ANALOG DEVICES AD7671 Service Manual

a

DGNDDVD DAV DD AGND REF REFGND

SWITCHED

CAP DAC

CNVSTIMPULSEWARP

OGND

16

CONTROL LOGIC AND

CALIBRATION CIRCUITRY

CLOCK

IND(4R)

4R

OVD D

AD7671

INGND

PD

RESET

BYTESWAP

SER/PAR

D[15:0]

BUSY

CS

RD

OB/2C

SERIAL

PORT

PARALLEL

INTERFACE

INA(R)

R

INC(4R)

4R

INB(2R)

2R

16-Bit, 1 MSPS CMOS ADC

FEATURES
Throughput

1 MSPS (Warp Mode)

800 kSPS (Normal Mode)
INL: 2.5 LSB Max (0.0038% of Full Scale)
16-Bit Resolution with No Missing Codes
S/(N+D): 90 dB Typ @ 250 kHz
THD: –100 dB Typ @ 250 kHz
Analog Input Voltage Ranges

Bipolar: 10 V, 5 V, 2.5 V

Unipolar: 0 V to 10 V, 0 V to 5 V, 0 V to 2.5 V
Both AC and DC Specifications
No Pipeline Delay
Parallel (8/16 Bits) and Serial 5 V/3 V Interface

®

/QSPI™/MICROWIRE™/DSP Compatible

SPI
Single 5 V Supply Operation
Power Dissipation

112 mW Typical

15 W @ 100 SPS
Power-Down Mode: 7 W Max
Package: 48-Lead Quad Flatpack (LQFP)
Package: 48-Lead Chip Scale (LFCSP)
Pin-to-Pin Compatible Upgrade of the AD7665/AD7664

APPLICATIONS
Data Acquisition
Communication
Instrumentation
Spectrum Analysis
Medical Instruments
Process Control

AD7671

*

FUNCTIONAL BLOCK DIAGRAM

PulSAR Selection

Type/kSPS 100–250 500–570 800–1000

Pseudo AD7660 AD7650
Differential AD7664

True Bipolar AD7663 AD7665 AD7671

True Differential AD7675 AD7676 AD7677

18-Bit AD7678 AD7679 AD7674

Simultaneous/ AD7654 AD7655
Multichannel

GENERAL DESCRIPTION

The AD7671 is a 16-bit, 1 MSPS, charge redistribution SAR,
analog-to-digital converter that operates from a single 5 V power
supply. It contains a high speed 16-bit sampling ADC, a resistor
input scaler that allows various input ranges, an internal
conversion clock, error correction circuits, and both serial
and parallel system interface ports.

The AD7671 is hardware factory-calibrated and is comprehen­sively tested to ensure such ac parameters as signal-to-noise ratio
(SNR) and total harmonic distortion (THD), in addition to the
more traditional dc parameters of gain, offset, and linearity.

It features a very high sampling rate mode (Warp), a fast mode
(Normal) for asynchronous conversion rate applications,
low power applications, a reduced power mode (Impulse)
the power is scaled with the throughput.

*Patent pending

REV. B

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. 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.

and, for

where

It is fabricated using Analog Devices’ high performance, 0.6 micron
CMOS process and is available in a 48-lead LQFP and a tiny
48-lead LFCSP, with operation specified from –40∞C to +85∞C.

PRODUCT HIGHLIGHTS

1. Fast Throughput
The AD7671 is a very high speed (1 MSPS in Warp Mode
and 800 kSPS in Normal Mode), charge redistribution, 16-bit
SAR ADC.

2. Single-Supply Operation
The AD7671 operates from a single 5 V supply, dissipates
only 112 mW typical, even lower when a reduced throughput
is used with the reduced power mode (Impulse) and a power­down mode.

3. Superior INL
The AD7671 has a maximum integral nonlinearity of 2.5 LSB
with no missing 16-bit code.

4. Serial or Parallel Interface
Versatile parallel (8 bits or 16 bits) or 2-wire serial interface
arrangement compatible with both 3 V or 5 V logic.

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: [phone] www.analog.com
Fax: [phone] © 2003 Analog Devices, Inc. All rights reserved.

AD7671–SPECIFICATIONS

(–40C to +85C, AVDD = DVDD = 5 V, OVDD = 2.7 V to 5.25 V, unless otherwise noted.)

