AD7854ARZ Datasheet AD7854ARZ, AD7854ARSZ, AD7854LARSZ | P25-P27

AD7854/AD7854L

REV. B

–25–

AD7854/AD7854L to DSP5600x

Figure 41 shows a parallel interface between the AD7854/

AD7854L and the DSP5600x series of DSPs. The AD7854/

AD7854L should be mapped into the top 64 locations of Y data

memory. If extra wait states are needed in this interface, they

can be programmed using the Port A bus control register (please

see DSP5600x User’s Manual for details). Data can be read

from the DSP5600x using the following instruction:

MOVE Y:ADCaddr, X0

Data can be written to the AD7854/AD7854L using the follow-

ing two instructions:

MOVE X0, Y:ADCaddr

MOVE X1, Y:ADCaddr+1

Where ADCaddr is the address in the DSP5600x address space

to which the AD7854/AD7854L has been mapped.

DSP56000/

DSP56002*

A15–A1

X/Y

IRQ

D23–D0

HBEN

BUSY

DB11–DB0

AD7854/

AD7854L*

ADDR

DECODE

ADDRESS BUS

DATA BUS

*ADDITIONAL PINS OMITTED FOR CLARITY

Figure 41. AD7854/AD7854L to DSP5600x Parallel Interface

AD7854/AD7854L to TMS320C30

Figure 40 shows a parallel interface between the AD7854/

AD7854L and the TMS320C3x family of DSPs. The

AD7854/AD7854L is interfaced to the Expansion Bus of the

TMS320C3x. Two wait states are required in this interface.

These can be programmed using the WTCNT bits of the

Expansion Bus Control register (see TMS320C3x Users Guide

for details). Data from the AD7854/AD7854L can be read

using the following instruction:

LDI *ARn,Rx

Data can be loaded into the AD7854/AD7854L using the

instructions:

STI Ry,*ARn++

STI Rz,*ARn--

where ARn is an auxiliary register containing the lower 16 bits

of the address of the AD7854/AD7854L in the TMS320C3x

memory space, Rx is the register into which the ADC data is

loaded during a load operation, Ry contains the 8 LSBs of

data and Rz contains the 8 MSBs of data to be written to the

AD7854/AD7854L.

TMS320C30*

XA12–XA1

XA0

IOSTRB

XR/W

INTx

XD23–XD0

HBEN

BUSY

DB11–DB0

AD7854/

AD7854L*

ADDR

DECODE

EXPANSION ADDRESS BUS

EXPANSION DATA BUS

*ADDITIONAL PINS OMITTED FOR CLARITY

Figure 40. AD7854/AD7854L to TMS320C30 Parallel

Interface

AD7854/AD7854L

–26–

REV. B

APPLICATION HINTS

Grounding and Layout

The analog and digital supplies of the AD7854/AD7854L are

independent and separately pinned out to minimize coupling

between the analog and digital sections of the device. The part

has very good immunity to noise on the power supplies as can

be seen by the PSRR versus frequency graph. However, care

should still be taken with regard to grounding and layout.

The printed circuit board on which the AD7854/AD7854L is

mounted should be designed such that the analog and digital

sections are separated and confined to certain areas of the

board. This facilitates the use of ground planes that can be

easily separated. A minimum etch technique is generally best

for ground planes as it gives the best shielding. Digital and

analog ground planes should only be joined in one place. If

the AD7854/AD7854L is the only device requiring an AGND

to DGND connection, then the ground planes should be

connected at the AGND and DGND pins of the AD7854/

AD7854L. If the AD7854/AD7854L is in a system where

multiple devices require AGND to DGND connections, the

connection should still be made at one point only, a star ground

point which should be established as close as possible to the

AD7854/AD7854L.

Avoid running digital lines under the device as these couple

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

to run under the AD7854/AD7854L to avoid noise coupling.

The power supply lines to the AD7854/AD7854L should use as

large a trace as possible to provide low impedance paths and

reduce the effects of glitches on the power supply line. Fast

switching signals like clocks and the data inputs 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 reduces 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 a 10 µF tantalum capacitor in parallel with

0.1 µF disc ceramic capacitor to AGND. All digital supplies

should have a 0.1 µF disc ceramic capacitor to DGND. To

achieve the best performance from these decoupling compo-

nents, 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

AD7854/AD7854L, it is recommended that the system’s AV

supply is used. In this case an optional 10 Ω resistor between

the AV

pin and DV

pin can help to filter noise from digital

circuitry. This supply should have the recommended analog

supply decoupling capacitors between the AV

pin of the

AD7854/AD7854L and AGND and the recommended digital

supply decoupling capacitor between the DV

pin of the

AD7854/AD7854L and DGND.

Evaluating the AD7854/AD7854L Performance

The recommended layout for the AD7854/AD7854L is outlined

in the evaluation board for the AD7854/AD7854L. The evalua-

tion board package 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-CONTROL BOARD can be used in conjunction

with the AD7854/AD7854L Evaluation board, as well as many

other Analog Devices evaluation boards ending in the CB desig-

nator, to demonstrate/evaluate the ac and dc performance of the

AD7854/AD7854L.

