Datasheet AD7323 Datasheet (Analog Devices)

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500 ksps, 4-Channel, Software Selectable

Preliminary Technical Data

FEATURES

• 12-Bit plus Sign SAR ADC

• True Bipolar Input Ranges

• Software Selectable Input Ranges

± 10V, ± 5V, ± 2.5V, 0 to 10V

• 500 kSPS Throughput Rate

• Four Analog Input Channels with Channel Sequencer

• Single Ended, True Differential and Pseudo Differential

Analog Input Capability

• High Analog Input Impedance

• Low Power: 12 mW

• Full Power Signal Bandwidth: 7 MHz

• Internal 2.5 V Reference

• High Speed Serial Interface SPI/QSPI/DSP/MICROWIRE

Compatible

• Power Down Modes

• 16-Lead TSSOP package

• iCMOS

• For eight and two channel equivalent devices see

Process Technology

AD7327 and AD7321 respectively.

True bipolar Input, 12-Bit Plus Sign ADC

AD7323*

FUNCTIONAL BLOCK DIAGRAM

Figure 1.

GENERAL DESCRIPTION

The AD7323 is a 4-Channel, 12-Bit plus Sign Successive Approximation ADC. The ADC has a high speed serial interface that can operate at throughput rates up to 500 kSPS.

The AD7323 can accept true bipolar Analog Input signals. The AD7323 has four software selectable inputs Ranges, ±10V, ±5V, ±2.5V and 0 to 10V. Each analog input channel can be independently programmed to one of the four input ranges.

The Analog input channels on the AD7323 can be programmed to be Single-Ended, true Differential or Pseudo Differential.

The AD7323 contains a 2.5V Internal reference. The AD7323 also allows for external Reference operation. If a 3V reference is applied the REF ±12V Analog Input. Minimum V required for the ±12V Input Range.

* Protected by U.S. Patent No. 6,731,232

iCMOS

Process Technology For analog systems designers within industrial/instrumentation equipment OEMs who need high performance ICs at higher-voltage levels, iCMOS is a technology platform that enables the development of analog ICs capable of 30V and operating at +/- 15V supplies while allowing dramatic reductions in power consumption and package size, and increased AC and DC performance.

pin, the AD7323 can accept a true Bipolar

IN/OUT

and VSS supplies of ±12V are

PRODUCT HIGHLIGHTS

1. The AD7323 can accept True Bipolar Analog Input signals, ±10V, ±5V, ±2.5V and 0 to 10V unipolar signals.

2. The Four Analog Inputs can be configured as 4 Single-Ended inputs, 2 True Differential, 2 Pseudo Differential or 3 Pseudo Differential Inputs. The AD7323 has high Impedance Analog Inputs.

3. The AD7323 features a High Speed Serial Interface. Throughput Rates up to 500 kSPS can be achieved on the AD7323.

4. Low Power, 26 mW at maximum throughput rate of 500 kSPS.

Device Number

AD7328 1000 12 bit + Sign 8 AD7327 500 12 bit + Sign 8 AD7324 1000 12 bit + Sign 4 AD7323 500 12 bit + Sign 4 AD7322 1000 12 bit + Sign 2 AD7321 500 12 bit + Sign 2

Throughput Rate - ksps

Number of bits Number of

Channels

Rev. PrA

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 companies.

www.analog.com

AD7323 Preliminary Technical Data

TABLE OF CONTENTS

AD7323—Specifications.................................................................. 3

Absolute Maximum Ratings............................................................ 6

Pin Functional Descriptions ....................................................... 7

Terminology ...................................................................................... 8

REVISION HISTORY

Revision PrA: Preliminary Version

Theory of Operation.....................................................................9

AD7323 Registers ........................................................................... 12

Serial interface ................................................................................ 21

OUTLINE DIMENSIONS.................................................................. 22

Rev. PrA| Page 2 of 22

AD7323 Preliminary Technical Data

AD7323—SPECIFICATIONS

Table 1. Unless otherwise noted, VDD = + 12V to +16.5V, VSS = -12V to –16.5V, VCC = 2.7V to 5.25V, V

2.5V Internal/External, f

Parameter Specification Units Test Conditions/Comments

DYNAMIC PERFORMANCE F

Signal to Noise Ratio (SNR)

Signal to Noise + Distortion (SINAD)2 75 dB min Differential Mode

71.5 dB min Single-Ended/Pseudo Differential Mode Total Harmonic Distortion (THD) Peak Harmonic or Spurious Noise

(SFDR)

Intermodulation Distortion (IMD)

Second Order Terms -88 dB typ

Third Order Terms Aperature Delay Aperature Jitter2

Common Mode Rejection (CMRR) Channel-to-Channel Isolation Full Power Bandwidth

DC ACCURACY

Resolution 12+Sign Bits Integral Nonlinearity Differential Nonlinearity Offset Error3 ±8 LSB max Unipolar Range with Straight Binary output coding Offset Error Match2 ±0.5 LSB max Gain Error Gain Error Match

Positive Full-Scale Error Positive Full Scale Error Match Bipolar Zero Error

Bipolar Zero Error Match Negative Full Scale Error2 ±4 LSB max Negative Full Scale Error Match

ANALOG INPUT See Table 5

Input Voltage Ranges (Programmed via Range Register)

DC Leakage Current ±10 nA max Input Capacitance 12 pF typ When in Track, ±10V Range 15 pF typ When in Track, ±5V, 0 to 10V Range 20 pF typ When in Track, ±2.5V Range 3 pF typ When in Hold

REFERENCE INPUT/OUTPUT

Input Voltage Range +2.5 to +3 V min to max Input DC Leakage Current ±1 µA max Input Capactiance 20 pF typ Reference Output Voltage 2.49/2.51 Vmin/max Reference Temperature Coefficient 25 ppm/°C max 10 ppm/°C typ Reference Output Impedance 25

= 10 MHz, fS = 500 kSPS TA = T

SCLK

= 2.7V to 5.25V, V

DRIVE

to T

MAX

MIN

= 50 kHz Sine Wave

76 dB min Differential Mode 72 dB min Single-Ended /Pseudo Differential Mode

-80 dB max

-80 F

dB max

= 40.1 kHz, Fb = 41.5 kHz

-88 dB typ 10 ns max 50 ps typ

TBD dB typ

-80 dB typ F 7

1.5

MHz typ MHz typ

= 400 kHz

@ 3 dB @ 0.1 dB

±1.5 LSB max ± 0.95 LSB max Guaranteed No Missing Codes to 13-Bits

±6 LSB max ±0.6 LSB max ±3 LSB max Bipolar Range with Twos Complement Output Coding ±0.6 LSB max ±8 LSB max ±0.5 LSB max