Parameter Conditions Min Typ Max Unit

RESOLUTION 16 Bits

ANALOG INPUT

Voltage Range V
Common-Mode Input Voltage V
Analog Input CMRR f

– V

IND

INGND

INGND

= 100 kHz 74 dB

IN

± 4 REF, 0 V to 4 REF, ± 2 REF (See Table I)
–0.1 +0.5 V

Input Impedance See Table I

THROUGHPUT SPEED

Complete Cycle In Warp Mode 1 ms
Throughput Rate In Warp Mode 1 1000 kSPS
Time between Conversions In Warp Mode 1 ms
Complete Cycle In Normal Mode 1.25 ms
Throughput Rate In Normal Mode 0 800 kSPS
Complete Cycle In Impulse Mode 1.5 ms
Throughput Rate In Impulse Mode 0 666 kSPS

DC ACCURACY

Integral Linearity Error –2.5 +2.5 LSB

1

No Missing Codes 16 Bits
Transition Noise 0.7 LSB
Bipolar Zero Error

2

, T

MIN

to T

MAX

± 5 V Range, Normal or –45 +45 LSB
Impulse Modes

2

Bipolar Full-Scale Error
Unipolar Zero Error

2

, T

, T

MIN

Unipolar Full-Scale Error

2

, T

MIN

to T

MIN

to T

MAX

to T

MAX

Other Range or Mode –0.1 +0.1 % of FSR

–0.38 +0.38 % of FSR
–0.18 +0.18 % of FSR

MAX

–0.76 +0.76 % of FSR

Power Supply Sensitivity AVDD = 5 V ± 5% ± 9.5 LSB

AC ACCURACY

Signal-to-Noise fIN = 20 kHz 89 90 dB

3

fIN = 250 kHz 90 dB
Spurious-Free Dynamic Range f
Total Harmonic Distortion f

Signal-to-(Noise+Distortion) f

= 250 kHz 100 dB

IN

= 20 kHz –100 –96 dB

IN

= 250 kHz –100 dB

f

IN

= 20 kHz 88.5 90 dB

IN

= 250 kHz, –60 dB Input 30 dB

f

IN

–3 dB Input Bandwidth 9.6 MHz

SAMPLING DYNAMICS

Aperture Delay 2ns
Aperture Jitter 5 ps rms
Transient Response Full-Scale Step 250 ns

REFERENCE

External Reference Voltage Range 2.3 2.5 AVDD – 1.85 V
External Reference Current Drain 1 MSPS Throughput 200 mA

DIGITAL INPUTS

Logic Levels

V

IL

V

IH

I

IL

I

IH

–0.3 +0.8 V
+2.0 DVDD + 0.3 V

–1+1mA
–1+1mA

DIGITAL OUTPUTS

Data Format Parallel or Serial 16-Bit
Pipeline Delay Conversion Results Available Immediately

after Completed Conversion

I

V

OL

V

OH

= 1.6 mA 0.4 V

SINK

I

= –570 mA OVDD – 0.6 V

SOURCE

–2–

REV. B

AD7671

Parameter Conditions Min Typ Max Unit

POWER SUPPLIES

Specified Performance

AVDD 4.75 5 5.25 V
DVDD 4.75 5 5.25 V
OVDD 2.7 5.25

Operating Current

AVDD 15 mA

6

DVDD

6

OVDD

Power Dissipation

In Power-Down Mode

TEMPERATURE RANGE

Specified Performance T

NOTES

1

LSB means least significant bit. With the ± 5 V input range, one LSB is 152.588 mV.

2

See Definition of Specifications section. These specifications do not include the error contribution from the external reference.

3

All specifications in dB are referred to a full-scale input FS. Tested with an input signal at 0.5 dB below full scale, unless otherwise specified.

4

The max should be the minimum of 5.25 V and DVDD + 0.3 V.

5

In Warp Mode.

6

Tested in Parallel Reading Mode.

7

Tested with the 0 V to 5 V range and VIN – V

8

In Impulse Mode.

9

With OVDD below DVDD + 0.3 V and all digital inputs forced to DVDD or DGND, respectively.

10

Contact factory for extended temperature range.

