Analog Devices AD5934 Manual
  1. Manuals
  2. Brands
  3. Analog Devices Manuals
  4. Measuring Instruments
  5. AD5934
  6. Manual
Analog Devices AD5934 Manual

Analog Devices AD5934 Manual

Hide thumbs
Table of Contents

Advertisement

Quick Links

Download this manual

FEATURES

Programmable output peak-to-peak excitation voltage
to a maximum frequency of 100 kHz
Programmable frequency sweep capability with
2
serial I
C interface
Frequency resolution of 27 bits (<0.1 Hz)
Impedance measurement range from 1 kΩ to 10 MΩ
Capable of measuring 100 Ω to 1 kΩ with additional circuitry
Phase measurement capability
System accuracy of 0.5%
2.7 V to 5.5 V power supply operation
Temperature range: −40°C to +125°C
16-lead SSOP package

APPLICATIONS

Electrochemical analysis
Bioelectrical impedance analysis
Impedance spectroscopy
Complex impedance measurement
Corrosion monitoring and protection equipment
Biomedical and automotive sensors
Proximity sensing
Nondestructive testing
Material property analysis
Fuel/battery cell condition monitoring
MCLK
SCL
INTERFACE
SDA
REAL
REGISTER
1024-POINT DFT
Rev. A
Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other
rights of third parties that may result from its use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarks and registered trademarks are the property of their respective owners.
250 kSPS, 12-Bit Impedance Converter,

FUNCTIONAL BLOCK DIAGRAM

AVDD
DVDD
DDS
CORE
(27 BITS)
2
I
C
IMAGINARY
REGISTER
ADC
(12 BITS)
AGND
DGND

GENERAL DESCRIPTION

The AD5934 is a high precision impedance converter system
solution that combines an on-board frequency generator with a
12-bit, 250 kSPS, analog-to-digital converter (ADC). The
frequency generator allows an external complex impedance to
be excited with a known frequency. The response signal from
the impedance is sampled by the on-board ADC and a discrete
Fourier transform (DFT) is processed by an on-board DSP
engine. The DFT algorithm returns a real (R) and imaginary (I)
data-word at each output frequency.
Once calibrated, the magnitude of the impedance and relative
phase of the impedance at each frequency point along the sweep
is easily calculated using the following two equations:
Magnitude =
Phase = tan
A similar device, available from Analog Devices, Inc., is the
AD5933, which is a 2.7 V to 5.5 V, 1 MSPS, 12-bit impedance
converter, with an internal temperature sensor, available in a
16-lead SSOP.
DAC
V
BIAS
AD5934
GAIN
LPF
Figure 1.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
Fax: 781.461.3113
Network Analyzer
R +
2
2
I
−1
(I/R)
R
VOUT
OUT
Z(ω)
RFB
VIN
VDD/2
©2005–2008 Analog Devices, Inc. All rights reserved.
AD5934
www.analog.com

Advertisement

Table of Contents
loading
Need help?

Need help?

Do you have a question about the AD5934 and is the answer not in the manual?

Questions and answers

Subscribe to Our Youtube Channel

Related Manuals for Analog Devices AD5934

Summary of Contents for Analog Devices AD5934

  • Page 1: Features

    Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.

  • Page 2: Table Of Contents

    Sensor/Complex Impedance Measurement......31 Gain Factor Calculation ............15 Electro-Impedance Spectroscopy..........31 Impedance Calculation Using Gain Factor......15 Choosing a Reference for the AD5934 ........32 Gain Factor Variation with Frequency ........15 Layout and Configuration............. 33 2-Point Calibration..............16 Power Supply Bypassing and Grounding........

  • Page 3: Revision History

    AD5934 REVISION HISTORY 5/8—Rev. 0 to Rev. A Added Table 6; Renumbered Sequentially........20 Changes to Layout.............. Universal Deleted Table 8 ................19 Changes to Features Section, General Description Section, and Deleted Table 10 and Table 11 ............20 Figure 1 ....................1 Changes to Table 9 ................22 Deleted Table 1;...