±0.5 LSB max

±10 ±5 ±2.5 0 to 10

V V V V

Ω typ

= +10V min , VSS = -10V min, VCC = 2.7V to 5.25V

= +5V min, VSS = -5V min, VCC = 2.7V to 5.25V

= +5V min, VSS = - 5V min, VCC = 2.7V to 5.25V

= +10V min, VSS = 0 V min, VCC = 2.7V to 5.25V

REF

Rev. PrA | Page 3 of 22

AD7323 Preliminary Technical Data

Parameter Specification Units Test Conditions/Comments

LOGIC INPUTS

Input High Voltage, V Input High Voltage, V

0.4 V max V Input Current, IIN ± 1 µA max VIN = 0V or VCC

Input Capacitance, C

LOGIC OUTPUTS

Output High Voltage, VOH V Output Low Voltage, VOL 0.4 V max I Floating State Leakage Current ±1 µA max Floating State Output Capacitance

Output Coding

CONVERSION RATE

Conversion Time 1.6 µs max 16 SCLK Cycles with SCLK = 10 MHz Track-and-Hold Acquisition Time 250 ns min Sine Wave Input 250 ns min Full Scale Step input Throughput Rate 500 kSPS max See Serial Interface section

POWER REQUIREMENTS Digital Inputs = 0V or VCC

2.7V/5.25V V min/max

DRIVE

Normal Mode IDD 300 µA max V ISS 370 µA max V ICC 2 mA max V Auto-Standby Mode F IDD TBD µA max ISS TBD µA max ICC 1.6 mA typ Auto-Standby Mode F IDD TBD µA max ISS TBD µA max ICC 1 mA typ Full Shutdown Mode IDD 0.9 µA max ISS 0.9 µA max ICC 0.9 µA max SCLK On or Off POWER DISSIPATION Normal Mode 26 mW max V 12 mW typ V Full Shutdown Mode 35 µW max V

NOTES

Temperature ranges as follows: -40°C to +85°C

See Terminology

Guaranteed by Characterization

Functional from VDD = +4.75V and VSS = -4.75V

Specifications subject to change without notice.

2.4 V min

INH

0.8 V max V

INL

10 pF max

- 0.2V V min I

DRIVE

10 pF max Straight

Coding bit set to 1 in Control Register

= 4.75 to 5.25 V

= 2.7 to 3.6 V

= 200 µA

SOURCE

= 200 µA

SINK

Natural Binary

Two’s

Coding bit set to 0 in Control Register

Complement

12V/+16.5V V min/max See Table 5

-12V/16.5V V min/max See Table 5

2.7V / 5.25V V min/max See Table 5

= +16.5V

= -16.5V

= 5.25V

= TBD

SAMPLE

= TBD

SAMPLE

= +16.5V, VSS = -16.5V, V

= +5V, VSS = -5V, V

= +16.5V, VSS = -16.5V, V

= 5V,

= 5.25V,

Rev. PrA| Page 4 of 22

AD7323 Preliminary Technical Data

TIMING SPECIFICATIONS

Table 2. Unless otherwise noted, V Internal/External, T

Parameter Limit at T

SCLK

= T

MIN

MAX

to T

, T

20 kHz min

= +12V to + 16.5V, VSS = -12V to –16.5V, V

MIN

Unit Description

MAX

10 MHz max t

CONVERT

50 ns max

QUIET

t1 10 ns min

t5 0.4t t6 0.4t t

16×t

ns max T

SCLK

= 1/f

SCLK

Minimum Time between End of Serial Read and Next Falling Edge of CS

Minimum CS Pulse width

10 ns min

20 ns max

to SCLK Setup Time

Delay from CS until D

TBD ns max Data Access Time after SCLK Falling Edge.

SCLK

ns min SCLK High Pulsewidth

SCLK

ns min SCLK Low Pulsewidth

10 ns min SCLK to Data Valid Hold Time

25 ns max SCLK Falling Edge to D 10 ns min SCLK Falling Edge to D t

1 µs max Power up from Auto Standby

powerup

TBD ns min DIN set-up time prior to SCLK falling edge

5 ns min DIN hold time after SCLK falling edge

TBD µs max Power up from Full Shutdown/Auto Shutdown Mode

Three-State Disabled

OUT

High Impedance

OUT

High Impedance

OUT

=2.7V to 5.25, V

DRIVE

= 2.5V

REF

+5

SCLK

DOUT

DIN

3-STATE

ZERO

WRITE

ADD1

2 ID BITS

Reg Sel1

convert

DB11

ADD0

Reg Sel2

SIGN

MSB

Figure 2. Serial Interface timing Diagram

DB10

DB2

DB1

LSB

DB0

3-STATE

DONTC

Rev. PrA | Page 5 of 22

AD7323 Preliminary Technical Data

ABSOLUTE MAXIMUM RATINGS

Table 3. TA = 25°C, unless otherwise noted

VDD to AGND, DGND -0.3 V to +16.5 V VSS to AGND, DGND +0.3 V to –16.5 V VCC to AGND, DGND -0.3V to +7V V

to VCC -0.3 V to VCC + 0.3V

DRIVE

AGND to DGND -0.3 V to +0.3 V Analog Input Voltage to AGND

Digital Input Voltage to DGND -0.3 V to +7 V Digital Output Voltage to GND -0.3 V to V REFIN to AGND -0.3 V to VCC +0.3V Input Current to Any Pin Except Supplies

Operating Temperature Range -40°C to +85°C Storage Temperature Range -65°C to +150°C Junction Temperature +150°C TSSOP Package θJA Thermal Impedance 143 °C/W θJC Thermal Impedance 45 °C/W Pb-free Temperature, Soldering

Reflow 260(+0)°C

ESD TBD

Transient currents of up to 100 mA will not cause SCR latch-up.

-0.5V to VDD +

DRIVE

±10mA

0.5V

+0.3V

Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional operation of the device at these or any other conditions above those listed in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.

Rev. PrA | Page 6 of 22

AD7323 Preliminary Technical Data

PIN FUNCTIONAL DESCRIPTIONS

Figure 3. AD7323 Pin Configuration TSSOP

Table 4. AD7323 Pin Function Descriptions

Pin Mnemonic Pin Number Description

SCLK 16

OUT

DIN 2

AGND 4

REF

IN/

OUT

VCC 12

VDD 11 Positive power supply voltage. This is the positive supply voltage for the Analog Input section. VSS 6

13 The voltage applied to this pin determines the voltage at which the serial interface operates.

DRIVE

DGND 3,15 This is the Digital Ground Connection. Vin0-Vin3 7,8,9,10

Serial Clock. Logic Input. A serial clock input provides the SCLK used for accessing the data from the AD7323. This clock is also used as the clock source for the conversion process.