Specifications subject to change without notice.

5

6, 7

1 MSPS Throughput

7.2 mA
37 mA

666 kSPS Throughput
100 SPS Throughput

9

10

1 MSPS Throughput

to T

MIN

= 0 V. See Power Dissipation section.

INGND

MAX

8

8

5

84 95 mW
15 mW
112 125 mW

–40 +85 ∞C

4

V

7 mW

Table I. Analog Input Configuration

Input Voltage Input
Range IND(4R) INC(4R) INB(2R) INA(R) Impedance

± 4 REF
± 2 REF V
± REF V

0 V to 4 REF V
0 V to 2 REF V
0 V to REF V

NOTES

1

2

3

TIMING SPECIFICATIONS

Parameter

2

Typical analog input impedance.
With REF = 3 V, in this range, the input should be limited to –11 V to +12 V.
For this range the input is high impedance.

V

IN

IN

IN

IN

IN

IN

INGND INGND REF 1.63 kW
V

IN

V

IN

V

IN

V

IN

V

IN

(–40C to +85C, AVDD = DVDD = 5 V, OVDD = 2.7 V to 5.25 V, unless otherwise noted.)

INGND REF 948 W
V

IN

REF 711 W

INGND INGND 948 W
V

IN

V

IN

INGND 711 W
V

IN

Note 3

Symbol Min Typ Max Unit

Refer to Figures 11 and 12

Convert Pulsewidth t
Time between Conversions t

1

2

5ns
1/1.25/1.5 Note 1 ms

(Warp Mode/Normal Mode/Impulse Mode)

CNVST LOW to BUSY HIGH Delay t
BUSY HIGH All Modes Except in Master Serial Read after t

3

4

30 ns

0.75/1/1.25 ms

Convert Mode (Warp Mode/Normal Mode/Impulse Mode)
Aperture Delay t
End of Conversion to BUSY LOW Delay t
Conversion Time (Warp Mode/Normal Mode/Impulse Mode) t
Acquisition Time t
RESET Pulsewidth t

5

6

7

8

9

10 ns

250 ns
10 ns

2ns

0.75/1/1.25 ms

1

REV. B

–3–

AD7671

TIMING SPECIFICATIONS

Parameter

(continued)

Symbol Min Typ Max Unit

Refer to Figures 13, 14, 15, and 16 (Parallel Interface Modes)

CNVST LOW to DATA Valid Delay t

10

(Warp Mode/Normal Mode/Impulse Mode)
DATA Valid to BUSY LOW Delay t
Bus Access Request to DATA Valid t
Bus Relinquish Time t

Refer to Figures 17 and 18 (Master Serial Interface Modes)

2

CS LOW to SYNC Valid Delay t
CS LOW to Internal SCLK Valid Delay t
CS LOW to SDOUT Delay t
CNVST LOW to SYNC Delay (Read during Convert) t

(Warp Mode/Normal Mode/Impulse Mode)
SYNC Asserted to SCLK First Edge Delay
Internal SCLK Period
Internal SCLK HIGH
Internal SCLK LOW
SDOUT Valid Setup Time
SDOUT Valid Hold Time
SCLK Last Edge to SYNC Delay

3

3

3

3

3

3

3

CS HIGH to SYNC HI-Z t
CS HIGH to Internal SCLK HI-Z t
CS HIGH to SDOUT HI-Z t

BUSY HIGH in Master Serial Read after Convert

3

CNVST LOW to SYNC Asserted Delay t

11

12

13

14

15

16

17

t

18

t

19

t

20

t

21

t

22

t

23

t

24

25

26

27

t

28

29

20 ns

515ns

4ns
25 40 ns
15 ns

9.5 ns

4.5 ns
2ns
3

(Warp Mode/Normal Mode/Impulse Mode)

Master Serial Read after Convert
SYNC Deasserted to BUSY LOW Delay t

30

Refer to Figures 19 and 21 (Slave Serial Interface Modes)

External SCLK Setup Time t
External SCLK Active Edge to SDOUT Delay t
SDIN Setup Time t
SDIN Hold Time t
External SCLK Period t
External SCLK HIGH t
External SCLK LOW t

NOTES

1

In Warp Mode only, the maximum time between conversions is 1 ms; otherwise, there is no required maximum time.