  • Page 4: Specifications

    AD5934 SPECIFICATIONS VDD = 3.3 V, MCLK = 16.776 MHz, 2 V p-p output excitation voltage @ 30 kHz, 200 kΩ connected between Pin 5 and Pin 6; feedback resistor = 200 kΩ connected between Pin 4 and Pin 5; PGA gain = ×1, unless otherwise noted.
  • Page 5 Temperature range for Y version = −40°C to +125°C, typical at +25°C. The lower limit of the output excitation frequency can be lowered by scaling the clock supplied to the AD5934. The peak-to-peak value of the ac output excitation voltage scales with supply voltage according to the following formula. VDD is the supply voltage.

  • Page 6: I C Serial Interface Timing Characteristics

    AD5934 C SERIAL INTERFACE TIMING CHARACTERISTICS VDD = 2.7 V to 5.5 V; all specifications T to T , unless otherwise noted (see Figure 2). Table 2. Unit Description Parameter Limit at T kHz max SCL clock frequency μs min SCL cycle time μs min...

  • Page 7: Absolute Maximum Ratings

    AD5934 ABSOLUTE MAXIMUM RATINGS = 25°C, unless otherwise noted. Table 3. Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress Parameter Rating rating only; functional operation of the device at these or any DVDD to GND −0.3 V to +7.0 V...

  • Page 8: Pin Configuration And Function Descriptions

    AD5934 PIN CONFIGURATION AND FUNCTION DESCRIPTIONS AD5934 AGND2 AGND1 TOP VIEW (Not to Scale) DGND VOUT AVDD2 AVDD1 MCLK DVDD NC = NO CONNECT NOTES: 1. IT IS RECOMMENDED TO TIE ALL SUPPLY CONNECTIONS (PIN 9, PIN 10, AND PIN 11) AND RUN FROM A SINGLE SUPPLY BETWEEN 2.7V AND 5.5V.

  • Page 9: Typical Performance Characteristics

    AD5934 TYPICAL PERFORMANCE CHARACTERISTICS MEAN = 1.9824 MEAN = 0.7543 SIGMA = 0.0072 SIGMA = 0.0099 1.92 1.94 1.96 1.98 2.00 2.02 2.04 2.06 0.68 0.70 0.72 0.74 0.76 0.78 0.80 0.82 0.84 0.86 VOLTAGE (V) VOLTAGE (V) Figure 4. Range 1 Output Excitation Voltage Distribution, VDD = 3.3 V Figure 7.
  • Page 10 AD5934 15.8 MEAN = 0.1982 AVDD1, AVDD2, DVDD CONNECTED TOGETHER 15.3 SIGMA = 0.0008 OUTPUT EXCITATION FREQUENCY = 30kHz RFB, Z = 100kΩ CALIBRATION 14.8 14.3 13.8 13.3 12.8 12.3 11.8 11.3 10.8 0.192 0.194 0.196 0.198 0.200 0.202 0.204 0.206...

  • Page 11: Teminology

    TEMINOLOGY Total System Accuracy Signal-to-Noise Ratio (SNR) The AD5934 can accurately measure a range of impedance SNR is the ratio of the rms value of the measured output signal values to less than 0.5% of the correct impedance value for to the rms sum of all other spectral components below the supply voltages between 2.7 V to 5.5 V.

  • Page 12: System Description

    Figure 14. Block Overview The AD5934 is a high precision, impedance converter system The AD5934 permits the user to perform a frequency sweep with solution that combines an on-board frequency generator with a a user-defined start frequency, frequency resolution, and number 12-bit, 250 kSPS ADC.

  • Page 13: Transmit Stage

    Frequency Increment This is a 24-bit word that is programmed to the on-board RAM at As shown in Figure 16, the transmit stage of the AD5934 is made Register Address 0x85, Register Address 0x86, and Register Address up of a 27-bit phase accumulator DDS core that provides the output 0x87 (see the Register Map section).

