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AD7825_15

3 V/5 V, 2 MSPS, 8-Bit, 1-/4-/8-Channel Sampling ADCs

厂商名称:ADI(亚德诺半导体)

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3 V/5 V, 2 MSPS, 8-Bit, 1-/4-/8-Channel
Sampling ADCs
AD7822/AD7825/AD7829
FEATURES
8-bit half-flash ADC with 420 ns conversion time
One, four, and eight single-ended analog input channels
Available with input offset adjust
On-chip track-and-hold
SNR performance given for input frequencies up to 10 MHz
On-chip reference (2.5 V)
Automatic power-down at the end of conversion
Wide operating supply range
3 V ± 10% and 5 V ± 10%
Input ranges
0 V to 2 V p-p, V
DD
= 3 V ± 10%
0 V to 2.5 V p-p, V
DD
= 5 V ± 10%
Flexible parallel interface with EOC pulse to allow
standalone operation
FUNCTIONAL BLOCK DIAGRAM
CONVST EOC A0
1
A1
1
A2
2
PD
3
V
DD
CONTROL
LOGIC
COMP
2.5V
REF
V
IN1
V
IN24
V
IN34
V
IN44
V
IN55
V
IN65
V
IN75
V
IN85
BUF
INPUT
MUX
T/H
8-BIT
HALF
FLASH
ADC
V
REF IN/OUT
PARALLEL
PORT
DB7
DB0
V
MID
1
A0, A1
2
A2
3
PD
4
V
IN2
TO V
IN4
5
V
IN5
TO V
IN8
AGND
DGND
CS RD
APPLICATIONS
Data acquisition systems, DSP front ends
Disk drives
Mobile communication systems, subsampling
applications
Figure 1.
GENERAL DESCRIPTION
The AD7822/AD7825/AD7829 are high speed, 1-, 4-, and
8-channel, microprocessor-compatible, 8-bit analog-to-digital
converters with a maximum throughput of 2 MSPS. The AD7822/
AD7825/AD7829 contain an on-chip reference of 2.5 V
(2% tolerance); a track-and-hold amplifier; a 420 ns, 8-bit half-
flash ADC; and a high speed parallel interface. The converters
can operate from a single 3 V ± 10% and 5 V ± 10% supply.
The AD7822/AD7825/AD7829 combine the convert start and
power-down functions at one pin, that is, the CONVST pin.
This allows a unique automatic power-down at the end of a
conversion to be implemented. The logic level on the CONVST
pin is sampled after the end of a conversion when an EOC (end
of conversion) signal goes high. If it is logic low at that point,
the ADC is powered down. The AD7822 and AD7825 also have
a separate power-down pin (see the Operating Modes section).
The parallel interface is designed to allow easy interfacing to
microprocessors and DSPs. Using only address decoding logic,
the parts are easily mapped into the microprocessor address
space. The EOC pulse allows the ADCs to be used in a stand-
alone manner (see the Parallel Interface section.)
The AD7822 and AD7825 are available in 20-lead and 24-lead,
0.3" wide, plastic dual in-line packages (PDIP); 20-lead and
24-lead standard small outline packages (SOIC); and 20-lead
and 24-lead thin shrink small outline packages (TSSOP). The
AD7829 is available in a 28-lead, 0.6" wide PDIP; a 28-lead
SOIC; and a 28-lead TSSOP.
PRODUCT HIGHLIGHTS
1.
Fast Conversion Time. The AD7822/AD7825/AD7829
have a conversion time of 420 ns. Faster conversion times
maximize the DSP processing time in a real-time system.
Analog Input Span Adjustment. The V
MID
pin allows the
user to offset the input span. This feature can reduce the
requirements of single-supply op amps and take into
account any system offsets.
FPBW (Full Power Bandwidth) of Track-and-Hold.
The track-and-hold amplifier has an excellent high
frequency performance. The AD7822/AD7825/AD7829
are capable of converting full-scale input signals up to a
frequency of 10 MHz. This makes the parts ideally suited
to subsampling applications.
Channel Selection. Channel selection is made without the
necessity of writing to the part.
2.
3.
4.
Rev. C
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. Specifications subject to change without notice. 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.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
www.analog.com
Fax: 781.461.3113
©2006 Analog Devices, Inc. All rights reserved.