2

In serial interface modes, the SYNC, SCLK, and SDOUT timings are defined with a maximum load C

3

In Serial Master Read during Convert Mode. See Table II for Master Read after Convert Mode.

Specifications subject to change without notice.

31

32

33

34

35

36

37

5ns
316ns
5ns
5ns
25 ns
10 ns
10 ns

of 10 pF; otherwise, the load is 60 pF maximum.

L

0.75/1/1.25 ms

40 ns

10 ns
10 ns
10 ns

25/275/525 ns

10 ns
10 ns
10 ns

See Table II ms

0.75/1/1.25 ms

25 ns

Table II. Serial Clock Timings in Master Read after Convert

DIVSCLK[1] 0011
DIVSCLK[0] 0101 Unit

SYNC to SCLK First Edge Delay Minimum t
Internal SCLK Period Minimum t
Internal SCLK Period Maximum t
Internal SCLK HIGH Minimum t
Internal SCLK LOW Minimum t
SDOUT Valid Setup Time Minimum t
SDOUT Valid Hold Time Minimum t
SCLK Last Edge to SYNC Delay Minimum t
BUSY HIGH Width Maximum (Warp) t
BUSY HIGH Width Maximum (Normal) t
BUSY HIGH Width Maximum (Impulse) t

Specifications subject to change without notice.

18

19

19

20

21

22

23

24

28

28

28

4202020 ns
25 50 100 200 ns
40 70 140 280 ns
15 25 50 100 ns
9244999 ns

4.5 22 22 22 ns
243089 ns
360140 300 ns

1.5 2 3 5.25 ms

1.75 2.25 3.25 5.5 ms
2 2.5 3.5 5.75 ms

–4–

REV. B

AD7671

36

35

34

33

32

31

30

29

28

27

26

25

13 14

15 16 17 18

19 20

21 22

23 24

1

2

3

4

5

6

7

8

9

10

11

12

48

47 46

45 44 39 38 3743 42 41 40

PIN 1
IDENTIFIER

TOP VIEW

(Not to Scale)

AGND

CNVST

PD

RESET

CS
RD

DGND

AGND

AV DD

NC

BYTESWAP

OB/2C
WARP

IMPULSE

NC = NO CONNECT

SER/PAR

D0

D1

D2/DIVSCLK[0]

BUSY

D15

D14

D13

AD7671

D3/DIVSCLK[1]

D12

D4/EXT/INT

D5/INVSYNC

D6/INVSCLK

D7/RDC/SDIN

OGND

OVD D

DVD D

DGND

D8/SDOUT

D9/SCLK

D10/SYNC

D11/RDERROR

NCNCNCNCNC

IND(4R)

INC(4R)

INB(2R)

INA(R)

INGND

REFGND

REF

ABSOLUTE MAXIMUM RATINGS

Analog Inputs

2

, INC2, INB2 . . . . . . . . . . . . . . . . . . . . –11 V to +30 V

IND

1

INA, REF, INGND, REFGND, AGND

. . . . . . . . . . . . . . . . . . . . . . . . . . . – 0.3 V to AVDD + 0.3 V

Ground Voltage Differences

AGND, DGND, OGND . . . . . . . . . . . . . . . . . . . . . . ± 0.3 V

Supply Voltages

AVDD, DVDD, OVDD . . . . . . . . . . . . . . . . . –0.3 V to +7 V

AVDD to DVDD,

AVDD to OVDD . . . . . . . . . . . . . . ± 7 V

DVDD to OVDD . . . . . . . . . . . . . . . . . . . . . . –0.3 V to +7 V

Digital Inputs . . . . . . . . . . . . . . . . –0.3 V to DVDD + 0.3 V

Internal Power Dissipation

3

. . . . . . . . . . . . . . . . . . . . 700 mW

Internal Power Dissipation4 . . . . . . . . . . . . . . . . . . . . . . 2.5 W

Junction Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . 150∞C

Storage Temperature Range . . . . . . . . . . . . –65∞C to +150∞C

Lead Temperature Range

(Soldering 10 sec) . . . . . . . . . . . . . . . . . . . . . . . . . . . 300∞C

NOTES

1

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 indicated in the operational section of
this specification is not implied. Exposure to absolute maximum rating conditions
for extended periods may affect device reliability.