Serial Data Output. The conversion output data is supplied to this pin as a serial data stream. The bits are clocked out on the falling edge of the SCLK input and 16 SCLKs are required to access the data. The data stream consists of one leading zero followed by two channel identification bits, followed by the sign bit followed by the 12 bits of conversion data. The data is provided MSB first. See the Serial interface section.

Chip Select. Active low logic input. This input provides the dual function of initiating conversions on the AD7323 and frames the serial data transfer.

Data In. Data to be written to the on-chip registers is provided on this input and is clocked into the register on the falling edge of SCLK. See the AD7323 REGISTERS section.

Analog Ground. Ground reference point for all analog circuitry on the AD7323. All analog input signals and any external reference signal should be referred to this AGND voltage.

Reference Input/ Reference Output pin. The on-chip reference is available on this pin for use external to the AD7323. Alternatively, the internal reference can be disabled and an external reference applied to this input. When using the AD7323 with an external reference, the internal reference must be disabled via the control register. The nominal reference voltage is

2.5 V, which appears at the pin. A 470 nF decoupling capacitor should be placed on the Reference pin.

Analog Supply Voltage, 2.7 V to 5.25 V. This is the supply voltage for the ADC core on the AD7323. This supply should be decoupled to AGND.

Negative power supply voltage. This is the negavtive supply voltage for the Analog Input section.

Analog input 0 through Analog Input 3. The analog inputs are multiplexed into the on-chip track-and-hold. The analog input channel for conversion is selected by programming the channel address bits, ADD1 through ADD0, in the control register. The inputs can be configured as 4 Single-Ended Inputs, 2 True Differential Input pairs, 2 Pseudo Differential inputs or 3 Pseudo Differential Inputs. The configuration of the Analog inputs is selected by programming the Mode bits, Mode1 and Mode0, in the Control Register. The input range on each input channel is controlled by programming the range register. Input ranges of ±10V, ±5V, ±2.5V and 0 to 10V can be selected on each analog input channel. See the AD7323 REGISTERS section.

Rev. PrA | Page 7 of 22

AD7323 Preliminary Technical Data

TERMINOLOGY

Differential Nonlinearity This is the difference between the measured and the ideal 1 LSB change between any two adjacent codes in the ADC.

Integral Nonlinearity This is the maximum deviation from a straight line passing through the endpoints of the ADC transfer function. The endpoints of the transfer function are zero scale, a point 1 LSB below the first code transition, and full scale, a point 1 LSB above the last code transition.

Offset Code Error This applies to Straight Binary output coding. It is the deviation of the first code transition (00 . . . 000) to (00 . . . 001) from the ideal, i.e., AGND + 1 LSB.

Offset Error Match This is the difference in Offset Error between any two input channels.

Gain Error This applies to Straight Binary output coding. It is the deviation of the last code transition (111 . . . 110) to (111 . . . 111) from the ideal (i.e., 4 x V

– 1 LSB, 2 x V

REF

the offset error has been adjusted out.

Gain Error Match This is the difference in Gain Error between any two input channels.

Bipolar Zero Code Error This applies when using twos complement output coding and a bipolar Analog Input. It is the deviation of the midscale transition (all 1s to all 0s) from the ideal V

- 1 LSB.

Bipolar Zero Code Error Match This refers to the difference in Bipolar Zero Code Error between any two input channels.

Positive Full Sc ale Error This applies when using twos complement output coding and any of the bipolar Analog Input ranges. It is the deviation of the last code transition (011…110) to (011…111) from the ideal ( +4 x V

- 1 LSB, + 2 x V

REF

bipolar Zero Code Error has been adjusted out.

Positive Full Sc ale Error Match

This is the difference in Positive Full Scale error between any two input channels.

Negative Full Scale Error This applies when using twos complement output coding and any of the bipolar Analog Input ranges. This is the deviation of the first code transition (10…000) to (10…001) from the ideal

REF

– 1 LSB, + V

REF

–1 LSB, V

REF

–1 LSB) after

REF

voltage, i.e., AGND

– 1 LSB) after the

(i.e., - 4 x V

+ 1 LSB, - 2 x V

REF

the Bipolar Zero Code Error has been adjusted out.

Negative Full Scale Error Match

This is the difference in Negative Full Scale error between any two input channels.

Track-and-Hold Acquisition Time The track-and-hold amplifier returns into track mode after the fourteenth SCLK rising edge. Track-and-hold acquisition time is the time required for the output of the track-and-hold amplifier to reach its final value, within ±1/2 LSB, after the end of conversion.

Signal to (Noise + Distortion) Ratio

This is the measured ratio of signal to (noise + distortion) at the output of the A/D converter. The signal is the rms amplitude of the fundamental. Noise is the sum of all non-fundamental signals up to half the sampling frequency (f The ratio is dependent on the number of quantization levels in the digitization process; the more levels, the smaller the quantization noise. The theoretical signal to (noise + distortion) ratio for an ideal N-bit converter with a sine wave input is given by:

Signal to (Noise + Distortion) = (6.02N + 1.76) dB

Thus for a 13-bit converter, this is 80.02 dB.

Total Harmonic Distortion

Total harmonic distortion (THD) is the ratio of the rms sum of harmonics to the fundamental. For the AD7323 it is defined as:

dBTHD

where V V

is the rms amplitude of the fundamental and V2, V3,

, V5 and V6 are the rms amplitudes of the second through the

log20)(

sixth harmonics.

Peak Harmonic or Spurious Noise Peak harmonic or spurious noise is defined as the ratio of the rms value of the next largest component in the ADC output spectrum (up to fS/2 and excluding dc) to the rms value of the fundamental. Normally, the value of this specification is determined by the largest harmonic in the spectrum, but for ADCs where the harmonics are buried in the noise floor, it will be a noise peak.

Channel-to-Channel Isolation Channel-to-channel isolation is a measure of the level of crosstalk between any two channels. It is measured by applying a full-scale, TBD kHz sine wave signal to all unselected input channels and determining how much that signal is attenuated in the selected channel with a 50 kHz signal. The figure given is the worst-case across all eight channels for the AD7323.

REF

+ 1 LSB, - V

+ 1 LSB) after

REF

/2), excluding dc.

