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
LC MOS High Speed
4- and 8-Channel 8-Bit ADCs
AD7824/AD7828
FUNCTIONAL BLOCK DIAGRAM
V
REF
(+)
V
REF
(–)
AIN1
AIN4
4-BIT
FLASH
ADC
(4MSB)
4-BIT
DAC
V
REF
(+)
16
4-BIT
FLASH
ADC
(4LSB)
TIMING AND CONTROL
CIRCUITRY
RDY
CS
RD
THREE-
STATE
DRIVERS
DB3
DB2
DB1
DB0
INT
DB7
DB6
DB5
DB4
2
MUX*
AIN8
ADDRESS
LATCH
DECODE
A0 A1 A2**
*AD7824
– 4-CHANNEL MUX
**AD7828
– 8-CHANNEL MUX
A2 – AD7828 ONLY
GENERAL DESCRIPTION
PRODUCT HIGHLIGHTS
The AD7824 and AD7828 are high speed, multichannel, 8-bit
ADCs with a choice of four (AD7824) or eight (AD7828) multi-
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 (LC
2
MOS) 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 surface-
mount packages.
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.
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: 781/329-4700
www.analog.com
Fax: 781/326-8703
© 2003 Analog Devices, Inc. All rights reserved.
=
V
AD7824/AD7828–SPECIFICATIONS
(Vapply5toV,Mode(+) = 5 V, V
noted. All specifications T to T , unless otherwise noted. Specifications
0.)
DD
REF
MIN
MAX
REF
(–) = GND = O V, unless otherwise
Conditions/Comments
Parameter
ACCURACY
Resolution
Total Unadjusted Error
2
Minimum Resolution for which
No Missing Codes Are Guaranteed
Channel-to-Channel Mismatch
REFERENCE INPUT
Input Resistance
V
REF
(+) Input Voltage Range
V
REF
(–) Input Voltage Range
ANALOG INPUT
Input Voltage Range
Input Leakage Current
Input Capacitance
3
LOGIC INPUTS
RD, CS,
A0, A1, and A2
V
INH
V
INL
I
INH
I
INL
Input Capacitance
3
LOGIC OUTPUTS
DB0–DB7 and
INT
V
OH
V
OL
I
OUT
(DB0–DB7)
Output Capacitance
3
RDY
V
OL4
I
OUT
Output Capacitance
SLEW RATE, TRACKING
3
POWER SUPPLY
V
DD
I
DD5
Power Dissipation
Power Supply Sensitivity
NOTES
1
Temperature ranges are as follows:
K Version
1
L Version B, T Versions
8
±
1
8
±
1/4
1.0/4.0
V
REF
(–)/
V
DD
GND/
V
REF
(+)
V
REF
(–)/
V
REF
(+)
±
3
45
8
±
1/2
8
±
1/4
1.0/4.0
V
REF
(–)/
V
DD
GND/
V
REF
(+)
V
REF
(–)/
V
REF
(+)
±
3
45
8
±
1
8
±
1/4
1.0/4.0
V
REF
(–)/
V
DD
GND/
V
REF
(+)
V
REF
(–)/
V
REF
(+)
±
3
45
C, U Versions Unit
8
±
1/2
8
±
1/4
1.0/4.0
V
REF
(–)/
V
DD
GND/
V
REF
(+)
V
REF
(–)/
V
REF
(+)
±
3
45
Bits
LSB max
Bits
LSB max
kΩ min/kΩ max
V min/V max
V min/V max
V min/V max
µA
max
pF typ
Analog Input Any Channel
0 V to 5 V
2.4
0.8
1
–1
8
2.4
0.8
1
–1
8
2.4
0.8
1
–1
8
2.4
0.8
1
–1
8
V min
V max
µA
max
µA
max
pF max
Typically 5 pF
4.0
0.4
±
3
8
0.4
±
3
8
0.7
0.157
5
16
50
80
±
1/4
4.0
0.4
±
3
8
0.4
±
3
8
0.7
0.157
5
16
50
80
±
1/4
4.0
0.4
±
3
8
0.4
±
3
8
0.7
0.157
5
20
50
100
±
1/4
4.0
0.4
±
3
8
0.4
±
3
8
0.7
0.157
5
20
50
100
±
1/4
V min
V max
µA
max
pF max
V max
µA
max
pF max
V/µs typ
V/µs max
V
mA max
mW typ
mW max
LSB max
I
SOURCE
= 360
µA
I
SINK
= 1.6 mA
Floating State Leakage
Typically 5 pF
I
SINK
= 2.6 mA
Floating State Leakage
Typically 5 pF
±
5% for Specified
Performance
CS
=
RD
= 2.4 V
±
1/16 LSB typ
V
DD
= 5 V
±
5%
K, L Versions: 0°C to 70°C
B, C Versions: –40°C to +85°C
T, U Versions: –55°C to +125°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.