2

See Analog Inputs section.

3

Specification is for device in free air: 48-Lead LQFP: qJA = 91∞C/W, qJC = 30∞C/W.

4

Specification is for device in free air: 48-Lead LFCSP: qJA = 26∞C/W.

PIN CONFIGURATION

ST-48 and CP-48

1.6mA

TO OUTPUT

PIN

*IN SERIAL INTERFACE MODES, THE SYNC, SCLK, AND
SDOUT TIMINGS ARE DEFINED WITH A MAXIMUM LOAD

OF 10pF; OTHERWISE, THE LOAD IS 60pF MAXIMUM.

C

L

C

L

60pF

*

500A

Figure 1. Load Circuit for Digital Interface Timing,

I

OL

1.4V

I

OH

0.8V

t

DELAY

0.8V 0.8V

2V

t

DELAY

2V2V

Figure 2. Voltage Reference Levels for Timing

SDOUT, SYNC, SCLK Outputs, CL = 10 pF

ORDERING GUIDE

Model Temperature Range Package Description Package Option

AD7671AST –40∞C to +85∞CQuad Flatpack (LQFP) ST-48
AD7671ASTRL –40∞C to +85∞CQuad Flatpack (LQFP) ST-48
AD7671ACP –40∞C to +85∞CChip Scale (LFCSP) CP-48
AD7671ACPRL –40∞C to +85∞CChip Scale (LFCSP) CP-48
EVAL-AD7671CB
EVAL-CONTROL BRD2

NOTES

1

This board can be used as a standalone evaluation board or in conjunction with the EVAL-CONTROL BRD2 for evaluation/demonstration purposes.

2

This board allows a PC to control and communicate with all Analog Devices evaluation boards ending in the CB designators.

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
the AD7671 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.

1

2

Evaluation Board
Controller Board

REV. B

–5–

AD7671

PIN FUNCTION DESCRIPTION

Pin
No. Mnemonic Type Description

1 AGND P Analog Power Ground Pin.

2 AVDD P Input Analog Power Pin. Nominally 5 V.

3, 44–48 NC No Connect.

4 BYTESWAP Parallel Mode Selection (8-/16-Bit). When LOW, the LSB is output on D[7:0] and the MSB is

output on D[15:8]. When HIGH, the LSB is output on D[15:8] and the MSB is output on D[7:0].

5 OB/2C DI Straight Binary/Binary Twos Complement. When OB/2C is HIGH, the digital output is straight

binary; when LOW, the MSB is inverted, resulting in a twos complement output from its internal
shift register.

6 WARP DI Mode Selection. When HIGH and IMPULSE LOW, this input selects the fastest mode, the maximum

throughput is achievable and a minimum conversion rate must be applied in order to guarantee
full specified accuracy. When LOW, full accuracy is maintained independent of the minimum
conversion rate.

7IMPULSE DI Mode Selection. When HIGH and WARP LOW, this input selects a reduced Power Mode.

In this mode, the power dissipation is approximately proportional to the sampling rate.

8 SER/PAR DI Serial/Parallel Selection Input. When LOW, the Parallel Port is selected; when HIGH, the Serial

Interface Mode is selected and some bits of the data bus are used as a Serial Port.

9, 10 D[0:1] DO Bit 0 and Bit 1 of the Parallel Port Data Output Bus. When SER/PAR is HIGH, these outputs are

in high impedance.

11, 12 D[2:3] or DI/O When SER/PAR is LOW, these outputs are used as Bit 2 and Bit 3 of the Parallel Port Data

Output Bus.

DIVSCLK[0:1] When SER/PAR is HIGH, EXT/INT is LOW and RDC/SDIN is LOW, which is the Serial Master

Read after Convert Mode. These inputs, part of the Serial Port, are used to slow down, if desired,
the internal serial clock that clocks the data output. In the other serial modes, these pins are high
impedance outputs.

13 D[4] DI/O When SER/PAR is LOW, this output is used as Bit 4 of the Parallel Port Data Output Bus.

or EXT/INT When SER/PAR is HIGH, this input, part of the Serial Port, is used as a digital select input for

choosing the internal or an external data clock, called Master and Slave Modes, respectively. With
EXT/INT tied LOW, the internal clock is selected on SCLK output. With EXT/INT set to a logic
HIGH, output data is synchronized to an external clock signal connected to the SCLK input and
the external clock is gated by CS.