VVVVV

++++

Rev. PrA | Page 8 of 22

Preliminary Technical Data AD7323

Intermodulation Distortion

With inputs consisting of sine waves at two frequencies, fa and fb, any active device with non-linearities will create distortion products at sum and difference frequencies of mfa ± nfb where m, n = 0, 1, 2, 3, etc. Intermodulation distortion terms are those for which neither m nor n are equal to zero. For example, the second order terms include (fa + fb) and (fa – fb), while the third order terms include (2fa + fb), (2fa – fb), (fa + 2fb) and (fa – 2fb).

The AD7323 is tested using the CCIF standard where two input frequencies near the top end of the input bandwidth are used. In this case, the second order terms are usually distanced in frequency from the original sine waves while the third order terms are usually at a frequency close to the input frequencies. As a result, the second and third order terms are specified separately. The calculation of the intermodulation distortion is as per the THD specification where it is the ratio of the rms sum of the individual distortion products to the rms amplitude of the sum of the fundamentals expressed in dBs.

PSR (Power Supply Rejection) Variations in power supply will affect the full-scale transition but not the converter’s linearity. Power supply rejection is the maximum change in full-scale transition point due to a change in power supply voltage from the nominal value. See Typical Performance Curves.

Table 5. Reference and Supply Requirements for each Analog Input Range

Selected Analog Input Range (V)

±10

± 5

±2.5

0 to 10

Reference Voltage (V)

2.5 ±10 3/5 ±10

3.0 ±12 3/5 ±12

2.5 ±5 3/5 ±5

3.0 ±6 3/5 ±6

2.5 ±2.5 3/5 ±5

3.0 ±3 3/5 ±5

2.5 0 to 10 3/5 +10/AGND

3.0 0 to 12 3/5 +12/AGND

Full Scale Input Range(V)

AV (V)

Minimum VDD/V

(V)

In order to meet the specified performance specifications when the AD7323 is configured with the minimum V

and VSS

supplies for a chosen Analog input range the throughput rate should be decreased from the maximum throughput range. See typical performance curves.

The Analog Inputs Can be configured as either 4 Single-Ended inputs, 2 True Differential Inputs, 2 Pseudo Differential Inputs or 3 Pseudo Differential Inputs. Selection can be made by programming the Mode bits, Mode0 and Mode1, in the Control Register.

THEORY OF OPERATION

CIRCUIT INFORMATION

The AD7323 is a fast, 4-Channel, 12-Bit Plus Sign, Bipolar Input, Serial A/D converter. The AD7323 can accept bipolar input ranges that include ±10V, ±5V, ±2.5V. It can also accept 0 to 10V unipolar input range. A different Analog input range can be programmed on each analog input Channel via the on-chip range register. The AD7323 has a high speed serial interface that can operate at throughput rates up to 500 kSPS.

The AD7323 requires V

and V

voltage Analog input structure. These supplies must be equal to or greater than the Analog input range. See Table 5 for the minimum requirements on these supplies for each Analog Input Range. The AD7323 requires a low voltage 2.7V to 5.25 V V supply to power the ADC core.

dual supplies for the high

The serial clock input accesses data from the part but also provides the clock source for each successive approximation ADC. The AD7323 has an on-chip 2.5 V reference. However the AD7323 can also work with an external Reference. On power up the external reference operation is the default option. If the internal Reference is the preferred option the user must write to the reference bit in the control register to select the internal Reference operation.

The AD7323 also features power-down options to allow power saving between conversions. The power-down modes are selected by programming the on-chip Control Register, as described in the modes of operation section.

CONVERTER OPERATION The AD7323 is a successive approximation analog-to-digital converter, based around two capacitive DACs. Figure 4 and Figure 5 show simplified schematics of the ADCs in Single Ended Mode during the acquisition and conversion phase, respectively. Figure 6 and Figure 7 show simplified schematics of the ADCs in Differential Mode during acquisition and

conversion phase, respectively. The ADC is comprised of control logic, a SAR, and a capacitive DAC. In Figure 4 (the acquisition phase), SW2 is closed and SW1 is in position A, the comparator is held in a balanced condition, and the sampling capacitor array acquires the signal on the input.

Rev. PrA| Page 9 of 22

AD7323 Preliminary Technical Data

CAPACITIVE

DAC

CONTROL

LOGIC

Vin0

AGND

SW1

COMPARATOR

SW2

Figure 4. ADC Acquisition Phase(Single Ended)

When the ADC starts a conversion (Figure 5), SW2 will open and SW1 will move to position B, causing the comparator to become unbalanced. The control logic and the charge redistribution DAC is used to add and subtract fixed amounts of charge from the sampling capacitor arrays to bring the comparator back into a balanced condition. When the comparator is rebalanced, the conversion is complete. The Control Logic generates the ADC output code

set. When operating in Sequence mode the output coding for each channel in the sequence will be the value written to the coding bit during the last write to the Control Register.

Transfer Functi o n s The designed code transitions occur at successive integer LSB values (i.e., 1 LSB, 2 LSB, and so on). The LSB size is dependant on the Analog input Range selected.

Table 6. LSB sizes for each Analog Input Range

Input Range Full Scale Range/8192 LSB Size

±10V 20V/8192 2.441 mV

±5V 10V/8192 1.22 mV

±2.5V 5V/8192 0.61 mV

0 to 10V 10V/8192 1.22 mV

CAPACITIVE

DAC

CONTROL

LOGIC

Vin0

AGND

SW1

COMPARATOR

SW2

Figure 5. ADC Conversion Phase(Single Ended)

Figure 6 shows the differential configuration during the Acquisition phase. For the Conversion Phase, SW3 will open, SW1 and SW2 will move to position B, see Figure 7. The output impedances of the source driving the Vin+ and Vin- pins must be matched; otherwise the two inputs will have different settling times, resulting in errors.

CAPACITIVE

COMPARATOR

SW3

Vin+

Vin-

SW1

SW2

REF

Figure 6. ADC Differential Configuration during Acquisition Phase

COMPARATOR

SW3

Vin+

Vin-

SW1

SW2

REF

Figure 7. ADC Differential Configuration during Conversion Phase

DAC

CONTROL

LOGIC

CAPACITIVE

DAC

CAPACITIVE

DAC

CONTROL

LOGIC

CAPACITIVE

DAC

The ideal transfer characteristic for the AD7323 when Twos Complement coding is selected is shown in Figure 8, and the ideal transfer characteristic for the AD7323 when Straight Binary coding is selected is shown in Figure 9.