–2–
REV. F
AD7824/AD7828
TIMING CHARACTERISTICS
1
(V
Parameter
t
CSS
t
CSH
t
AS
t
AH
t
RDY2
t
CRD
t
ACC13
t
ACC23
t
lNTH2
t
DH4
t
P
t
RD
Limit at 25 C
(All Grades)
0
0
0
30
40
2.0
85
50
40
75
60
500
60
600
0
0
0
35
60
2.4
110
60
65
100
70
500
80
500
DD
= 5 V; V
REF
(+) = 5 V; V
REF
(–) = GND = 0 V, unless otherwise noted.)
Limit at T
MIN
, T
MAX
(T, U Grades)
0
0
0
40
60
2.8
120
70
70
100
70
600
80
400
Unit
ns min
ns min
ns min
ns min
ns max
µs
max
ns max
ns max
ns typ
ns max
ns max
ns min
ns min
ns max
Conditions/Comments
CS
to
RD
Setup Time
CS
to
RD
Hold Time
Multiplexer Address Setup Time
Multiplexer Address Hold Time
CS
to RDY Delay. Pull-Up
Resistor 5 kΩ.
Conversion Time, Mode 0
Data Access Time after
RD
Data Access Time after
INT,
Mode 0
RD
to
INT
Delay
Data Hold Time
Delay Time between Conversions
Read Pulsewidth, Mode 1
Limit at T
MIN
, T
MAX
(K, L, B, C Grades)
NOTES
1
Sample tested at 25°C to ensure compliance. All input control signals are specified with t
RISE
= t
FALL
= 20 ns (10% to 90% of 5 V) and timed from a voltage level of 1.6 V.
2
C
L
= 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.
Test Circuits
DBN
3k
DGND
100pF
DBN
3k
DGND
10pF
a. High-Z to V
OH
a. V
OH
to High-Z
5V
3k
DBN
100pF
DGND
DBN
5V
3k
10pF
DGND
b. High-Z to V
OL
Figure 1. Load Circuits for Data Access Time Test
b. V
OL
to High-Z
Figure 2. Load Circuits for Data Hold Time Test
REV. F
–3–
AD7824/AD7828
ABSOLUTE MAXIMUM RATINGS*
(T
A
= 25°C, unless otherwise noted.)
V
DD
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 V, 7 V
Digital Input Voltage to GND
(RD,
CS,
A0, A1, and A2) . . . . . . . . . –0.3 V, V
DD
+ 0.3 V
Digital Output Voltage to GND
(DB0, DB7, RDY, and
INT)
. . . . . . . –0.3 V, V
DD
+ 0.3 V
V
REF
(+) to GND . . . . . . . . . . . . . . . . . V
REF
(–), V
DD
+ 0.3 V
V
REF
(–) to GND . . . . . . . . . . . . . . . . . . . . . . . . 0 V, V
REF
(+)
Analog Input (Any Channel) . . . . . . . . . . –0.3 V, V
DD
+ 0.3 V
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.
WARNING!