14 D[5] DI/O When SER/PAR is LOW, this output is used as Bit 5 of the Parallel Port Data Output Bus.

or INVSYNC When SER/PAR is HIGH, this input, part of the Serial Port, is used to select the active state of

the SYNC signal. When LOW, SYNC is active HIGH. When HIGH, SYNC is active LOW.

15 D[6] DI/O When SER/PAR is LOW, this output is used as Bit 6 of the Parallel Port Data Output Bus.

or INVSCLK When SER/PAR is HIGH, this input, part of the Serial Port, is used to invert the SCLK signal. It is

active in both Master and Slave Mode.

16 D[7] DI/O When SER/PAR is LOW, this output is used as Bit 7 of the Parallel Port Data Output Bus.

or RDC/SDIN When SER/PAR is HIGH, this input, part of the Serial Port, is used as either an external data input

or a read mode selection input, depending on the state of EXT/INT.
When EXT/INT is HIGH, RDC/SDIN could be used as a data input to daisy-chain the conversion

results from two or more ADCs onto a single SDOUT line. The digital data level on SDIN is output
on DATA with a delay of 16 SCLK periods after the initiation of the read sequence.

When EXT/INT is LOW, RDC/SDIN is used to select the Read Mode. When RDC/SDIN is HIGH,
the previous data is output on SDOUT during conversion. When RDC/SDIN is LOW, the data can
be output on SDOUT only when the conversion is complete.

17 OGND P Input/Output Interface Digital Power Ground.

18 OVDD P Input/Output Interface Digital Power. Nominally at the same supply as the supply of the host

interface (5 V or 3 V).

19 DVDD P Digital Power. Nominally at 5 V.

20 DGND P Digital Power Ground.

–6–

REV. B

AD7671

PIN FUNCTION DESCRIPTION (continued)

Pin
No. Mnemonic Type Description

21 D[8] DO When SER/PAR is LOW, this output is used as Bit 8 of the Parallel Port Data Output Bus.

or SDOUT When SER/PAR is HIGH, this output, part of the Serial Port, is used as a serial data output

synchronized to SCLK. Conversion results are stored in an on-chip register. The AD7671 provides
the conversion result, MSB first, from its internal shift register. The data format is determined
by the logic level of OB/2C. In Serial Mode, when EXT/INT is LOW, SDOUT is valid on both
edges of SCLK.

In Serial Mode, when EXT/INT is HIGH:

If INVSCLK is LOW, SDOUT is updated on SCLK rising edge and valid on the next falling edge.

If INVSCLK is HIGH, SDOUT is updated on SCLK falling edge and valid on the next rising edge.

22 D[9] DI/O When SER/PAR is LOW, this output is used as Bit 9 of the Parallel Port Data Output Bus.

or SCLK When SER/PAR is HIGH, this pin, part of the Serial Port, is used as a serial data clock input or

output, dependent upon the logic state of the EXT/INT pin. The active edge where the data SDOUT
is updated depends upon the logic state of the INVSCLK pin.

23 D[10] DO When SER/PAR is LOW, this output is used as Bit 10 of the Parallel Port Data Output Bus.

or SYNC When SER/PAR is HIGH, this output, part of the Serial Port, is used as a digital output frame

synchronization for use with the internal data clock (EXT/INT = Logic LOW). When a read sequence
is initiated and INVSYNC is LOW, SYNC is driven HIGH and remains HIGH while SDOUT
output is valid. When a read sequence is initiated and INVSYNC is HIGH, SYNC is driven LOW
and remains LOW while SDOUT output is valid.

24 D[11] DO When SER/PAR is LOW, this output is used as Bit 11 of the Parallel Port Data Output Bus.

or RDERROR When SER/PAR is HIGH and EXT/INT is HIGH, this output, part of the Serial Port, is used as an

incomplete read error flag. In Slave Mode, when a data read is started and not complete when the
following conversion is complete, the current data is lost and RDERROR is pulsed HIGH.

25–28 D[12:15] DO Bit 12 to Bit 15 of the Parallel Port Data Output Bus. When SER/PAR is HIGH, these outputs are in

high impedance.