Figure 8 Twos Complement Transfer Characteristic (Bipolar Ranges)

Output Coding The AD7323 default output coding is set to two’s complement. The output coding is controlled by the Coding bit in the Control Register. To change the output coding to Straight Binary Coding the Coding bit in the Control Register must be

Rev. PrA| Page 10 of 22

Figure 9. Straight Binary Transfer Characteristic (Bipolar Ranges)

Preliminary Technical Data AD7323

ANALOG INPUT

The analog inputs of the AD7323 may be configured as SingleEnded, True differential or Pseudo Differential via the Control Register Mode Bits as shown Table 9 of the Register Section. The AD7323 can accept True bipolar input signals. On power up the Analog inputs will operate as 4 Single-Ended Analog Input Channels. If True Differential or Pseudo Differential is required, a write to the Control register is necessary to change this configuration after power up.

Figure 10 shows the equivalent Analog input circuit of the AD7323 in Single-Ended Mode. Figure 11 shows the equivalent Analog input structure in Differential mode. The Two Diodes provide ESD protection for the Analog Inputs.

Vin0

Figure 10. Equivalent Analog Input Circuit-(Single Ended)

Vin+

Vin-

Figure 11. Equivalent Analog Input Circuit-(Differential)

C2R1

Care should be taken to ensure the Analog Input never exceeds the V

and VSS supply rails by more than 300 mV. This will

cause the diodes to become forward biased and start conducting into either the V

or VSS rails. These diodes can

conduct up to 10 mA without causing irreversible damage to the part.

The Capacitor C1, in Figure 10 and Figure 11 is typically 4 pF and can primarily be attributed to pin capacitance. The resistor R1, is a lumped component made up of the on-resistance of the input multiplexer and the track-and-hold switch. The Capacitor C2, is the sampling capacitor, its capacitance will vary depending on the Analog input range selected.

the Track-and-Hold is greater than the Nyquist rate of the ADC, the AD7323 can handle frequencies up to 7 MHz.

The Track-and-Hold enters its tracking mode on the 14

rising edge after the

falling edge. The time required to

SCLK

acquire an input signal will depend on how quickly the sampling capacitor is charged. With zero source impedance 200 ns will be sufficient to acquire the signal to the 13-Bit level.

The acquisition time required is calculated using the following formula:

= 10 x ((R

ACQ

SOURCE

+ R) C)

where C is the Sampling Capacitance and R is the resistance seen by the track-and-hold amplifier looking back on the input. For the AD7323, the value of R will include the on-resistance of the input multiplexer. The value of R is typically 300 Ω. R

SOURCE

should include any extra source impedance on the Analog input.

The AD7323 enters track on the 14th SCLK rising edge. When running the AD7323 at a throughput rate of 500 kSPS with a 10 MHz SCLK signal the ADC will have approx. 1.5 SCLK periods

plus the quiet time, T

plus t

input signal. The ADC goes back into hold on the

, in order to acquire the analog

QUIET

falling

edge.

TYPICAL CONNECTION DIAGRAM

Figure 12 shows a typical connection diagram for the AD7323. In this configuration the AGND pin is connected to the Analog ground plane of the system. The DGND pin is connected to the Digital ground plane of the system. The Analog Inputs on the AD7323 can be configured to operate in Single Ended, True Differential or Pseudo Differential Mode. The AD7323 can operate with either the internal or an external reference. In Figure 12, the AD7323 is configured to operate with the internal

2.5V reference. A 470 nF decoupling capacitor is required when operating with the internal reference.

The V voltage. The V voltage analog input structures. The voltage on these pins must be equal to or greater than the highest analog input range selected on the analog input channels, see Table 5 for more information. The V of the microprocessor. The voltage applied to the V controls the voltage of the serial interface.

pin can be connected to either a 3V or a 5V supply

and VSS are the dual supplies for the high

pin is connected to the supply voltage

DRIVE

input

Track-and-Hold Section

The Track-and-Hold on the Analog Input of the AD7323 allows the ADC to accurately convert an input sine wave of full scale amplitude to 12-Bit Plus Sign accuracy. The input bandwidth of

Rev. PrA| Page 11 of 22

AD7323 Preliminary Technical Data

Figure 12. Typical Connection Diagram

Rev. PrA| Page 12 of 22

AD7323 Preliminary Technical Data

AD7323 Registers

The AD7323 has three-programmable registers, the Control Register, Sequence Register, and t he Range Register. These registers are write only registers.

Addressing these Registers

A serial transfer on the AD7323 consists of 16 SCLK cycles. The three MSBs on the DIN line during this 16 SCLK transfer are decoded to determine which register is addressed during the serial transfer. The three MSBs consists of the Write bit, Register Select 1 bit and Register Select 2 bit. The Register Select bits are used to determine which of the four on-board registers is selected. The Write bit will determine if the Data on the DIN line following the Register select bits will be loaded into the addressed register or not. If the Write bit is 1 the bits will be loaded into the register addressed by the Register Select bits. If the Write Bit is a 0 the data on the DIN will not be loaded into any register.

Table 7. Decoding Register Select bits and Write bit.

Wr it e Register Select1 Register Select2 Comment

0 0 0 Data on the DIN line during this serial transfer will be ignored

1 0 0 This combination selects the Control Register. The subsequent 12 bits will be loaded

into the Control Register.

1 0 1 This combination selects the Range Register. The subsequent 8 bits will be loaded

into the Range Register.

1 1 1 This combination selects the Sequence Register. The subsequent 8 bits will be

loaded into the Sequence Register.

CONTROL REGISTER

The Control Register is used to select the Analog Input configuration, Reference, Coding, Power mode etc. The Control Register is a write only 12-bit register. Data loaded on the DIN line corresponds to the AD7323 configuration for the next conversion. Data should be loaded into the Control Register after the Range Register and the Sequence Register has been initialized, that is if the Sequence register is being used. The bit functions of the Control Register are outlined in Table 8.

Rev. PrA | Page 13 of 22

AD7323 Preliminary Technical Data

Control Register (The Power-up status of all bits is 0)

Table 8. Control Register

MSB LSB

Write

Bit Mnemonic Comment

12 DONTC

11,10 ADD1, ADD0

9, 8

7,6 PM1, PM0 Power Management Bits. These two bits are used to select different power mode options.See Table 10. 5 Coding

4 Ref

3,2 Seq1/Seq2 The Sequence 1 and Sequence 2 bits are used to control the operation of the Sequencer. See

1 ZERO A zero must be written to this bit to ensure correct operation of the AD7323.

Mode1, Mode0

DONTC ADD1 ADD0 Mode1 Mode0 PM1 PM0 Coding Ref Seq1 Seq2 ZERO

Don’t Care. The value written to this bit of the Control Register is a don’t care, i.e., it doesn’t matter if the bit is 0 or 1.

These two Channel Address bits are used to select the analog input channel for the next conversion if the Sequencer is not being used. If the Sequencer is being used, these two Channel Address bits are used to select the final channel in a consecutive sequence.

