ANALOG DEVICES AD7824, AD7828 Service Manual

LC2MOS High Speed

www.BDTIC.com/ADI

a

FEATURES
4 or 8 Analog Input Channels
Built-In Track-and-Hold Function
10 kHz Signal Handling on Each Channel
Fast Microprocessor Interface
Single 5 V Supply
Low Power: 50 mW
Fast Conversion Rate: 2.5 ␮s/Channel
Tight Error Specification: 1/2 LSB

GENERAL DESCRIPTION

The AD7824 and AD7828 are high speed, multichannel, 8-bit
ADCs with a choice of four (AD7824) or eight (AD7828)
plexed analog inputs. A half-flash conversion technique gives a fast
conversion rate of 2.5 µs per channel, and the parts have a built-in
track-and-hold function capable of digitizing full-scale signals of
10 kHz (157 mV/µs slew rate) on all channels. The AD7824 and
AD7828 operate from a single 5 V supply and have an analog input
range of 0 V to 5 V, using an external 5 V reference.

Microprocessor interfacing of the parts is simple, using standard
Chip Select (CS) and Read (RD) signals to initiate the conversion
and read the data from the three-state data outputs. The half-flash
conversion technique means that there is no need to generate a
clock signal for the ADC. The AD7824 and AD7828 can be
interfaced easily to most popular microprocessors.

The AD7824 and AD7828 are fabricated in an advanced, all
ion-implanted, linear compatible CMOS process (LC2MOS) and
have low power dissipation of 40 mW (typ). The AD7824 is
available in a 0.3" wide, 24-lead “skinny” DIP, while the AD7828
is available in a 0.6" wide, 28-lead DIP and in 28-terminal
mount packages.

multi-

surface-

4- and 8-Channel 8-Bit ADCs

AD7824/AD7828

FUNCTIONAL BLOCK DIAGRAM

(+)

V

REF

(–)

V

REF

AIN1

AIN4

MUX*

AIN8

ADDRESS

LATCH

DECODE

A0 A1 A2**

*AD7824 – 4-CHANNEL MUX
**AD7828 – 8-CHANNEL MUX

A2 – AD7828 ONLY

V

REF

4-BIT

FLASH

ADC

(4MSB)

CS

THREE-

STATE

DRIVERS

4-BIT

DAC

(+)

4-BIT

16

FLASH

ADC

(4LSB)

TIMING AND CONTROL

CIRCUITRY

RDY

PRODUCT HIGHLIGHTS

1. 4- or 8-channel input multiplexer gives cost effective,
space-saving multichannel ADC system.

2. Fast conversion rate of 2.5 µs/channel features a per-channel
sampling frequency of 100 kHz for the AD7824 or 50 kHz
for the AD7828.

3.

Built-in track-and-hold function allows handling of four or
eight channels up to 10 kHz bandwidth (157 mV/µs slew rate).

4. Tight total unadjusted error spec and channel-to-channel
matching eliminate the need for user trims.

5. Single 5 V supply simplifies system power requirements.

6. Fast, easy-to-use digital interface allows connection to most
popular microprocessors with minimal external components.
No clock signal is required for the ADC.

RD

DB7
DB6
DB5
DB4

DB3
DB2
DB1
DB0

INT

REV. F

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.

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.

AD7824/AD7828–SPECIFICATIONS

www.BDTIC.com/ADI

noted. All specifications T

MIN

to T

, unless otherwise noted. Specifications apply to Mode 0.)

MAX

(VDD = 5 V, V

(+) = 5 V, V

REF

(–) = GND = O V, unless otherwise

REF

Parameter K Version1L Version B, T Versions C, U Versions Unit Conditions/Comments

ACCURACY

Resolution 8 8 8 8 Bits
Total Unadjusted Error

2

± 1 ± 1/2 ± 1 ± 1/2 LSB max

Minimum Resolution for which

No Missing Codes Are Guaranteed 8 8 8 8 Bits

Channel-to-Channel Mismatch ± 1/4 ± 1/4 ± 1/4 ± 1/4 LSB max

REFERENCE INPUT

Input Resistance 1.0/4.0 1.0/4.0 1.0/4.0 1.0/4.0 kΩ min/kΩ max

(+) Input Voltage Range V

V

REF

V

(–) Input Voltage Range GND/ GND/ GND/ GND/ V min/V max

REF

REF

V

DD

V

REF

(–)/ V

(+) V

REF

V

DD

REF

(–)/ V

(+) V

(–)/ V

REF

V

DD

(+) V

REF

(–)/ V min/V max

REF

V

DD

(+)