01321-001
AD7825/AD7829
AD7829
AD7822/AD7825
AD7825/AD7829
AD7829
AD7822/AD7825/AD7829
TABLE OF CONTENTS
Features .............................................................................................. 1
Applications....................................................................................... 1
General Description ......................................................................... 1
Functional Block Diagram .............................................................. 1
Product Highlights ....................................................................... 1
Revision History ............................................................................... 2
Specifications..................................................................................... 3
Timing Characteristics ................................................................ 5
Timing Diagram ........................................................................... 5
Absolute Maximum Ratings............................................................ 6
ESD Caution.................................................................................. 6
Pin Configurations and Function Descriptions ........................... 7
Terminology ...................................................................................... 8
Circuit Information ........................................................................ 10
Circuit Description..................................................................... 10
Typical Connection Diagram ................................................... 10
ADC Transfer Function............................................................. 11
Analog Input ............................................................................... 11
Power-Up Times......................................................................... 14
Power vs. Throughput................................................................ 15
Operating Modes........................................................................ 15
Parallel Interface......................................................................... 17
Microprocessor Interfacing........................................................... 18
AD7822/AD7825/AD7829 to 8051 ......................................... 18
AD7822/AD7825/AD7829 to PIC16C6x/PIC16C7x................ 18
AD7822/AD7825/AD7829 to ADSP-21xx ............................. 18
Interfacing Multiplexer Address Inputs .................................. 18
AD7822 Standalone Operation ................................................ 19
Outline Dimensions ....................................................................... 20
Ordering Guide .......................................................................... 25
REVISION HISTORY
8/06—Rev. B to Rev. C
Changes to General Description .................................................... 1
Changes to Table 1............................................................................ 3
Changes to Typical Connection Diagram Section ..................... 10
Updated Outline Dimensions ....................................................... 20
Changes to Ordering Guide .......................................................... 25
10/01—Rev. A to Rev. B
Changes to Power Requirements.................................................... 3
Changes to Pin Function Description ........................................... 5
Changes to Circuit Description ...................................................... 7
Changes to Typical Connection Diagram Section........................7
Changes to Analog Input Section....................................................8
Changes to Analog Input Selection Section...................................9
Changes to Power-Up Times Section .......................................... 10
Changes to Power vs. Throughput Section ................................. 11
Added AD7822 Stand-Alone Operation section ....................... 15
12/99—Rev.
0 to Rev. A
Rev. C | Page 2 of 28
AD7822/AD7825/AD7829
SPECIFICATIONS
V
DD
= 3 V ± 10%, V
DD
= 5 V ± 10%, GND = 0 V, V
REF IN/OUT
= 2.5 V. All specifications −40°C to +85°C, unless otherwise noted.
Table 1.
Parameter
DYNAMIC PERFORMANCE
Signal to (Noise + Distortion) Ratio
1
Total Harmonic Distortion
1
Peak Harmonic or Spurious Noise
1
Intermodulation Distortion
1
Second-Order Terms
Third-Order Terms
Channel-to-Channel Isolation
1
DC ACCURACY
Resolution
Minimum Resolution for Which
No Missing Codes Are Guaranteed
Integral Nonlinearity (INL)
1
Differential Nonlinearity (DNL)
1
Gain Error
1
Gain Error Match
1
Offset Error
1
Offset Error Match
