AD7891BS-1 Analog Devices Inc, AD7891BS-1 Datasheet

AD7891BS-1

Manufacturer Part Number

AD7891BS-1

Description

IC DAS 12BIT 8CH 44-MQFP

Manufacturer

Analog Devices Inc

Type

Data Acquisition System (DAS)r

Datasheet

1.AD7891BSZ-2.pdf (20 pages)

Specifications of AD7891BS-1

Rohs Status

RoHS non-compliant

Resolution (bits)

12 b

Sampling Rate (per Second)

500k

Data Interface

Serial, Parallel

Voltage Supply Source

Single Supply

Voltage - Supply

Operating Temperature

-40°C ~ 85°C

Mounting Type

Surface Mount

Package / Case

44-MQFP, 44-PQFP

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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 owners.

GENERAL DESCRIPTION

The AD7891 is an 8-channel, 12-bit data acquisition system

with a choice of either parallel or serial interface structure. The

part contains an input multiplexer, an on-chip track/hold ampli-

fier, a high speed 12-bit ADC, a 2.5 V reference, and a high

speed interface. The part operates from a single 5 V supply and

accepts a variety of analog input ranges across two models, the

AD7891-1 (± 5 V and ± 10 V) and the AD7891-2 (0 V to +2.5 V,

0 V to +5 V, and ± 2.5 V).

The AD7891 provides the option of either a parallel or serial

interface structure determined by the MODE pin. The part

has standard control inputs and fast data access times for both

the serial and parallel interfaces, ensuring easy interfacing to

modern microprocessors, microcontrollers, and digital signal

processors.

In addition to the traditional dc accuracy specifications, such as

linearity, full-scale and offset errors, the part is also specified for

dynamic performance parameters, including harmonic distortion

and signal-to-noise ratio.

Power dissipation in normal mode is 82 mW typical; in

the standby mode, this is reduced to 75 mW typ. The part is

available in a 44-terminal MQFP and a 44-lead PLCC.

REV. D

FEATURES

Fast 12-Bit ADC with 1.6 s Conversion Time

8 Single-Ended Analog Input Channels

Overvoltage Protection on Each Channel

Selection of Input Ranges:

Parallel and Serial Interface

On-Chip Track/Hold Amplifier

On-Chip Reference

Single-Supply, Low Power Operation (100 mW Max)

Power-Down Mode (75 W Typ)

APPLICATIONS

Data Acquisition Systems

Motor Control

Mobile Communication Base Stations

Instrumentation

0 to +2.5 V, 0 to +5 V,

5 V,

10 V for AD7891-1

2.5 V for AD7891-2

High Speed Data Acquisition System

PRODUCT HIGHLIGHTS

1. The AD7891 is a complete monolithic 12-bit data acquisition

2. The AD7891-2 features a conversion time of 1.6 ms and an

3. Each channel on the AD7891 has overvoltage protection. This

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.

Tel: 781/329-4700

Fax: 781/326-8703

IN1A

IN1B

IN2A

IN2B

IN3A

IN3B

IN4A

IN4B

IN5A

IN5B

IN6A

IN6B

IN7A

IN7B

IN8A

IN8B

system that combines an 8-channel multiplexer, 12-bit ADC,

2.5 V reference, and track/hold amplifier on a single chip.

acquisition time of 0.4 ms. This allows a sample rate of

500 kSPS when sampling one channel and 62.5 kSPS when

channel hopping. These sample rates can be achieved using

either a software or hardware convert start. The AD7891-1

has an acquisition time of 0.6 ms when using a hardware

convert start and an acquisition time of 0.7 ms when using a

software convert start. These acquisition times allow sample

rates of 454.5 kSPS and 435 kSPS, respectively, for hardware

and software convert start.

means an overvoltage on an unselected channel does not affect

the conversion on a selected channel. The AD7891-1 can

withstand overvoltages of ± 17 V.

WR CS RD EOC CONVST MODE

FUNCTIONAL BLOCK DIAGRAM

CONTROL LOGIC

MOS 8-Channel, 12-Bit

AD7891

ADDRESS

DECODE

REF OUT/

TRACK/HOLD

REF IN

REFERENCE

REF GND

AGND AGND DGND

2.5V

CLOCK

12-BIT

ADC

AD7891

www.analog.com

STANDBY

DATA/

CONTROL

LINES

Related parts for AD7891BS-1

AD7891BS-1 Summary of contents

Page 1

FEATURES Fast 12-Bit ADC with 1.6 s Conversion Time 8 Single-Ended Analog Input Channels Overvoltage Protection on Each Channel Selection of Input Ranges for AD7891 +2 2.5 V ...

AD7891–SPECIFICATIONS Parameter 2 DYNAMIC PERFORMANCE 4 Signal-to-(Noise + Distortion) Ratio @ 25∞ MIN MAX 4 Total Harmonic Distortion 4 Peak Harmonic or Spurious Noise 4 Intermodulation Distortion Second-Order Terms Third-Order Terms 4 Channel-to-Channel Isolation DC ACCURACY Resolution ...