  • Page 14: Frequency Sweep Command Sequence

    The digital data from the ADC is passed directly to the DSP core frequency point (see Figure 30). of the AD5934 that performs a DFT on the sampled data. The DDS output signal is passed through a programmable DFT OPERATION gain stage to generate the four ranges of peak-to-peak output excitation signals listed in Table 5.

  • Page 15: Impedance Calculation

    To convert this number into impedance, it must be multiplied by a scaling factor called the gain factor. The gain factor is Because the AD5934 has a finite frequency response, the gain calculated during the calibration of the system with a known factor also shows a variation with frequency.

  • Page 16: 2-Point Calibration

    AD5934 2-POINT CALIBRATION GAIN FACTOR SETUP CONFIGURATION Alternatively, it is possible to minimize this error by assuming When calculating the gain factor, it is important that the receive that the frequency variation is linear and adjusting the gain stage is operating in its linear region. This requires careful selection factor with a 2-point calibration.

  • Page 17: Gain Factor Temperature Variation

    Minimizing the impedance range under test optimizes the AD5934 measurement performance. Following are the examples of = 1kΩ CALIBRATION IMPEDANCE = 1kΩ the AD5934 performance when operating in the six different = 25°C impedance ranges. The gain factor is calculated with a precision 5kΩ...
  • Page 18 AD5934 Impedance Range 3 (10 kΩ to 100 kΩ) Impedance Range 5 (1 MΩ to 2 MΩ) The following conditions were used to conduct the tests shown The following conditions were used to conduct the tests shown in Figure 24:...

  • Page 19: Measuring The Phase Across An Impedance

    AD5934 signal path, and the resulting phase is due entirely For example, it is a common misconception to assume that if a to the internal poles of the AD5934, that is, the system phase. user was analyzing a series RC circuit that the real value stored...
  • Page 20 AD5934 component is negative, that is, the data lies in the second quadrant, the arctangent formula returns a negative angle, and it is necessary to add an additional 180° to calculate the correct 220kΩ RESISTOR standard angle. Likewise, when the real and imaginary components...

  • Page 21: Performing A Frequency Sweep

    INTO RELEVANT REGISTERS (1) START FREQUENCY REGISTER (2) NUMBER OF INCREMENTS REGISTER (3) FREQUENCY INCREMENT REGISTER PLACE THE AD5934 INTO STANDBY MODE. RESET: BY ISSUING A RESET COMMAND TO THE CONTROL REGISTER, THE DEVICE IS PLACED IN STANDBY MODE. PROGRAM INITIALIZE WITH START FREQUENCY COMMAND TO THE CONTROL REGISTER.

  • Page 22: Register Map

    Table 9. D11 and D8 to D0 Control Register Map REGISTER ADDRESS 0x81) Bits Description The AD5934 contains a 16-bit control register (Register Address No operation 0x80 and Register Address 0x81) that sets the control modes. PGA gain; 0 = ×5, 1 = ×1 The default value of the control register upon reset is as follows: Reserved;...

  • Page 23: Start Frequency Register (Register Address 0X82, Register Address 0X83, Register Address 0X84)

    DSP. follows: D23 to D0 are not reset at power-up. After the reset When the AD5934 receives this command, it waits for the command, the contents of this register are not reset.

  • Page 24: Number Of Increments Register (Register Address 0X88, Register Address 0X89)

    Each of the bits from D7 to stored D0 indicate the status of a specific functionality of the AD5934. in binary format Bit D0 and Bit D4 to Bit D7 are treated as don’t care bits; these bits do not indicate the status of any measurement.

  • Page 25: Real And Imaginary Data Registers (16 Bits-Register Address 0X94, Register Address 0X95, Register Address 0X96, Register Address 0X97)

    AD5934 Valid Real/Imaginary Data REAL AND IMAGINARY DATA REGISTERS (16 BITS— REGISTER ADDRESS 0x94, REGISTER ADDRESS This bit is set when data processing for the current frequency 0x95, REGISTER ADDRESS 0x96, REGISTER point is finished, indicating real/imaginary data available for ADDRESS 0x97) reading.