These two mode bits are used to select the configuation on the four Analog Input Pins. They are used in conjunction with the channel Address bits. On the AD7323 the analog inputs can be configured as either 4 Single Ended Inputs, 2 Fully Differential Inputs, 2 Pseudo Differential inputs or 3 Pseudo Differential Inputs. See Table 9

This bit is used to select the type of output coding the AD7323 will use for the next conversion result. If the Coding = 0 then the output coding will be 2s Complement. If Coding = 1, then the output coding will be Straight Binary. When operating in Sequence mode the output coding for each channel will be the value written to the coding bit during the last write to the Control Register.

Reference bit. This bit is used to enable or disable the internal reference. If this Ref = 0 then the External Reference will be enabled and used for the next conversion and the internal reference will be disabled. If ref = 1 then the Internal Reference will be used for the next conversion. When operating in Sequence mode the Reference used for each channel will be the value written to the Ref bit during the last write to the Control Register.

Table 11.

Table 9. Analog Input Configuration Selection

Mode1 =1, Mode0 = 1 Mode1 = 1, Mode0 =0 Mode1 = 0, Mode0 =1 Mode1 =0, Mode0 =0 Channel Address Bits

3 Pseudo Differential I/ps 4 Fully Differential i/ps 2 Pseudo Differential i/ps Four-Single Ended i/ps

ADD1 ADD0 Vin+ Vin- Vin+ Vin- Vin+ Vin- Vin+ Vin-

0 0 Vin0 Vin3 Vin0 Vin1 Vin0 Vin1 Vin0 AGND 0 1 Vin1 Vin3 Vin0 Vin1 Vin0 Vin1 Vin1 AGND 1 0 Vin2 Vin3 Vin2 Vin3 Vin2 Vin3 Vin2 AGND 1 1 Not Allowed Vin2 Vin3 Vin2 Vin3 Vin3 AGND

Rev. PrA | Page 14 of 22

Preliminary Technical Data AD7323

Table 10. Power Mode Selection

PM1 PM0 Description

1 1

1 0

Full Shutdown Mode, In this mode all internal circuitry on the AD7323 is powered down. Information in the Control register is retained when the AD7323 is in Full Shutdown Mode.

Auto Shutdown Mode, The AD7323 will enter Full Shut down at the end of each conversion when the control register is updated. All internal circuitry is powered down in Full Shutdown.

Auto Standby Mode, In this mode all internal circuitry is powered down excluding the

0 1

internal Reference. The AD7323 will enter Auto Standby Mode at the end of the Conversion after the control register is updated.

0 0 Normal Mode, All internal Circuitry is powered up at all times.

Table 11. Sequencer Selection

Seq1 Seq2 Sequence type

0 0 The Channel Sequencer is not used. The Analog Channel selected by programming the ADD1 and ADD0 bits in

the Control Register selects the next channel for conversion.

0 1 This selects the Sequence of Channels as previously programmed in the Sequence register for conversion. The

AD7323 will start converting on the lowest channel in the sequence. It converts the channels in ascending

order. If uninterrupted the AD7323 will keep converting the sequence. The range for each channel selected will

default to the Ranges previously written into the Range Registers.

1 0 This Configuration is used in conjunction with the Channel Address Bits in the Control Register. It allows

continuous conversions on a consecutive sequence of channels, from channel 0, up to and including, a final

channel selected by the Channel Address Bits in the control register. The range for each channel will default to

the Ranges previously written into the Range Registers.

1 1 The Channel Sequencer is not used. The Analog Channel selected by programming the ADD1 and ADD0 bits in

the Control Register selects the next channel for conversion.

THE SEQUENCE REGISTER

The Sequence Register on the AD7323 is a 4-Bit Write only register. Each of the four Analog input channels has one corresponding bit in the Sequence Register. To select a channel for inclusion in the sequence set the corresponding channel bit to 1 in the Sequence Register.

Table 12. Sequencer Register

MSB LSB

Write Register Select 1 Register Select 2 Vin0 Vin1 Vin2 Vin3 0 0 0 0 0 0 0 0 0

RANGE REGISTER

The Range register to used to select one Analog input Range per Analog input channel. Range. It is an 8-Bit write only Register, wit h two dedicated Range bits for each of the Analog Input Channels from Channel 0 to Channel3 . There are four Analog input Ranges to choose from, ±10V, ±5V, ±2.5V, 0 to 10V. A write to the Range Register is selected by setting the Write bit to 1 and the Register Select bits to 0, 1. Once the initial write to the Range Register occurs the AD7323 automatically configures the Analog inputs from Channel 0 to Channel 3 to the appropriate range, as indicated by the Range register, each time any one of these analog input channels is selected. The ±10V input Range is selected by default on each analog input channel. See Table 13.

Rev. PrA| Page 15 of 22

AD7323 Preliminary Technical Data

Table 13. Range Register

MSB LSB Write Reg Select 1 Reg Select2 Vin0A Vin0B Vin1A Vin1B Vin2A Vin2B Vin3A Vin3B 0 0 0 0 0

VinXA VinXB Description

This combination selects the ± 10V Input Range on Analog Input X.

0 1 This combination selects the ±5V Input

Range on Analog Input X.

1 0 This combination selects the ± 2.5V

Input Range on Analog Input X.

1 1 This combination selects the 0 to 10V

Input Range on Analog Input X.

Rev. PrA| Page 16 of 22

AD7323 Preliminary Technical Data

SEQUENCER OPERATION

POWER ON

DIN:- WRITE TO RANGE REGISTER TO SELECT THE RANGE FOR EACH ANALOG

INPUT CHANNEL

DOUT:- CONVERSION RESULT FROM CHANNEL O, ± 10V RANGE, SINGLE-ENDED MODE.

DIN:- WRITE TO SEQUENCE REGISTER TO SELECT THE ANALOG INPUT CHANNELS

TO BE INCLUDED IN THE SEQUENCE

DOUT:- CONVERSION RESULT FROM CHANNEL O, SINGLE-ENDED MODE, RANGE

SELECTED IN RANGE REGISTER

DIN:- WRITE TO CONTROL REGISTER TO START THE SEQUENCE, SEQ1 = 0, SEQ2 = 1.

DOUT:- CONVERSION RESULT FROM CHANNEL O, SINGLE-ENDED MODE, RANGE SELECT-

ED IN RANGE REGISTER

DIN:- WRITE TO CONTROL REGISTER TO

STOP THE SEQUENCE, SEQ1 = 0, SEQ2

= 0.