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

form) and dc (histogram of codes) tests on the AD7854/

AD7854L. It also gives full access to all the AD7854/AD7854L

on-chip registers allowing for various calibration and power-

down options to be programmed.

AD785x Family

All parts are 12 bits, 200 kSPS, 3.0 V to 5.5 V.

AD7853 – Single Channel Serial

AD7854 – Single Channel Parallel

AD7858 – Eight Channel Serial

AD7859 – Eight Channel Parallel

AD7854/AD7854L

REV. B

–27–

PAGE INDEX

Topic Page

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

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

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

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

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

ABSOLUTE MAXIMUM RATINGS . . . . . . . . . . . . . . . . . 5

ORDERING GUIDE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

PINOUTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

TERMINOLOGY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

PIN FUNCTION DESCRIPTION . . . . . . . . . . . . . . . . . . . 7

AD7854/AD7854L ON-CHIP REGISTERS . . . . . . . . . . . . 8

Addressing the On-Chip Registers . . . . . . . . . . . . . . . . . . . 8

Writing/Reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

CONTROL REGISTER . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

STATUS REGISTER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

CALIBRATION REGISTERS . . . . . . . . . . . . . . . . . . . . . . 11

Addressing the Calibration Registers . . . . . . . . . . . . . . . . 11

Writing to/Reading from the Calibration Registers . . . . . . 11

Adjusting the Offset Calibration Register . . . . . . . . . . . . . 12

Adjusting the Gain Calibration Register . . . . . . . . . . . . . . 12

CIRCUIT INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . 13

CONVERTER DETAILS . . . . . . . . . . . . . . . . . . . . . . . . . . 13

TYPICAL CONNECTION DIAGRAM . . . . . . . . . . . . . . 13

ANALOG INPUT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Acquisition Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

DC/AC Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Input Ranges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Transfer Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

REFERENCE SECTION . . . . . . . . . . . . . . . . . . . . . . . . . . 16

AD7854/AD7854L PERFORMANCE CURVES . . . . . . . . 16

POWER-DOWN OPTIONS . . . . . . . . . . . . . . . . . . . . . . . . 17

POWER-UP TIMES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Using an External Reference . . . . . . . . . . . . . . . . . . . . . . 17

Using the Internal (On-Chip) Reference . . . . . . . . . . . . . 18

POWER VS. THROUGHPUT RATE . . . . . . . . . . . . . . . . 18

Topic Page

CALIBRATION SECTION . . . . . . . . . . . . . . . . . . . . . . . . 20

Calibration Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Automatic Calibration on Power-On . . . . . . . . . . . . . . . . 20

Self-Calibration Description . . . . . . . . . . . . . . . . . . . . . . . 20

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

System Calibration Description . . . . . . . . . . . . . . . . . . . . 21

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

System Calibration Timing . . . . . . . . . . . . . . . . . . . . . . . 22

PARALLEL INTERFACE . . . . . . . . . . . . . . . . . . . . . . . . . 23

Reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Writing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Resetting the Parallel Interface . . . . . . . . . . . . . . . . . . . . . 23

MICROPROCESSOR INTERFACING . . . . . . . . . . . . . . . 24

AD7854/AD7854L to ADSP-21xx . . . . . . . . . . . . . . . . . . 24

AD7854/AD7854L to TMS32020, TMS320C25 and

TMS320C5x . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

AD7854/AD7854L to TMS320C30 . . . . . . . . . . . . . . . . 25

AD7854/AD7854L to DSP5600x . . . . . . . . . . . . . . . . . . 25

APPLICATIONS HINTS . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Grounding and Layout . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Evaluating the AD7854/AD7854L Performance . . . . . . . 26

INDEX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

OUTLINE DIMENSIONS . . . . . . . . . . . . . . . . . . . . . . . . . 28

TABLE INDEX

# Title Page

I Write Register Addressing . . . . . . . . . . . . . . . . . . . . . . . 8

II Read Register Addressing . . . . . . . . . . . . . . . . . . . . . . . 8

III Calibration Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

IV Calibrating Register Addressing . . . . . . . . . . . . . . . . . 11

V Analog Input Connections . . . . . . . . . . . . . . . . . . . . . 15

VI Power Management Options . . . . . . . . . . . . . . . . . . . . 17

VII Power Consumption vs. Throughput . . . . . . . . . . . . . 18

VIII Calibration Times (AD7854 with 4 MHz CLKIN) . . . 20

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

AD7854ARZ

Mfr. #:

Buy AD7854ARZ

Manufacturer:

Analog Devices Inc.

Description:

Analog to Digital Converters - ADC 3-5V SGL Supply 200kSPS 12B Parallel

Lifecycle:

New from this manufacturer.

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AD7854ARZ

AD7854ARZ

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