Page 3

Parameter A Version LOGIC OUTPUTS Output High Voltage, V 4.0 OH Output Low Voltage, V 0.4 OL DB11to DB0 ± 10 Floating-State Leakage Current 5 Floating-State Capacitance 15 Output Coding Straight (Natural) Binary CONVERSION RATE Conversion Time 1.6 Track/Hold Acquisition ...

Page 4

AD7891 TIMING CHARACTERISTICS Parameter Versions t 1.6 CONV Parallel Interface ...

Page 5

... Model Input Range AD7891ACHIPS-1 AD7891ACHIPS-2 ± ± AD7891AS-1 ± ± AD7891ASZ-1 ± ± AD7891AP-1 ± ± AD7891AP-1REEL ± ± AD7891BS-1 ± ± AD7891BP-1 ± ± AD7891BP-1REEL ± ± AD7891YS-1 ± ± AD7891YS-1REEL ± ± AD7891YP-1 ± ± AD7891YP-1REEL +2.5 V, ± 2.5 V AD7891AS +2.5 V, ± ...

Page 6

AD7891 PLCC MQFP Pin No. Pin No. Mnemonic 1–5 28– INXA INXB 34– AGND 20 14 DGND STANDBY REF OUT/REF ...

Page 7

PLCC Pin No. MQFP Pin No. Mnemonic Data I/O Lines There are 12 data input/output lines on the AD7891. When the part is configured for parallel ...

Page 8

AD7891 SERIAL INTERFACE MODE FUNCTIONS When the part is configured for serial mode (MODE = 0), five of the 12 data input/output lines provide serial interface functions. These functions are outlined below. PLCC Pin No. MQFP Pin No. Mnemonic 18 ...

Page 9

TERMINOLOGY Signal-to-(Noise + Distortion) Ratio This is the measured ratio of signal to (noise + distortion) at the output of the ADC. The signal is the rms amplitude of the fundamental. Noise is the rms sum of all nonfundamental signals ...

Page 10

AD7891 CONVERTER DETAILS The AD7891 is an 8-channel, high speed, 12-bit data acquisi- tion system. It provides the user with signal scaling, multiplexer, track/hold, reference, ADC, and high speed parallel and serial interface logic functions on a single chip. The ...

Page 11

Serial Interface Mode The serial interface mode is selected by tying the MODE input to a logic low. In this case, five of the data/control inputs of the parallel mode assume serial interface functions. The serial interface on the AD7891 ...

Page 12

AD7891 CIRCUIT DESCRIPTION Reference The AD7891 contains a single reference pin labeled REF OUT/ REF IN that either provides access to the part’s own 2.5 V internal reference or to which an external 2.5 V reference can be connected to ...

Page 13

Table I. Ideal Code Transition Table for the AD7891-1, Analog Input Input Voltage 2 3 +FSR /2 – 3/2 LSB (9.99268 V, 4.99634 V or 2.49817 V) +FSR/2 – 5/2 LSB (9.98779 V, 4.99390 V or 2.49695 V) +FSR/2 – ...

Page 14

AD7891 Track/Hold Amplifier The track/hold amplifier on the AD7891 allows the ADC to accurately convert an input sine wave of full-scale amplitude to 12-bit accuracy. The input bandwidth of the track/hold is greater than the Nyquist rate of the ADC ...

Page 15

As in the 8X51 circuit in Figure 7, the way the 68HC11 is informed that a conversion is completed is not shown in the diagram. The EOC line can be used to inform the 68HC11 that a conversion is complete ...

Page 16

AD7891 PARALLEL INTERFACING The parallel port on the AD7891 allows the device to be interfaced to microprocessors or DSP processors as a memory mapped or I/O mapped device. The CS and RD inputs are common to all memory peripheral interfacing. ...

Page 17

AD7891 to DSP5600x Figure 15 shows a parallel interface between the AD7891 and the DSP5600x series of DSPs. The AD7891 should be mapped into the top 64 locations of Y data memory. If extra wait states are needed in this ...

Page 18

AD7891 AD7891 PERFORMANCE Linearity The linearity of the AD7891 is primarily determined by the on-chip 12-bit DAC. This is a segmented DAC that is laser trimmed for 12-bit integral linearity and differential linearity. Typical INL for the AD7891 is ± ...

Page 19

Effective Number of Bits The formula for signal-to-(noise + distortion) ratio (see Terminology section) is related to the resolution or number of bits of the converter. Rewriting the formula gives a measure of performance expressed in effective number of bits ...

Page 20

AD7891 2.10 2.00 1.95 0.25 MIN VIEW A ROTATED 90 CCW Revision History Location 4/04—Data Sheet changed from REV REV. D. Changes to SPECIFICATIONS . . . . . . . . . . . . . . ...

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