AD7856KRZ Datasheet AD7856ARSZ, AD7856KRZ, AD7856ARSZ-REEL7 | P31-P33

AD7856

–30–

REV. A

Avoid running digital lines under the device as these will couple

noise onto the die. The analog ground plane should be allowed

to run under the AD7856 to avoid noise coupling. The power

supply lines to the AD7856 should use as large a trace as pos-

sible to provide low impedance paths and reduce the effects of

glitches on the power supply line. Fast switching signals like

clocks should be shielded with digital ground to avoid radiating

noise to other sections of the board, and clock signals should

never be run near the analog inputs. Avoid crossover of digital

and analog signals. Traces on opposite sides of the board should

run at right angles to each other. This will reduce the effects of

feedthrough through the board. A microstrip technique is by far

the best, but is not always possible with a double-sided board.

In this technique, the component side of the board is dedicated

to ground planes while signals are placed on the solder side.

Good decoupling is also important. All analog supplies should

be decoupled with 10␣ µF tantalum in parallel with 0.1␣ µF ca-

pacitors to AGND. All digital supplies should have a 0.1␣ µF

disc ceramic capacitor to AGND. To achieve the best from

these decoupling components, they must be placed as close as

possible to the device, ideally right up against the device. In

systems where a common supply voltage is used to drive both

the AV

and DV

of the AD7856, it is recommended that

the system’s AV

supply be used. In this case there should be a

10 Ω resistor between the AV

pin and DV

pin. This supply

should have the recommended analog supply decoupling capaci-

tors between the AV

pin of the AD7856 and AGND and the

recommended digital supply decoupling capacitor between the

pin of the AD7856 and DGND.

Evaluating the AD7856 Performance

The recommended layout for the AD7856 is outlined in the

evaluation board for the AD7856. The evaluation board pack-

age includes a fully assembled and tested evaluation board,

documentation and software for controlling the board from the

PC via the EVAL-CONTROL BOARD. The EVAL-CON-

TROL BOARD can be used in conjunction with the AD7856

Evaluation board, as well as many other Analog Devices evalua-

tion boards ending in the CB designator, to demonstrate/evalu-

ate the ac and dc performance of the AD7856.

The software allows the user to perform ac (fast Fourier trans-

form) and dc (histogram of codes) tests on the AD7856. It also

gives full access to all the AD7856 on-chip registers allowing for

various calibration and power-down options to be programmed.

AD785x Family

12 bits, 200␣ kSPS, 3.0␣ V to 5.5␣ V:

AD7853 – Single-Channel Serial

AD7854 – Single-Channel Parallel

AD7858 – 8-Channel Serial

AD7859 – 8-Channel Parallel

14 bits, 333 kSPS, 4.75 V to 5.25 V:

AD7851 – Single-Channel Serial

AD7856

–31–REV. A

PAGE INDEX

Topic Page No.

FEATURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

GENERAL DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . 1

PRODUCT HIGHLIGHTS . . . . . . . . . . . . . . . . . . . . . . . . . 1

SPECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

TIMING SPECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . 4

TYPICAL TIMING DIAGRAMS . . . . . . . . . . . . . . . . . . . . 5

ABSOLUTE MAXIMUM RATINGS . . . . . . . . . . . . . . . . . 6

ORDERING GUIDE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

PIN CONFIGURATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . 6

PIN FUNCTION DESCRIPTIONS . . . . . . . . . . . . . . . . . . 7

TERMINOLOGY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

ON-CHIP REGISTERS

Addressing the On-Chip Registers . . . . . . . . . . . . . . . . . . . 9

CONTROL REGISTER . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

CONTROL REGISTER BIT FUNCTION

DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

STATUS REGISTER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

STATUS REGISTER BIT FUNCTION

DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

CALIBRATION REGISTERS . . . . . . . . . . . . . . . . . . . . . . 13

Addressing the Calibration Registers . . . . . . . . . . . . . . . . 13

Writing to/Reading from the Calibration Registers . . . . . . 13

Adjusting the Offset Calibration Register . . . . . . . . . . . . . 14

Adjusting the Gain Calibration Register . . . . . . . . . . . . . . 14

CIRCUIT INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . 15

CONVERTER DETAILS . . . . . . . . . . . . . . . . . . . . . . . . . . 15

TYPICAL CONNECTION DIAGRAM . . . . . . . . . . . . . . 15

ANALOG INPUT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Acquisition Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

DC/AC Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Input Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Transfer Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

REFERENCE SECTION . . . . . . . . . . . . . . . . . . . . . . . . . . 17

PERFORMANCE CURVES . . . . . . . . . . . . . . . . . . . . . . . . 18

POWER-DOWN OPTIONS . . . . . . . . . . . . . . . . . . . . . . . . 18

POWER-UP TIMES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Using an External Reference . . . . . . . . . . . . . . . . . . . . . . 19

Using the Internal (On-Chip) Reference . . . . . . . . . . . . . . 20

POWER VS. THROUGHPUT RATE . . . . . . . . . . . . . . . . 20

CALIBRATION SECTION

Calibration Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Automatic Calibration on Power-On . . . . . . . . . . . . . . . . . 21

