Analog Devices AD7484 a Datasheet

3 MSPS, 14-Bit SAR ADC

FEATURES

Fast throughput rate: 3 MSPS
Wide input bandwidth: 40 MHz
No pipeline delays with SAR ADC
Excellent DC accuracy performance
Two parallel interface modes
Low power: 90 mW (full power) and 2.5 mW (NAP mode)
Standby mode: 2 µA max
Single 5 V supply operation
Internal 2.5 V reference
Full-scale overrange mode (using 15th bit)
System offset removal via user access offset register
Nominal 0 V to 2.5 V input with shifted range capability
Pin compatible upgrade of 12-Bit AD7482

GENERAL DESCRIPTION

The AD7484 is a 14-bit, high speed, low power, successive
approximation ADC. The part features a parallel interface
with throughput rates up to 3 MSPS. The part contains a low
noise, wide bandwidth track-and-hold that can handle input
frequencies in excess of 40 MHz.

The conversion process is a proprietary algorithmic successive
approximation technique that results in no pipeline delays.
The input signal is sampled and a conversion is initiated on
the falling edge of the

CONVST

is controlled via an internally trimmed oscillator. Interfacing
is via standard parallel signal lines, making the part directly
compatible with microcontrollers and DSPs.

The AD7484 provides excellent ac and dc performance
specifications. Factory trimming ensures high dc accuracy
resulting in very low INL, offset, and gain errors.

The part uses advanced design techniques to achieve very low
power dissipation at high throughput rates. Power consumption
in the normal mode of operation is 90 mW. There are two

Rev. A

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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
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registered trademarks are the property of their respective owners.

signal. The conversion process

AD7484

FUNCTIONAL BLOCK DIAGRAM

AV

AGND C

REFSEL

VIN

DD

REFERENCE

T/H

2.5V

BIASDVDD

14-BIT

ALGORITHMIC

BU

SAR

AD7484

MODE1

MODE2

CLIP

NAP

STBY

RESET

CONVST

CONTROL

LOGIC AND I/O

REGISTERS

CS

RD

BUSY

WRITE

D0

D1

D2

D3

Figure 1.

power saving modes: NAP mode, which keeps the reference
circuitry alive for a quick power-up while consuming 2.5 mW,
and standby mode, which reduces power consumption to a
mere 10 µW.

The AD7484 features an on-board 2.5 V reference but can also
accommodate an externally provided 2.5 V reference source.
The nominal analog input range is 0 V to 2.5 V, but an offset shift
capability allows this nominal range to be offset by ±200 mV. This
allows the user considerable flexibility in setting the bottom end
reference point of the signal range, a useful feature when using
single-supply op amps.

The AD7484 also provides the user with an 8% overrange
capability via a 15th bit. Therefore, if the analog input range
strays outside the nominal range by up to 8%, the user can still
accurately resolve the signal by using the 15th bit.

The AD7484 is powered by a 4.75 V to 5.25 V supply. The part
also provides a V

pin that allows the user to set the voltage

DRIVE

levels for the digital interface lines. The range for this V
is from 2.7 V to 5.25 V. The part is housed in a 48-lead LQFP
package and is specified over a −40°C to +85°C temperature
range.

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: [phone] www.analog.com
Fax: [phone] © 2004 Analog Devices, Inc. All rights reserved.

F

V

D4

DRIVE

D5

DGND

D6

REFOUT

REFIN

D14
D13
D12

D11
D10

D9
D8

D7

02642-0-001

DRIVE

pin

AD7484

TABLE OF CONTENTS

Specifications..................................................................................... 3

Circuit Description .................................................................... 12

Timing Characteristics..................................................................... 5

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

ESD Caution.................................................................................. 6

Pin Configuration and Function Descriptions............................. 7

Terminology ...................................................................................... 9

Typical Performance Characteristics ........................................... 10

REVISION HISTORY

2/04—Data Sheet changed from REV. 0 to REV. A

Updated Format......................................................... UNIVERSAL

Changes to Timing Characteristics............................................... 5

Changes to Pin Function Descriptions......................................... 8

Changes to Figure 9....................................................................... 11

Changes to the Converter Operation section ............................ 13

Changes to the Offset/Overrange section ..................................15

ADC Transfer Function............................................................. 13

Power Saving............................................................................... 13

Offset/Overrange........................................................................ 14

Parallel Interface ......................................................................... 15

Outline Dimensions....................................................................... 20

Ordering Guide .......................................................................... 20

8/02–Revision 0: Initial Version

Rev. A | Page 2 of 20

AD7484

SPECIFICATIONS

VDD = 5 V ± 5%, AGND = DGND = 0 V, V

5.25 V, unless otherwise noted. Table 1 temperature range is: −40°C to +85°C.

Table 1.

Parameter Specification Unit Test Conditions/Comments

DYNAMIC PERFORMANCE

1, 2

Signal-to-Noise + Distortion (SINAD)3 76.5 dB min FIN = 1 MHz
78 dB typ FIN = 1 MHz
79 dB typ FIN = 1 MHz, Extended Input
77 dB typ FIN = 1 MHz, Internal Reference
Total Harmonic Distortion (THD)3 −90 dB max

−95 dB typ

−92 dB typ Internal Reference
Peak Harmonic or Spurious Noise (SFDR)3 −90 dB max
Intermodulation Distortion (IMD)3

Second-Order Terms −96 dB typ F

Third-Order Terms −94 dB typ
Aperture Delay 10 ns typ
Full-Power Bandwidth 40 MHz typ @ 3 dB