REF

ANALOG INPUT

Input Voltage Range V

Input Leakage Current ± 3 ± 3 ± 3 ± 3 µA max Analog Input Any Channel
Input Capacitance

3

REF

V

REF

(–)/ V
(+) V

REF

REF

(–)/ V
(+) V

(–)/ V

REF

(+) V

REF

(–)/ V min/V max

REF

(+)

REF

45 45 45 45 pF typ 0 V to 5 V

LOGIC INPUTS

RD, CS, A0, A1, and A2

V

INH

V

INL

I

INH

I

INL

Input Capacitance

3

2.4 2.4 2.4 2.4 V min

0.8 0.8 0.8 0.8 V max
111 1 µA max
–1 –1 –1 –1 µA max
8888pF max Typically 5 pF

LOGIC OUTPUTS

DB0–DB7 and INT

V

OH

V

OL

(DB0–DB7) ± 3 ± 3 ± 3 ± 3 µA max Floating State Leakage

I

OUT

Output Capacitance
RDY

4

V

OL

I

OUT

3

4.0 4.0 4.0 4.0 V min I

0.4 0.4 0.4 0.4 V max I

8888pF max Typically 5 pF

0.4 0.4 0.4 0.4 V max I
± 3 ± 3 ± 3 ± 3 µA max Floating State Leakage

SOURCE

= 1.6 mA

SINK

= 2.6 mA

SINK

= 360 µA

Output Capacitance 8 8 8 8 pF max Typically 5 pF

SLEW RATE, TRACKING

3

0.7 0.7 0.7 0.7 V/µs typ

0.157 0.157 0.157 0.157 V/µs max

POWER SUPPLY

V

DD

5

I

DD

555 5 V ± 5% for Specified

Performance

16 16 20 20 mA max CS = RD = 2.4 V

Power Dissipation 50 50 50 50 mW typ

80 80 100 100 mW max

Power Supply Sensitivity ± 1/4 ±1/4 ± 1/4 ±1/4 LSB max ± 1/16 LSB typ

VDD = 5 V ± 5%

NOTES

1

Temperature ranges are as follows: K, L Versions: 0°C to 70°C

2

Total Unadjusted Error includes offset, full-scale and linearity errors.

3

Sample tested at 25°C by Product Assurance to ensure compliance.

4

RDY is an open-drain output.

5

See Typical Performance Characteristics.

Specifications subject to change without notice.

B, C Versions: –40°C to +85°C
T, U Versions: –55°C to +125°C

–2–

REV. F

AD7824/AD7828

www.BDTIC.com/ADI

1

TIMING CHARACTERISTICS

Limit at 25ⴗC Limit at T

(VDD = 5 V; V

, T

MIN

Parameter (All Grades) (K, L, B, C Grades) (T, U Grades) Unit Conditions/Comments

t

CSS

t

CSH

t

AS

t

AH

t

RDY

t

CRD

t

ACC1

t

ACC2

t

lNTH

t

DH

t

P

t

RD

2

3

3

2

4

00 0 ns min CS to RD Setup Time
00 0 ns min CS to RD Hold Time
00 0 ns min Multiplexer Address Setup Time
30 35 40 ns min Multiplexer Address Hold Time
40 60 60 ns max CS to RDY Delay. Pull-Up

2.0 2.4 2.8 µs max Conversion Time, Mode 0
85 110 120 ns max Data Access Time after RD
50 60 70 ns max Data Access Time after INT, Mode 0
40 65 70 ns typ RD to INT Delay
75 100 100 ns max
60 70 70 ns max Data Hold Time
500 500 600 ns min Delay Time between Conversions
60 80 80 ns min Read Pulsewidth, Mode 1
600 500 400 ns max

NOTES

1

Sample tested at 25°C to ensure compliance. All input control signals are specified with t

2

CL = 50 pF.

