required sweep...

Страница 9: ... Error Message STEP 2 CONNECT THE USB CABLE Plug one end of the USB cable into the computer USB hub and connect the other end to the AD5934 evaluation board USB socket see J1 in Figure 37 A message may appear informing you that a USB device has been detected on the host computer and that new hardware has been found see Figure 10 05449 010 Figure 10 USB Device Detected by Host Computer The Found Ne...

Страница 10: ...terface panel along with a frequency sweep impedance profile for a 200 kΩ resistive impedance note that RFB 200 kΩ This section describes how to set up a typical sweep across a 200 kΩ impedance when RFB 200 kΩ using the installed AD5934 software The theory of operation and the internal system architecture of the AD5934 device are described in detail in the AD5934 data sheet This is available at ww...

Страница 11: ... is accurately measured calibration impedance connected between the VIN and VOUT pins of the AD5934 The choice of calibration impedance topology for example R1 in series with C1 R1 in parallel with C1 etc depends on the application in question However you must ensure that each component of the measured calibration impedance is entered correctly into each chosen topology component text box see Arro...

Страница 12: ...or example if you change the output excitation range PGA gain etc after the system has been calibrated that is after the gain factor s have been calculated it is necessary to recalculate the gain factor s in order to sub sequently obtain accurate impedance measurement results The gain factor s calculated in software are not programmed into the AD5934 RAM and are only valid when the evaluation soft...

Страница 13: ...uced through the output amplifiers the receive I V amplifier the low pass filter etc along with the phase through the impedance ZØ being analyzed which is connected between VOUT and VIN Pin 6 and Pin 5 of the AD5934 The phase of the system must be calibrated using a resistor before any subsequent impedance phase ZØ measurement can be calculated You need to perform the calibration with a resistor i...

Страница 14: ...e AD5934 device drivers have not been installed to the correct registry and therefore cannot be correctly located by the install wizard To reinstall the device drivers right click My Computer and then left click Properties On the Hardware tab choose Device Manager Expand Other devices see Figure 24 Right click USB Device and then left click Uninstall Driver Unplug the evaluation board and wait app...

Страница 15: ... the flowchart will be explained with the help of Visual Basic code extracts The evaluation board source code Visual Basic is available upon request from the Analog Devices Technical Support Center The firmware code C code which is downloaded to the USB microcontroller connected to the AD5934 implements the low level I2 C signal control that is read and write vendor requests The Evaluation Board S...

Страница 16: ...p frequency Dim Increment As Long used as a temporary counter Dim i As Integer used as a temporary counter in max min mag phase loop Dim xy As Variant used in the stripx profile Dim varray As Variant Dim Gainfactor as double either a single mid point calibration or an array of calibration points Dim TempStartFrequency As Double Dim StartFrequencybyte0 As Long Dim StartFrequencybyte2 As Long Dim St...

Страница 17: ...ts in the sweep Frequency StartFrequency the sweep starts from here PROGRAM 30K Hz to the START FREQUENCY register DDSRefClockFrequency 16E6 Assuming a 16M Hz clock connected to MCLK StartFrequency 30E3 frequency sweep starts at 30K Hz TempStartFrequency StartFrequency DDSRefClockFrequency 16 2 27 dial up code for the DDS TempStartFrequency Int TempStartFrequency 30K Hz 3D70A3 hex StartFrequencyby...

Страница 18: ...Register H80 H10 msDelay 2 this is a user determined delay dependant upon the network under analysis 2ms delay Start the frequency sweep Start Frequency Sweep WritetToControlRegister H80 H20 Enter Frequency Sweep Loop ReadbackStatusRegister PortRead HD H8F ReadbackStatusRegister ReadbackStatusRegister And H4 mask off bit D2 i e is the sweep complete Do While ReadbackStatusRegister 4 And Increment ...

Страница 19: ... this is determined at calibration see gain factor section and Datasheet Impedance 1 Magnitude GainFactor Write Data to each global array MagnitudeArray IndexArray Impedance PhaseArray IndexArray sweep_phase ImagineryDataArray IndexArray ImagineryData code IndexArray Magnitude RealDataArray IndexArray RealData Increment Increment 1 increment was set to number of increments of sweep at the start Fr...