3.5 MHz typ @ 0.1 dB
DC ACCURACY

Resolution 14 Bits
Integral Nonlinearity3 ±1 LSB max
±0.5 LSB typ
Differential Nonlinearity3 ±0.75 LSB max Guaranteed No Missed Codes to 14 Bits
±0.3 LSB typ
Offset Error3 ±6 LSB max

0.036 %FSR max
Gain Error3 ±6 LSB max

0.036 %FSR max
ANALOG INPUT

Input Voltage −200 mV min
+2.7 V max
DC Leakage Current ±1 µA max VIN from 0 V to 2.7 V
±2 µA typ VIN =−200 mV
Input Capacitance4 35 pF typ

REFERENCE INPUT/OUTPUT

V

Input Voltage +2.5 V ± 1% for Specified Performance

REFIN

V

Input DC Leakage Current ±1 µA max

REFIN

V

Input Capacitance4 25 pF typ

REFIN

V

Input Current 220 µA typ External Reference

REFIN

V

Output Voltage +2.5 V typ

REFOUT

V

Error @ 25°C ±50 mV typ

REFOUT

V

Error T

REFOUT

V

Output Impedance 1 Ω typ

REFOUT

MIN

to T

±100 mV max

MAX

LOGIC INPUTS

Input High Voltage, V
Input Low Voltage, V

V

INH

0.4 V max

INL

Input Current, IIN ±1 µA max
Input Capacitance, C

4

10 pF max

IN

= External, f

REF

= 3 MSPS; all specifications T

SAMPLE

−1 V min

DRIVE

to T

MIN

MAX

= 95.053 kHz, F

IN1

and valid for V

DRIVE

= 105.329 kHz

IN2

= 2.7 V to

Rev. A | Page 3 of 20

AD7484

Parameter Specification Unit Test Conditions/Comments

LOGIC OUTPUTS

Output High Voltage, VOH 0.7 × V
Output Low Voltage, VOL 0.3 × V
Floating-State Leakage Current ±10 µA max
Floating-State Output Capacitance4 10 pF max
Output Coding Straight (Natural) Binary

CONVERSION RATE

Conversion Time 300 ns max
Track-and-Hold Acquisition Time (t

) 70 ns max Sine Wave Input

ACQ

70 ns max Full-Scale Step Input

Throughput Rate 2.5 MSPS max Parallel Mode 1
3 MSPS max Parallel Mode 2
POWER REQUIREMENTS

VDD 5 V ± 5%

V

2.7 V min

DRIVE

5.25 V max

IDD

Normal Mode (Static) 12 mA max
Normal Mode (Operational) 18 mA max

NAP Mode 0.5 mA max
Standby Mode 2 µA max

0.5 µA typ

Power Dissipation

Normal Mode (Operational) 90 mW max
NAP Mode 2.5 mW max
Standby Mode5 10 µW max

1

SNR and SINAD figures quoted include external analog input circuit noise contribution of approximately 1 dB.

2

See Typical Performance Characteristics section for analog input circuits used.

3

See Terminology section.

4

Sample tested @ 25°C to ensure compliance.

5

Digital input levels at GND or V

DRIVE

.

V min

DRIVE

V max

DRIVE

CS

and RD = Logic 1

Rev. A | Page 4 of 20

AD7484

TIMING CHARACTERISTICS

VDD = 5 V ± 5%, AGND = DGND = 0 V, V
otherwise noted.

All timing specifications given in Table 2 are with a 25 pF load capacitance. With a load capacitance greater than this value, a digital buffer
or latch must be used.

Table 2.

Parameter Symbol Min Typ Max Unit

DATA READ

Conversion Time t
Quiet Time before Conversion Start t
CONVST

CONVST
CS

Pulse Width
Falling Edge to

BUSY

Falling Edge

Falling Edge to RD Falling Edge
Data Access Time t4 25 ns
CONVST

BUSY

Falling Edge to New Data Valid

Rising Edge to New Data Valid
Bus Relinquish Time t7 10 ns
RD

Rising Edge to CS Rising Edge

CS

Pulse Width

RD

Pulse Width

DATA WRITE

WRITE Pulse Width t9 5 ns
Data Setup Time t10 2 ns
Data Hold Time t11 6 ns
CS

Falling Edge to WRITE Falling Edge

WRITE Falling Edge to CS Rising Edge

= External; all specifications T

REF

to T

MIN

CONV

QUIET

t

5 100 ns

1

20 ns

t

2

0 ns

t

3

30 ns

t

5

5 ns

t

6

t

0 ns

8

t

14

t

15

t

12

t

13

and valid for V

MAX

= 2.7 V to 5.25 V, unless

DRIVE

300 ns
100 ns

30 ns
30 ns

5 ns
0 ns

Rev. A | Page 5 of 20

AD7484

ABSOLUTE MAXIMUM RATINGS

TA = 25°C, unless otherwise noted.

Table 3.

Parameter Rating

VDD to GND −0.3 V to +7 V
V

to GND −0.3 V to +7 V

DRIVE

Analog Input Voltage to GND −0.3 V to AVDD + 0.3 V
Digital Input Voltage to GND

REFIN to GND −0.3 V to AVDD + 0.3 V
Input Current to Any Pin except

Supplies
Operating Temperature Range

Commercial −40°C to +85°C
Storage Temperature Range −65°C to +150°C
Junction Temperature 150°C
θJA Thermal Impedance 50°C/W
θJC Thermal Impedance 10°C/W

Lead Temperature, Soldering

Vapor Phase (60 sec) 215°C

Infrared (15 sec) 220°C
ESD 1 kV

−0.3 V to V
V

±10 mA

DRIVE

+ 0.3

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.

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. A | Page 6 of 20