3

Measured with load circuits of Figure 1 and defined as the time required for an output to cross 0.8 V or 2.4 V.

4

Defined as the time required for the data lines to change 0.5 V when loaded with the circuits of Figure 2.

Specifications subject to change without notice.

REF

MAX

(+) = 5 V; V

Limit at T

(–) = GND = 0 V, unless otherwise noted.)

REF

, T

MIN

MAX

Resistor 5 kΩ.

= t

RISE

= 20 ns (10% to 90% of 5 V) and timed from a voltage level of 1.6 V.

FALL

Test Circuits

DBN

3k⍀ 100pF

DGND

a. High-Z to V

DBN

b. High-Z to V

Figure 1. Load Circuits for Data Access Time Test

OH

5V

3k⍀

100pF

DGND

OL

DBN

3k⍀ 10pF

DGND

a. VOH to High-Z

5V

3k⍀

DBN

10pF

DGND

b. VOL to High-Z

Figure 2. Load Circuits for Data Hold Time Test

REV. F

–3–

AD7824/AD7828

www.BDTIC.com/ADI

ABSOLUTE MAXIMUM RATINGS*

(TA = 25°C, unless otherwise noted.)

VDD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 V, 7 V

Digital Input Voltage to GND

(RD, CS, A0, A1, and A2) . . . . . . . . . –0.3 V, V

+ 0.3 V

DD

Digital Output Voltage to GND

(DB0, DB7, RDY, and INT) . . . . . . . –0.3 V, V

V

(+) to GND . . . . . . . . . . . . . . . . . V

REF

(–) to GND . . . . . . . . . . . . . . . . . . . . . . . . 0 V, V

V

REF

(–), VDD + 0.3 V

REF

Analog Input (Any Channel) . . . . . . . . . . –0.3 V, V

+ 0.3 V

DD

REF

+ 0.3 V

DD

(+)

Operating Temperature Range

Commercial (K, L Versions) . . . . . . . . . . . . . . 0°C to 70°C

Industrial (B, C Versions) . . . . . . . . . . . . . –40°C to +85°C

Extended (T, U Versions) . . . . . . . . . . . . –55°C to +125°C

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

Lead Temperature (Soldering, 10 secs) . . . . . . . . . . . . 300°C

Power Dissipation (Any Package) to 75°C . . . . . . . . . 450 mW

Derates above 75°C by . . . . . . . . . . . . . . . . . . . . . . 6 mW/°C

*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 sections of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect device reliability.

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 AD7824/AD7828 feature 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.

PIN CONFIGURATIONS

ORDERING GUIDE

DIP/SOIC/SSOP

Temperature Unadjusted Package

1

AIN4 V

2

AIN3 NC

3

AIN2 A0

4

AIN1 A1

5

NC DB7

AD7824

6

DB0 DB6

TOP VIEW

(Not to Scale)

7

DB1 DB5

8

DB2 DB4

9

DB3

10

RD

11

INT

12

GND V

NC = NO CONNECT

24

23

22

21

20

19

18

17

16

CS

15

RDY

14

V

13

PLCC

DD

REF

REF

1

AIN6

2

AIN5

3

AIN4

4

AIN3

5

AIN2

6

AIN1

DB0

DB1

DB2

(+)

(–)

DB3

GND

AD7828

7

NC

TOP VIEW

(Not to Scale)

8

9

10

11

12

RD

13

INT

14

NC = NO CONNECT

28

AIN7

27

AIN8

26

V

DD

25

A0

24

A1

23

A2

22

DB7

21

DB6

20

DB5

19

DB4

18

CS

17

RDY

16

V

(+)

REF

15

V

(–)

REF

Model Range Error (LSBs) Option

AD7824KN 0°C to 70°C ± 1 N-24
AD7824LN 0°C to 70°C ± 1/2 N-24
AD7824KR 0°C to 70°C ± 1 R-24
AD7824BQ –40°C to +85°C ± 1 Q-24
AD7824CQ –40°C to +85°C ± 1/2 Q-24
AD7824TQ* –55°C to +125°C ± 1 Q-24
AD7824UQ* –55°C to +125°C ± 1/2 Q-24