Self-Calibration Description . . . . . . . . . . . . . . . . . . . . . . . 21

Self-Calibration Timing . . . . . . . . . . . . . . . . . . . . . . . . . . 21

System Calibration Description . . . . . . . . . . . . . . . . . . . . 22

System Gain and Offset Interaction . . . . . . . . . . . . . . . . . 22

System Calibration Timing . . . . . . . . . . . . . . . . . . . . . . . . 23

SERIAL INTERFACE SUMMARY . . . . . . . . . . . . . . . . . . 23

Resetting the Serial Interface . . . . . . . . . . . . . . . . . . . . . . 23

DETAILED TIMING SECTION

Mode 1 (2-Wire 8051 Interface) . . . . . . . . . . . . . . . . . . . . 24

Mode 2 (3-Wire SPI/QSPI Interface Mode) . . . . . . . . . . . 25

CONFIGURING THE AD7856 . . . . . . . . . . . . . . . . . . . . . 26

Writing to the AD7856 . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Interface Mode 1 Configuration . . . . . . . . . . . . . . . . . . . . 26

Interface Mode 2 Configuration . . . . . . . . . . . . . . . . . . . . 27

MICROPROCESSOR INTERFACING . . . . . . . . . . . . . . . 28

AD7856–8XC51 Interface . . . . . . . . . . . . . . . . . . . . . . . . 28

AD7856–68HC11/16/L11/PIC16C42 Interface . . . . . . . . 28

AD7856–ADSP-21xx Interface . . . . . . . . . . . . . . . . . . . . . 29

AD7856–DSP56000/1/2/L002 Interface . . . . . . . . . . . . . . 29

APPLICATION HINTS

Grounding and Layout . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Evaluating the AD7856 Performance . . . . . . . . . . . . . . . . 30

OUTLINE DIMENSIONS . . . . . . . . . . . . . . . . . . . . . . . . . 32

TABLE INDEX

Table Page No.

Table I. Write Register Addressing . . . . . . . . . . . . . . . . . . . . 9

Table II. Read Register Addressing . . . . . . . . . . . . . . . . . . . . 9

Table III. Channel Selection . . . . . . . . . . . . . . . . . . . . . . . . 11

Table IV. Calibration Selection . . . . . . . . . . . . . . . . . . . . . . 11

Table V. Calibration Register Addressing . . . . . . . . . . . . . . 13

Table VI. Power Management Options . . . . . . . . . . . . . . . . 19

Table VII. Power Consumption vs. Throughput . . . . . . . . . 20

Table VIII. Calibration Times (AD7856 with 6 MHz

CLKIN)␣ ␣ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Table IX. SCLK Active Edges . . . . . . . . . . . . . . . . . . . . . . . 23

Table X. Interface Mode Description . . . . . . . . . . . . . . . . . 24

AD7856

–32–

REV. A

OUTLINE DIMENSIONS

Dimensions shown in inches and (mm).

C3256a–0–7/98

PRINTED IN U.S.A.

24-Lead Plastic DIP

(N-24)

112

0.280 (7.11)

0.240 (6.10)

PIN 1

1.275 (32.30)

1.125 (28.60)

0.150

(3.81)

MIN

0.200 (5.05)

0.125 (3.18)

SEATING

PLANE

0.022 (0.558)

0.014 (0.356)

0.060 (1.52)

0.015 (0.38)

0.210

(5.33)

MAX

0.070 (1.77)

0.045 (1.15)

0.100 (2.54)

BSC

0.325 (8.25)

0.300 (7.62)

0.015 (0.381)

0.008 (0.204)

0.195 (4.95)

0.115 (2.93)

24-Lead Small Outline Package

(R-24)

0.6141 (15.60)

0.5985 (15.20)

0.4193 (10.65)

0.3937 (10.00)

0.2992 (7.60)

0.2914 (7.40)

PIN 1

SEATING

PLANE

0.0118 (0.30)

0.0040 (0.10)

0.0192 (0.49)

0.0138 (0.35)

0.1043 (2.65)

0.0926 (2.35)

0.0500

(1.27)

BSC

0.0125 (0.32)

0.0091 (0.23)

0.0500 (1.27)

0.0157 (0.40)

8°

0°

0.0291 (0.74)

0.0098 (0.25)

x 45°

24-Lead Shrink Small Outline Package

(RS-24)

0.328 (8.33)

0.318 (8.08)

0.311 (7.9)

0.301 (7.64)

0.212 (5.38)

0.205 (5.207)

PIN 1

SEATING

PLANE

0.008 (0.203)

0.002 (0.050)

0.07 (1.78)

0.066 (1.67)

0.0256

(0.65)

BSC

0.078 (1.98)

0.068 (1.73)

0.015 (0.38)

0.010 (0.25)

0.009 (0.229)

0.005 (0.127)

0.037 (0.94)

0.022 (0.559)

8°

0°

P1-P3 P4-P6 P7-P9 P10-P12 P13-P15 P16-P18 P19-P21 P22-P24 P25-P27 P28-P30 P31-P33

AD7856KRZ

Mfr. #:

Buy AD7856KRZ

Manufacturer:

Analog Devices Inc.

Description:

Analog to Digital Converters - ADC 5V SGL-Supply 8-Ch 14B 285kSPS

Lifecycle:

New from this manufacturer.

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AD7856KRZ

AD7856KRZ

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