29 BUSY DO Busy Output. Transitions HIGH when a conversion is started and remains HIGH until the conversion

is complete and the data is latched into the on-chip shift register. The falling edge of BUSY could
be used as a data-ready clock signal.

30 DGND P Must Be Tied to Digital Ground.
31 RD DI Read Data. When CS and RD are both LOW, the Interface Parallel or Serial Output Bus is enabled.
32 CS DI Chip Select. When CS and RD are both LOW, the Interface Parallel or Serial Output Bus is enabled.

CS is also used to gate the external serial clock.

33 RESET DI Reset Input. When set to a logic HIGH, reset the AD7671. Current conversion, if any, is aborted.

If not used, this pin could be tied to DGND.

34 PD DI Power-Down Input. When set to a logic HIGH, power consumption is reduced and conversions are

inhibited after the current one is completed.

35 CNVST DI Start Conversion. A falling edge on CNVST puts the internal sample-and-hold into the hold state

and initiates a conversion. In Impulse Mode (IMPULSE HIGH and WARP LOW), if CNVST is
held LOW when the acquisition phase (t
hold state and a conversion is immediately started.

36 AGND P Must Be Tied to Analog Ground.

37 REF AI Reference Input Voltage.

38 REFGND AI Reference Input Analog Ground.

39 INGND P Analog Input Ground.

40, 41, INA, INB, AI Analog Inputs. Refer to Table I for input range configuration.
42, 43 INC, IND

NOTES
AI = Analog Input
DI = Digital Input
DI/O = Bidirectional Digital
DO = Digital Output
P = Power

) is complete, the internal sample-and-hold is put into the

8

REV. B

–7–

AD7671

DEFINITION OF SPECIFICATIONS
Integral Nonlinearity Error (INL)

Linearity error refers to the deviation of each individual code
from a line drawn from “negative full scale” through “positive
full scale.” The point used as negative full scale occurs 1/2 LSB
before the first code transition. Positive full scale is defined as a
level 1 1/2 LSB beyond the last code transition. The deviation is
measured from the middle of each code to the true straight line.

Differential Nonlinearity Error (DNL)

In an ideal ADC, code transitions are 1 LSB apart. Differential
nonlinearity is the maximum deviation from this ideal value. It is
often specified in terms of resolution for which no missing codes
are guaranteed.

Full-Scale Error

The last transition (from 011 ...10 to 011 . . . 11 in twos
complement coding) should occur for an analog voltage 1 1/2 LSB
below the nominal full scale (2.499886 V for the ± 2.5 V range).
The full-scale error is the deviation of the actual level of the last
transition from the ideal level.

Bipolar Zero Error

The difference between the ideal midscale input voltage (0 V) and
the actual voltage producing the midscale output code.

Unipolar Zero Error

In Unipolar Mode, the first transition should occur at a level
1/2 LSB above analog ground. The unipolar zero error is the
deviation of the actual transition from that point.

Spurious-Free Dynamic Range (SFDR)

The difference, in decibels (dB), between the rms amplitude of
the input signal and the peak spurious signal.

Effective Number of Bits (ENOB)

A measurement of the resolution with a sine wave input. It is
related to S/(N+D) by the following formula:

ENOB = (S/[N + D]

– 1.76)/6.02)

dB

and is expressed in bits.

Total Harmonic Distortion (THD)

The rms sum of the first five harmonic components to the rms
value of a full-scale input signal, expressed in decibels.

Signal-to-Noise Ratio (SNR)

The ratio of the rms value of the actual input signal to the rms
sum of all other spectral components below the Nyquist fre­quency, excluding harmonics and dc. The value for SNR is
expressed in decibels.

Signal-to-(Noise + Distortion) Ratio (S/[N+D])

The ratio of the rms value of the actual input signal to the rms
sum of all other spectral components below the Nyquist fre­quency, including harmonics but excluding dc. The value for
S/(N+D) is expressed in decibels.

Aperture Delay

A measure of the acquisition performance measured from the
falling edge of the CNVST input to when the input signal is
held for a conversion.

Transient Response

The time required for the AD7671 to achieve its rated accuracy
after a full-scale step function is applied to its input.

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REV. B