AD7828KN 0°C to 70°C ± 1 N-28
AD7828LN 0°C to 70°C ± 1/2 N-28
AD7828KP 0°C to 70°C ± 1 P-28A
AD7828LP 0°C to 70°C ± 1/2 P-28A
AD7828BQ –40°C to +85°C ± 1 Q-28
AD7828CQ –40°C to +85°C ± 1/2 Q-28
AD7828BR –40°C to +85°C+1 R-28
AD7828LRS 0°C to 70°C ± 1/2 RS-28
AD7828TQ* –55°C to +125°C ± 1 Q-28
AD7828UQ* –55°C to +125°C ± 1/2 Q-28
AD7828TE* –55°C to +125°C ± 1 E-28A
AD7828UE* –55°C to +125°C ± 1/2 E-28A

*Available to /883B processing only. Contact our local sales office for military

data sheet. For U.S. Standard Military Drawing (SMD) see DESC Drawing
#5692-88764.

AIN2

AIN1

NC

DB0

DB1

DB2

DB3

AIN5

AIN4

AIN3

4 3 2 1 28 27 26

5

6

7

8

9

10

11

AD7828

TOP VIEW

(Not to Scale)

12 13 14 15 16 17 18

RD

INT

GND

NC = NO CONNECT

AIN7

AIN6

PIN 1
IDENTIFIER

(–)

(+)

REF

REF

V

V

AIN8

RDY

DD

V

25

A0

24

A1

23

A2

22

DB7

21

DB6

20

DB5

19

DB4

CS

5

AIN2

6

AIN1

7

NC A2

8

DB0 DB7

9

DB1

10

DB2

11

DB3 DB4

LCCC

AIN6

AIN5

AIN4

AIN3

2

28 271

3426

AD7828

TOP VIEW

(Not to Scale)

AIN7

AIN8

DD

V

25

A0

24

A1

23

22

21

DB6

20

DB5

19

WARNING!

ESD SENSITIVE DEVICE

Total

12

13 14 15 16 17 18

REF

(+)

V

REF

CS

RDY

RD

(–)

INT

GND

V

NC = NO CONNECT

–4–

REV. F

Typical Performance Characteristics–AD7824/AD7828

TA – AMBIENT TEMPERATURE – ⴗC

14

12

10

–100 150–50

I

DD

– SUPPLY CURRENT – mA

050100

13

11

9

8

VDD = 5.25V

VDD = 4.75V

VDD = 5V

t

P

– ns

2.0

1.0

0

300

LINEARITY ERROR – LSB

1.5

0.5

VDD = 5V
V

REF

= 5V

T

A

= 25ⴗC

400 500 600 700 800 900

www.BDTIC.com/ADI

3

2

– CONVERSION TIME – ␮s

CRD

t

1
–100 150–50

TA – AMBIENT TEMPERATURE – ⴗC

050100

= 5V

V

DD

TPC 1. Conversion Time vs. Temperature

2.0

1.5

1.0

0.5

LINEARITY ERROR – LSB*

0

051

V

REF

*1LSB =

256

TPC 2. Accuracy vs. V

234

V

– V

REF

[V

REF

= V

REF

REF

VDD = 5V

= 25ⴗC

T

A

(+) – V

REF

(–)]

TPC 4. Power Supply Current vs. Temperature
(Not Including Reference Ladder)

TPC 5. Accuracy vs. t

P

–36

ENCODE RATE = 400kHz
INPUT SIGNAL = 5V p-p

–38

MEASUREMENT BANDWIDTH = 80kHz

–40

–42

–44

SNR – dB

–46

REV. F

–48

–50

–52

TPC 3. Signal Noise Ratio vs. Input Frequency

234

51

INPUT FREQUENCY – kHz

20 30 40 50 70 100710

–5–

10

8

6

4

OUTPUT CURRENT – mA

2

0

–100 150–50

TA – AMBIENT TEMPERATURE – ⴗC

TPC 6. Output Current vs. Temperature

V

DD

I

, V

SOURCE

I

SINK

050100

= 2.4V

OUT

, V

= 0.4V

OUT

= 5V