Страница 20: ...2 V p p The peak to peak voltage presented to the ADC input is 2 V p p However if a programmable gain amplifier setting gain of 5 is chosen the voltage saturates the ADC and as a result the calculated calibration term that is the gain factor is inaccurate The gain factor should be calculated when the largest response signal is presented to the ADC while ensuring that the signal is maintained withi...

Страница 21: ... Resistance Value Typ Range 1 2 V p p 200 Ω Range 2 1 V p p 2 4 kΩ Range 3 0 4 V p p 1 0 kΩ Range 4 0 2 V p p 600 Ω Therefore to accurately calibrate the AD5934 to measure small impedances it is necessary to reduce the signal current by sufficiently attenuating the excitation voltage and to account for the output series resistance value ROUT by factoring it into the gain factor calculation see the...

Страница 22: ...DDS core and DAC which together generate the excitation signal used to measure the impedance ZUNKNOWN The DDS core has a 27 bit phase accumulator allowing subhertz 0 1 Hz frequency resolution The output of the phase accumulator is connected to the input of a read only memory ROM The digital output of the phase accumulator is used to address individual memory locations in the ROM The digital conten...

Страница 23: ...es the 1024 samples required for the single point DFT to cover an integer number of periods of the current excitation frequency SAMPLES SPAN ENTIRE EXCITATION PERIOD SAMPLE WINDOW DFT ASSUMES A PERIODIC SAMPLE SET 05449 029 Figure 29 Sample Set Spanning the Entire Excitation Period SAMPLES DO NOT SPAN ENTIRE EXCITATION PERIOD DFT ASSUMES A PERIODIC SAMPLE SET 05449 030 Figure 30 Sample Set not Spa...

Страница 24: ...er ADC conversion clock speed and the upper excitation limit is now restricted to 7 8125 kHz Measuring Higher Excitation Frequencies The AD5934 is specified to a typical system accuracy of 0 5 within the frequency range of 1 kHz up to 100 kHz assuming the AD5934 system is calibrated correctly for the impedance range being tested The lower frequency limit is determined by the value of the system cl...

Страница 25: ...s on the transmit and receive sides of the AD5934 the low pass filter and the impedance connected between the VOUT and VIN pins of the AD5934 The parameters of interest for many users of the AD5934 are the magnitude of the impedance ZUNKNOWN and the impedance phase ZØ The measurement of the impedance phase ZØ is a two step process The first step involves calculating the AD5934 system phase The AD5...

Страница 26: ...rd phase angle is dependant on the sign of the real and imaginary components see Table 7 for a summary Figure 34 System Phase Response vs Capacitive Phase Table 7 Phase Angle 100 90 80 70 60 50 0 40 30 20 10 PHASE Degrees 0 15k 30k 45k 60k 75k 90k 105k 120k FREQUENCY Hz 05449 035 Real Imaginary Quadrant Phase Angle Degrees Positive Positive First π 180 tan 1 R I Positive Negative Second π 180 tan ...

Страница 27: ...Preliminary Technical Data EVAL AD5934EB Rev PrC Page 27 of 32 EVALUATION BOARD SCHEMATIC 05449 036 Figure 36 Schematic ...

Страница 28: ...EVAL AD5934EB Preliminary Technical Data Rev PrC Page 28 of 32 05449 037 Figure 37 Schematic ...

Страница 29: ...Preliminary Technical Data EVAL AD5934EB Rev PrC Page 29 of 32 05449 038 Figure 38 05449 039 Figure 39 Schematic ...

Страница 30: ...EVAL AD5934EB Preliminary Technical Data Rev PrC Page 30 of 32 ORDERING INFORMATION ORDERING GUIDE Model Description EVAL AD5934EB Evaluation Board ESD CAUTION ...

Страница 31: ...Preliminary Technical Data EVAL AD5934EB Rev PrC Page 31 of 32 NOTES ...

Страница 32: ...934EB Preliminary Technical Data Rev PrC Page 32 of 32 NOTES 2005 2007 Analog Devices Inc All rights reserved Trademarks and registered trademarks are the property of their respective owners EB05449 0 7 07 PrC ...

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