1
ANALOG INPUTS
2
V
DD
= 5 V ± 10%
V
IN1
to V
IN8
Input Voltage
V
MID
Input Voltage
V
DD
= 3 V ± 10%
V
IN1
to V
IN8
Input Voltage
V
MID
Input Voltage
V
IN
Input Leakage Current
V
IN
Input Capacitance
V
MID
Input Impedance
REFERENCE INPUT
V
REF IN/OUT
Input Voltage Range
Input Current
ON-CHIP REFERENCE
Reference Error
Temperature Coefficient
LOGIC INPUTS
Input High Voltage, V
INH
Input Low Voltage, V
INL
Input High Voltage, V
INH
Input Low Voltage, V
INL
Input Current, I
IN
Input Capacitance, C
IN
Version B
48
−55
−55
−65
−65
−70
8
8
±0.75
±0.75
±2
±0.1
±1
±0.1
Unit
dB min
dB max
dB max
fa = 27.3 kHz, fb = 28.3 kHz
dB typ
dB typ
dB typ
Bits
Bits
LSB max
LSB max
LSB max
LSB typ
LSB max
LSB typ
See Analog Input section
Input voltage span = 2.5 V
V
DD
0
V
DD
− 1.25
1.25
V
DD
0
V
DD
− 1
1
±1
15
6
2.55
2.45
1
100
±50
50
2.4
0.8
2
0.4
±1
10
V max
V min
V max
V min
V max
V min
V max
V min
μA max
pF max
kΩ typ
V max
V min
μA typ
μA max
mV max
ppm/°C typ
V min
V max
V min
V max
μA max
pF max
V
DD
= 5 V ± 10%
V
DD
= 5 V ± 10%
V
DD
= 3 V ± 10%
V
DD
= 3 V ± 10%
10 nA typical, V
IN
= 0 V to V
DD
Test Condition/Comment
f
IN
= 30 kHz, f
SAMPLE
= 2 MHz
f
IN
= 20 kHz
Default V
MID
= 1.25 V
Input voltage span = 2 V
Default V
MID
= 1 V
2.5 V + 2%
2.5 V − 2%
Nominal 2.5 V
Rev. C | Page 3 of 28
AD7822/AD7825/AD7829
Parameter
LOGIC OUTPUTS
Output High Voltage, V
OH
Version B
Unit
Test Condition/Comment
I
SOURCE
= 200 μA
V
DD
= 5 V ± 10%
V
DD
= 3 V ± 10%
I
SINK
= 200 μA
V
DD
= 5 V ± 10%
V
DD
= 3 V ± 10%
4
2.4
Output Low Voltage, V
OL
0.4
0.2
±1
10
200
420
±1
4.5
5.5
2.7
3.3
12
5
0.2
36
9.58
23.94
V min
V min
V max
V max
μA max
pF max
ns max
ns max
LSB max
V min
V max
V min
V max
mA max
μA max
μA typ
mW max
mW typ
mW typ
High Impedance Leakage Current
High Impedance Capacitance
CONVERSION RATE
Track-and-Hold Acquisition Time
Conversion Time
POWER SUPPLY REJECTION
V
DD
± 10%
POWER REQUIREMENTS
V
DD
V
DD
I
DD
Normal Operation
Power-Down
Power Dissipation
Normal Operation
Power-Down
200 kSPS
500 kSPS
1
2
See Circuit Description section
5 V ± 10%; for specified performance
3 V ± 10%; for specified performance
8 mA typical
Logic inputs = 0 V or V
DD
V
DD
= 3 V
24 mW typical
See the Terminology section of this data sheet.
Refer to the Analog Input section for an explanation of the analog input(s).
Rev. C | Page 4 of 28
AD7822/AD7825/AD7829
TIMING CHARACTERISTICS
V
REF IN/OUT
= 2.5 V. All specifications −40°C to +85°C, unless otherwise noted.
Table 2.
Parameter
1,
2
t
1
t
2
t
3
t
4
t
5
t
6
t
7
t
8
t
9 3
t
10 4
t
11
t
12
t
13
t
POWER UP
t
POWER UP
1
2
5 V
±
10%
420
20
30
110
70
10
0
0
30
10
5
20
10
15
200
25
1
3 V
±
10%
420
20
30
110
70
10
0
0
30
20
5
20
10
15
200
25
1
Unit
ns max
ns min
ns min
ns max
ns min
ns max
ns min
ns min
ns min
ns max
ns min
ns max
ns min
ns min
ns min
μs typ
μs max
Conditions/Comments
Conversion time
Minimum CONVST pulse width
Minimum time between the rising edge of RD and the next falling edge of convert star
EOC pulse width
RD rising edge to EOC pulse high
CS to RD setup time
CS to RD hold time
Minimum RD pulse width
Data access time after RD low
Bus relinquish time after RD high
Address setup time before falling edge of RD
Address hold time after falling edge of RD
Minimum time between new channel selection and convert start
Power-up time from rising edge of CONVST using on-chip reference
Power-up time from rising edge of CONVST using external 2.5 V reference
Sample tested to ensure compliance.
See Figure 24, Figure 25, and Figure 26.
3
Measured with the load circuit of Figure 2 and defined as the time required for an output to cross 0.8 V or 2.4 V with V
DD
= 5 V ± 10%, and time required for an output
to cross 0.4 V or 2.0 V with V
DD
= 3 V ± 10%.
4
Derived from the measured time taken by the data outputs to change 0.5 V when loaded with the circuit of Figure 2. The measured number is then extrapolated back
to remove the effects of charging or discharging the 50 pF capacitor. This means that the time, t
10
, quoted in the timing characteristics is the true bus relinquish time
of the part and, as such, is independent of external bus loading capacitances.
TIMING DIAGRAM
200µA
I
OL
TO OUTPUT
PIN
2.1V
C
L
50pF
200µA
I
OH
01321-002
Figure 2. Load Circuit for Access Time and Bus Relinquish Time
Rev. C | Page 5 of 28
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参数对比
与AD7825_15相近的元器件有:AD7829_15、AD7822_15。描述及对比如下:
型号 AD7825_15 AD7829_15 AD7822_15
描述 3 V/5 V, 2 MSPS, 8-Bit, 1-/4-/8-Channel Sampling ADCs 3 V/5 V, 2 MSPS, 8-Bit, 1-/4-/8-Channel Sampling ADCs 3 V/5 V, 2 MSPS, 8-Bit, 1-/4-/8-Channel Sampling ADCs
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