DOUT:- CONVERSION RESULT FROM

CHANNEL IN SEQUENCE

DIN:- TIE DIN LOW/WRIT E BIT = 0 TO CONTINUE TO CONVERT THROUGH THE

SEQUENCE OF CHANNELS

DOUT:- CONVERSION RESULT FROM FIRST CHANNEL IN THE SEQUENCE

STOPPING A

SEQUENCE

SELECTING A NEW SEQUENCE

DIN:- WRITE TO SEQUENCE REGISTER TO SELECT THE NEW SEQUENCE

DOUT:- CONVERSION RESULT FROM CHANNEL IN THE FIRST SEQUENCE

Figure 13. Programmable sequence Flow Chart

The AD7323 can be configured to automatically cycle through a number of selected channels using the on-chip sequence register and the SEQ1 and SEQ2 bits in the control register. Figure 13 shows how to program the AD7323 register in order to operate in sequence mode.

After power up all of the three on-chip registers will contain default values. Each analog input will have a default input range of ± 10V. If different Analog input ranges are required then a write to the range register is required, this is shown in the first serial transfer in Figure 13. This initial serial transfer is only necessary if Input ranges other than the default Ranges are required. After the Analog Input ranges are configured a write to the Sequence register is necessary to select the channels to be included in the sequence. Once the channels for the sequence have been selected, the sequence can be initiated by writing to the control register and setting the SEQ1 =0, SEQ2 = 1. The AD7323 will continue to convert through the selected sequence uninterrupted provided the Sequence Register remains unchanged and SEQ1 = 0 and SEQ2 = 1 in the Control Register.

DIN TIED LOW/WRITE BIT = 0

CONTINUOUSLY CON-

VERT ON THE SELECT-

ED SEQUENCE OF

CHANNELS

If during a sequence a change to one of the range registers is required, it is first necessary to stop the sequence by writing to the Control Register and setting SEQ1 = 0 and SEQ2 = 0. Next the write to the range register can be completed to change the required range. Then the previously selected sequence can be initiated again by writing to the Control Register and setting SEQ1 = 0 and SEQ2 = 1, the ADC will then convert on the first channel in the sequence.

The AD7323 can be configured to convert a sequence of consecutive channels, See Figure 14. This sequence will begin by converting on channel 0 and end with a final channel as selected by bits ADD1 to ADD0 in the Control Register. In this configuration there is no need for a write to the Sequence register. To operate the AD7323 in this mode set SEQ1 = 1 and SEQ2 = 0 and select the final channel in the sequence by programming bits ADD1 to ADD0 in the Control Register. Once the control register is configured to operate the AD7323 in this mode the DIN line can be held low or the WRITE bit can be set to 0, the AD7323 will then continue operating in this

Rev. PrA | Page 17 of 22

AD7323 Preliminary Technical Data

mode. To return to traditional multichannel operation a write to the Control Register is necessary, setting SEQ1 = 0 and SEQ2 =0.

When the SEQ1 and SEQ2 are both set to 0 or when both are set to 1 the AD7323 is configured to operate in traditional Multichannel mode where a write to the channel Address bits, ADD1 to ADD0, in the Control Register selects the next channel for conversion. In traditional multichannel mode it is

POWER ON

DIN:- WRITE TO RANGE REGISTER TO SELECT THE RANGE FOR ANALOG INPUT

CHANNELS

DOUT:- CONVERSION RESULT FROM CHANNEL O, ± 10V RANGE, SINGLE-ENDED MODE.

DIN:- WRITE TO CONTROL REGISTER TO SELECT THE FINAL CHANNEL IN THE CON-

SECUTIVE SEQUENCE, SET SEQ1 = 1 AND SEQ2 = 0. SELECT OUTPUT CODING FOR

SEQUENCE.

DOUT;- CONVERSION RESULT FROM CHANNEL 0, RANGE SELECTED IN RANGE

REG, SINGLE-ENDED MODE.

necessary to write to the AD7323 in each serial transfer to select the next channel for conversion. However if a number of conversions are required on one channel then one write to the control register is necessary to select this channel via the channel address bits, ADD1, ADD0. The DIN line c an t hen be held low or the write bit set to zero during the require number of conversions.

DIN:- WRITE BIT = 0 OR DIN LINE HELD LOW TO CONTINUE THROUGH SEQUENCE

OF CONSECUTIVE CHANNELS

DOUT;- CONVERSION RESULT FROM CHANNEL 0, RANGE SELECTED IN RANGE

REG, SINGLE-ENDED MODE.

DIN:- WRITE BIT = 0 OR DIN LINE HELD LOW TO CONTINUE THROUGH SEQUENCE

OF CONSECUTIVE CHANNELS

DOUT;- CONVERSION RESULT FROM CHANNEL 1, RANGE SELECTED IN RANGE

REG, SINGLE-ENDED MODE.

STOPPING A

SEQUENCE

DIN:- WRITE TO CONTROL REGISTER TO

STOP THE SEQUENCE, SEQ1 = 0, SEQ2

= 0.

DOUT:- CONVERSION RESULT FROM

CHANNEL IN SEQUENCE

Figure 14. Flow Chart for Consecutive Sequence of Channels

CONTINUOUSLY CON-

VERT ON CONSECU-

TIVE SEQUENCE OF

CHANNELS

DIN TIED LOW/WRITE BIT = 0

Rev. PrA| Page 18 of 22

Preliminary Technical Data AD7323

REFERENCE

The AD7323 can operate with either the internal 2.5V on-chip reference or an externally applied reference. The internal reference is selected by setting the REF bit in the Control Register to 1. On power up the REF bit will be 0, selecting the external Reference for the AD7323 conversion. For external reference operation the REF

/REF

to AGND with a 470 nF capacitor.

The internal Reference circuitry consists of a 2.5V band gap reference and a reference buffer. When operating the AD7323 in internal Reference mode the 2.5V internal reference is available at the REF

/REF

pin. When using the AD7323 with the

OUT

internal reference the REFIN/REFOUT pin should be decoupled to AGND using a 470 nF cap. It is recommended that the Internal Reference be buffered before applying it else where in the system.

The AD7323 is specified for a 2.5V to 3V reference range. When a 3V reference is selected the ranges will be, ±12V, ±6V, ±3V and 0 to 12V. For these ranges the V equal to or greater than the max Analog Input Range selected.

pin should be decoupled

OUT

and VSS supply must be

On power up if the internal reference operation is required for the ADC conversion, a write to the control register is necessary to set the REF bit to 1. During the Control Register write the conversion result from the first initial conversion will be invalid. The reference buffer will require TBD µs to power up and charge the 470 nF decoupling cap, during the power up time the conversion result from the ADC will be invalid.