  • Page 26: Serial Bus Interface

    The be from the master or slave device. Data transitions on the data AD5934 has a 7-bit serial bus slave address. When the device is line must occur during the low period of the clock signal and powered up, it has a default serial bus address, 0001101 (0x0D).

  • Page 27: Writing/Reading To The Ad5934

    AD5934. The figures in this Figure 32. Writing Register Data to Register Address section use the abbreviations shown in Table 14. In the AD5934, the write byte protocol is also used to set a Table 14. I C Abbreviation Table pointer to a register address (see Figure 33).

  • Page 28: Read Operations

    Receive Byte The master device asserts a start condition on SDA. In the AD5934, the receive byte protocol is used to read a single The master sends the 7-bit slave address followed by the byte of data from a register address whose address has previously write bit (low).

  • Page 29: Typical Applications

    Figure 37. The aim of this the output series resistance is comparable to the value of the circuit is to place the AD5934 system gain within its linear impedance under test (Z ). If the R...

  • Page 30: Biomedical: Noninvasive Blood Impedance Measurement

    = 100 Ω UNKNOWN The AD5934 can be used to inject a stimulus signal through the PGA setting = ×1 blood sample via a probe. The response signal is analyzed and To attenuate the excitation voltage at VOUT, choose a ratio the effective impedance of the blood is tabulated.

  • Page 31: Sensor/Complex Impedance Measurement

    The impedance of the loop is monitored constantly. If a car is parked over the coil, the impedance of the coil changes and the AD5934 detects the presence of the car. Rev. A | Page 31 of 40...

  • Page 32: Choosing A Reference For The Ad5934

    AD5934 are shown in Table 17. Because the supply current required by the AD5934 is extremely low, the parts are ideal for low supply applications. The ADR395 voltage reference is recommended in this case.

  • Page 33: Layout And Configuration

    When traces cross on opposite sides of the board, area of the board. If the AD5934 is in a system where other ensure that they run at right angles to each other to reduce feed- devices require an AGND-to-DGND connection, the connection through effects on the board.

  • Page 34: Evaluation Board

    The evaluation board is a test system designed to simplify the minimum effort. evaluation of the AD5934. The evaluation board data sheet that The evaluation board interfaces to the USB port of a PC. It is is available with the evaluation board gives full information on possible to power the entire board from the USB port.

  • Page 35: Schematics

    AD5934 SCHEMATICS Figure 40. EVAL-AD5934EBZ USB Schematic Rev. A | Page 35 of 40...
  • Page 36 AD5934 Figure 41. EVAL-AD5934EBZ Schematic Rev. A | Page 36 of 40...
  • Page 37 AD5934 Figure 42. Linear Regulator on EVAL-AD5934EBZ Rev. A | Page 37 of 40...
  • Page 38 AD5934 Figure 43. Decoupling on the EVAL-AD5934EBZ Rev. A | Page 38 of 40...

  • Page 39: Bill Of Materials

    USB microcontroller, Cypress CY7C68013A-56LFXC, LFCSP-56 Digi-Key 428-1669-ND ADR425, 0 V reference SO8NB ADR425ARZ ADP3303-3.3 precision low dropout voltage regulator SO8NB ADP3303ARZ-3.3 AD5933/AD5934 SSOP16 AD5933YRSZ/AD5934YRSZ CM309S SMD crystal 24 MHz FEC 9509658 3.3 V, 16 MHz clock oscillator AEL-4313 Stick-on feet ×4...

  • Page 40: Outline Dimensions

    Z = RoHS Compliant Part. Purchase of licensed I C components of Analog Devices or one of its sublicensed Associated Companies conveys a license for the purchaser under the Philips I C Patent Rights to use these components in an I C system, provided that the system conforms to the I C Standard Specification as defined by Philips.

Table of Contents