ESD SENSITIVE DEVICE
PIN CONFIGURATIONS
DIP/SOIC/SSOP
AIN4
AIN3
AIN2
AIN1
NC
DB0
DB1
DB2
DB3
RD
1
2
3
4
5
6
24
23
22
21
ORDERING GUIDE
V
DD
NC
A0
A1
DB7
AIN6
1
AIN5
2
AIN4
3
28
27
26
25
24
AIN7
AIN8
V
DD
A0
A1
A2
Model
AD7824KN
AD7824LN
AD7824KR
AD7824BQ
AD7824CQ
AD7824TQ*
AD7824UQ*
AD7828KN
AD7828LN
AD7828KP
AD7828LP
AD7828BQ
AD7828CQ
AD7828BR
AD7828LRS
AD7828TQ*
AD7828UQ*
AD7828TE*
AD7828UE*
Temperature
Range
0°C to 70°C
0°C to 70°C
0°C to 70°C
–40°C to +85°C
–40°C to +85°C
–55°C to +125°C
–55°C to +125°C
0°C to 70°C
0°C to 70°C
0°C to 70°C
0°C to 70°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
0°C to 70°C
–55°C to +125°C
–55°C to +125°C
–55°C to +125°C
–55°C to +125°C
Total
Unadjusted Package
Error (LSBs) Option
±
1
±
1/2
±
1
±
1
±
1/2
±
1
±
1/2
±
1
±
1/2
±
1
±
1/2
±
1
±
1/2
+1
±
1/2
±
1
±
1/2
±
1
±
1/2
N-24
N-24
R-24
Q-24
Q-24
Q-24
Q-24
N-28
N-28
P-28A
P-28A
Q-28
Q-28
R-28
RS-28
Q-28
Q-28
E-28A
E-28A
AIN3
4
AIN2
5
AIN1
6
NC
7
AD7824
20
TOP VIEW
19
DB6
(Not to Scale)
18
DB5
7
8
9
10
17
16
15
14
13
AD7828
23
DB4
CS
RDY
V
REF
(+)
V
REF
(–)
TOP VIEW
22
DB7
(Not to Scale)
21
DB6
DB0
8
DB1
9
DB2
10
DB3
11
RD
12
INT
13
GND
14
20
19
18
17
16
15
DB5
DB4
CS
RDY
V
REF
(+)
V
REF
(–)
INT
11
GND
12
NC = NO CONNECT
NC = NO CONNECT
PLCC
AIN3
AIN4
AIN5
AIN6
AIN7
AIN8
V
DD
25
A0
24
A1
4
3
2
1
28 27 26
PIN 1
IDENTIFIER
AIN2
5
AIN1
6
NC
7
DB0
8
DB1
9
DB2
10
DB3
11
12 13 14 15
AD7828
TOP VIEW
(Not to Scale)
23
A2
22
DB7
21
DB6
20
DB5
*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.
LCCC
AIN3
AIN4
AIN5
AIN6
AIN7
AIN8
4
3
2
1
28 27 26
19
DB4
16
17
18
V
REF
(–)
V
REF
(+)
INT
GND
RD
RDY
CS
V
DD
25
A0
24
A1
23
A2
22
DB7
21
DB6
20
DB5
19
DB4
AIN2
5
AIN1
6
NC
7
NC = NO CONNECT
AD7828
TOP VIEW
(Not to Scale)
DB0
8
DB1
9
DB2
10
DB3
11
12 13 14 15 16 17 18
V
REF
(–)
V
REF
(+)
INT
GND
RD
NC = NO CONNECT
RDY
CS
–4–
REV. F
Typical Performance Characteristics–AD7824/AD7828
3
14
t
CRD
– CONVERSION TIME – s
13
I
DD
– SUPPLY CURRENT – mA
12
V
DD
= 5V
11
V
DD
= 5.25V
2
10
V
DD
= 5V
9
V
DD
= 4.75V
1
–100
8
–100
–50
0
50
100
T
A
– AMBIENT TEMPERATURE – C
150
–50
0
50
100
T
A
– AMBIENT TEMPERATURE – C
150
TPC 1. Conversion Time vs. Temperature
TPC 4. Power Supply Current vs. Temperature
(Not Including Reference Ladder)
2.0
V
DD
= 5V
T
A
= 25 C
2.0
V
DD
= 5V
V
REF
= 5V
T
A
= 25 C
LINEARITY ERROR – LSB*
1.0
LINEARITY ERROR – LSB
0
V
REF
256
1
2
V
REF
– V
3
4
5
1.5
1.5
1.0
0.5
0.5
0
0
300
400
500
600
700
800
900
*1LSB
=
t
P
– ns
TPC 2. Accuracy vs. V
REF
[V
REF
= V
REF
(+) – V
REF
(–)]
TPC 5. Accuracy vs. t
P
–36
–38
–40
–42
SNR – dB
–44
–46
–48
–50
–52
ENCODE RATE = 400kHz
INPUT SIGNAL = 5V p-p
MEASUREMENT BANDWIDTH = 80kHz
10
V
DD
= 5V
8
OUTPUT CURRENT – mA
I
SOURCE
, V
OUT
= 2.4V
6
4
I
SINK
, V
OUT
= 0.4V
2
1
2
3
4 5 7
10
20 30 40 50 70
INPUT FREQUENCY – kHz
100
0
–100
–50
0
50
100
T
A
– AMBIENT TEMPERATURE – C
150
TPC 3. Signal Noise Ratio vs. Input Frequency
TPC 6. Output Current vs. Temperature
REV. F
–5–
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