Rev. PrA| Page 19 of 22

AD7323 Preliminary Technical Data

If a write to the control register occurs while the part is in Full

MODES OF OPERATION

The AD7323 has a number of different modes of operation. These modes are designed to provide flexible power management options. These options can be chosen to optimize the power dissipation/throughput rate ratio for the differing application requirements. The mode of operation of the AD7323 is controlled by the Power Management bits, PM1 and PM0, in the Control register as detailed in Table 10.The default mode is Normal Mode, where all internal circuitry is fully powered up.

Normal Mode (PM1 = PM0 = 0)

This mode is intended for the fastest throughput rate performance, the AD7323 is fully powered up at all times. Figure 15 shows the general diagram of operation of the AD7323 in Normal Mode.

The Conversion is initiated on the falling edge of track and hold will enter hold mode as described in the Serial Interface Section. The Data on the DIN line during the 16 SCLK transfer will be loaded into one of the on-chip registers, provided the Write bit is set. The register is selected by programming the Register select bits, see Table 7 of the Register section.

and the

Shut down mode, with the power management bits, PM1 and PM0 set to 0, normal mode, the part will begin to power up on

rising edge.

the

To ensure the AD7323 is fully powered up, t

elapse before the next

falling edge.

POWER UP

, shoul d

Auto Shutdown Mode (PM1 = 1, PM0 = 0)

Once the Auto Shutdown mode is selected the AD7323 will automatically enter shutdown at the end of each conversion. The AD7323 retains information in the registers during Shutdown. The track-and-hold is in hold during shutdown. On

the falling

edge, the track-and-hold that was in hold during

shutdown will return to track.

The power-up from Auto Shutdown is TBD µs

In this mode the power consumption of the AD7323 is greatly reduced with the part entering shutdown at the end of each conversion. When the control registers is programmed to move into Auto Shutdown mode, it does so at the end of the conversion.

Auto Standby Mode (PM1 = 0, PM0 =1)

In Auto Standby mode portions of the AD7323 are powered down but the on-chip reference remains powered up. The reference bit in the Control register should be 0 to ensure the on-chip reference is enabled. This mode is similar to Auto Shutdown but allows the AD7323 to power up much faster, allowing faster throughput rates to be achieved.

Figure 15. Normal Mode

The AD7323 will remain fully powered up at the end of the conversion provided both PM1 and PM0 contain 0 in the control Register.

Sixteen serial clock cycles are required to complete the conversion and access the conversion result. At the end of the

conversion

may idle high until the next conversion or may

idle low until sometime prior to the next conversion.

Once the data transfer is complete, another conversion can be initiated after the quiet time, t

, has elapsed.

QUIET

Full Shutdown Mode (PM1 = PM0 = 1)

In this mode all internal circuitry on the AD7323 is powered down. The part retains information in the Registers during Full Shut down. The AD7323 remains in Full shutdown mode until the power managements bits in the Control Register, PM1 and PM0, are changed.

Rev. PrA | Page 20 of 22

The AD7323 will enter standby at the end of the conversion. The part retains information in the Registers during Standby.

The AD7323 will remain in standby until it receives a edge. The ADC will begin to power up on the On this

falling edge the track-and-hold that was in hold

falling

falling edge.

mode while the part was in Standby will return to track. Wakeup time from Standby is 1 µs. The user should ensure that 1 µs has elapsed before attempting a valid conversion. When running the AD7323 with the maximum 10 MHz SCLK, one dummy conversion of 16 x SCLKs is sufficient to power up the ADC. This dummy conversion effectively halves the throughput rate of the AD7323, with every second conversion result being a valid result. Once Auto Standby mode is selected, the ADC can

move in and out of the low power state by controlling the signal.

AD7323 Preliminary Technical Data

SERIAL INTERFACE

Figure 16 shows the timing diagram for the serial interface of the AD7323. The serial clock applied to the SCLK pin provides the conversion clock and also controls the transfer of information to and from the AD7323 during a conversion.

The

signal initiates the data transfer and the conversion process. The falling edge of hold mode, take the bus out of three-state and the analog input signal is sampled at this point. Once the conversion is initiated it will require 16 SCLK cycles to complete.

The track-and-hold will go back into track on the 14th SCLK rising edge. On the sixteenth SCLK falling edge, the DOUT line will return to three-state. If the rising edge of 16 SCLK cycles have elapsed, the conversion will be terminated,

puts the track-and-hold into

occurs before

the DOUT line will return to three-state, and depending on when the

signal is brought high the addressed register may or may not be updated. Data is clocked into the AD7323 on the SCLK falling edge. The three MSB on the DIN line are decoded to select which register is being addressed. The Control Register is an eleven bit register, if the control register is addressed by the three MSB, the data on the DIN line will be loaded into the

Control on the 15

SCLK falling edge. If the Sequence register

or the Range register is addressed the data on the DIN line will

be loaded into the addressed register on the 11

SCLK falling

edge.

Conversion data is clocked out of the AD7323 on each SCLK falling edge. Data on the DOUT line will consist of two leading zeros, two channel identifier bits and the 12-Bit Plus Sign conversion result. The channel identifier bits are used to indicate which channel the conversion result corresponds to.

+5

SCLK

DOUT

DIN

3-STATE

ZERO

WRITE

ADD1

2 ID BITS

Reg Sel1

ADD0

Reg Sel2

SIGN

MSB

DB11

convert

DB10

Figure 16. Serial Interface timing Diagram (Control register write)

DB2

DB1

LSB

DB0

3-STATE

DONTC

Rev. PrA | Page 21 of 22

AD7323 Preliminary Technical Data

PR05400-0-2/05(PrA)

OUTLINE DIMENSIONS

16-Lead Thin Shrink Small Outline (TSSOP)

(RU-16)

Ordering Guide

AD7323 Products Temperature Package Package Description Package Outline

AD7323BRUZ –40°C to +85°C TSSOP RU-16 EVAL-AD7323CB EVAL-CONTROL BRD2

NOTES 1 This can be used as a stand-alone evaluation board or in conjunction with the EVAL-CONTROL Board for evaluation/demonstration purposes. 2 This board is a complete unit allowing a PC to control and communicate with all Analog Devices evaluation boards ending in the CB designators. To order a complete

evaluation kit, the particular ADC evaluation board, e.g., EVAL-AD7323CB, the EVAL-CONTROL BRD2, and a 12V transformer must be ordered. See relevant Evaluation Board Technical note for more information.

Evaluation Board Controller Board

ESD CAUTION

ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although this product features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality.

Rev. PrA | Page 22 of 22

Datasheet AD7323 Datasheet (Analog Devices)

Specifications and Main Features

Frequently Asked Questions

User Manual