2
LC MOS
a
16-Bit, High Speed Sampling ADCs
AD7884/AD7885
FEATURES
FUNCTIO NAL BLO CK D IAGRAMS
Monolithic Construction
Fast Conversion: 5.3 s
High Throughput: 166 kSPS
Low Pow er: 250 m W
V
V
SS
±3V
IN
F
±3V
S
AV
SS
AV
DD
AGNDS AGNDF
DD
IN
R3
3kΩ
AD7884
R2
3kΩ
C1
A1
±5V
±5V
S
F
IN
APPLICATIONS
R1
SW1
IN
5kΩ
Autom atic Test Equipm ent
Medical Instrum entation
Industrial Control
D
O
R4 4kΩ
R
I
DB15
DB0
9-BIT
ADC
U
T
P
U
T
9
9
SW2
LATCH
V
E
R
S
R5
4kΩ
R6
2kΩ
Data Acquisition System s
Robotics
+
16
16
ALU
V
REF–
A2
SW3
16-BIT
9
ACCURATE
DAC
CS
RD
TIMER
CONTROL
R7
2kΩ
GENERAL D ESCRIP TIO N
T he AD7884/AD7885 is a 16-bit monolithic analog-to-digital
converter with internal sample-and-hold and a conversion time
of 5.3 µs. T he maximum throughput rate is 166 kSPS. It uses a
two pass flash architecture to achieve this speed. T wo input
ranges are available: ±5 V and ±3 V. Conversion is initiated by
the CONVST signal. T he result can be read into a microproces-
sor using the CS and RD inputs on the device. T he AD7884 has
a 16-bit parallel reading structure while the AD7885 has a byte
reading structure. T he conversion result is in 2s complement
code.
R8
2kΩ
V
V
V
F
V
S
INV
REF–
GND
DGND
V
REF+
REF+
CONVST BUSY
±3V
AGNDS AGNDF
IN
V
DD
AV
AV
SS
SS
DD
R3 3kΩ
R2
AD7885
3kΩ
C1
A1
±5V
±5V
S
F
IN
IN
R1
5kΩ
SW1
D
O
T he AD7884/AD7885 has its own internal oscillator which con-
trols conversion. It runs from ±5 V supplies and needs a VREF+
of +3 V.
R4 4kΩ
R
I
DB7
DB0
U
T
P
U
T
9-BIT
ADC
9
9
SW2
LATCH
V
E
R
S
R5
4kΩ
R6
2kΩ
+
8
16
ALU
V
REF–
T he AD7884 is available in a 40-pin plastic DIP package and in
a 44-pin PLCC package.
A2
SW3
16-BIT
9
T he AD7885 is available in a 28-pin plastic DIP package and
the AD7885A is available in a 44-pin PLCC package.
ACCURATE
DAC
CS
RD
CONTROL
TIMER
HBEN
R7
2kΩ
R8
2kΩ
V
F
V
S
V
INV
V
REF–
DGND
GND
REF+
REF+
CONVST BUSY
REV. C
Inform ation furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assum ed by Analog Devices for its
use, nor for any infringem ents of patents or other rights of third parties
which m ay result from its use. No license is granted by im plication or
otherwise under any patent or patent rights of Analog Devices.
© Analog Devices, Inc., 1995
One Technology Way, P.O. Box 9106, Norw ood, MA 02062-9106, U.S.A.
Tel: 617/ 329-4700 Fax: 617/ 326-8703