LC2MOS
a
16-Bit, High-Speed Sampling ADCs
AD7884/AD7885
FUNCTIONAL BLOCK DIAGRAMS
FEATURES
Monolithic Construction
Fast Conversion: 5.3 s
High Throughput: 166 kSPS
Low Power: 250 mW
V
SS
V
SS
؎3V
F ؎3V S
IN
AGNDS AGNDF AV AV
DD
IN
DD
R3
C1
3k⍀
R2
3k⍀
؎5V
؎5V
S
IN
AD7884
APPLICATIONS
A1
F
R1
SW1
IN
5k⍀
Automatic Test Equipment
Medical Instrumentation
Industrial Control
Data Acquisition Systems
Robotics
D
R
I
O
U
9-BIT
ADC
DB15
DB0
9
LATCH
SW2
R4
T
P
U
T
V
E
R
S
R5
4k⍀
16
16
4k⍀
+
R6
ALU
2k⍀
9
V
REF–
A2
SW3
16-BIT
9
ACCURATE
DAC
CONTROL
TIMER
CS
RD
R7
2k⍀
GENERAL DESCRIPTION
The AD7884/AD7885 is a 16-bit monolithic analog-to-digital
converter with internal sample-and-hold and a conversion time
of 5.3 µs. The maximum throughput rate is 166 kSPS. It uses a
two-pass flash architecture to achieve this speed. Two input
ranges are available: 5 V and 3 V. Conversion is initiated by
the CONVST signal. The result can be read into a microprocessor
using the CS and RD inputs on the device. The AD7884 has a
16-bit parallel reading structure while the AD7885 has a byte reading
structure. The conversion result is in two’s complement code.
R8
2k⍀
V
F
V
S V
V
REF–
CONVST BUSY DGND
GND
REF+
REF+
INV
V
V
SS
؎3V
AGNDS AGNDF AV AV
DD SS
DD
IN
R3
R2
C1
3k⍀
3k⍀
؎5V
؎5V
S
IN
AD7885
A1
F
R1
SW1
IN
5k⍀
The AD7884/AD7885 has its own internal oscillator which controls
conversion. It runs from 5 V supplies and needs a VREF+ of 3 V.
D
R
I
O
U
9-BIT
ADC
DB7
DB0
9
The AD7884 is available in a 40-lead Cerdip package and in a
44-lead PLCC package.
LATCH
+
ALU
SW2
R4
4k⍀
T
P
U
T
V
E
R
S
R5
4k⍀
8
16
R6
2k⍀
9
V
REF–
The AD7885 is available in a 28-lead Cerdip package and the AD7885A
is available in a 44-lead PLCC package.
A2
SW3
16-BIT
9
ACCURATE
DAC
CONTROL
TIMER
CS
RD
R7
2k⍀
HBEN
R8
2k⍀
V
F
V
S V
V
REF–
CONVST BUSY DGND
GND
REF+
REF+
INV
REV. D
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reliable. However, no responsibility is assumed by Analog Devices for its
use, norforanyinfringementsofpatentsorotherrightsofthirdpartiesthat
may result from its use. No license is granted by implication or otherwise
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© Analog Devices, Inc., 2002