a
FEATURES
750 kHz/1 MHz Throughput Rate
1 s/750 ns Conversion Time
12-Bit No Missed Codes Over Temperature
67 dB SNR at 100 kHz Input Frequency
Low Power—250 mW typ
Fast Bus Access Time—57 ns max
APPLICATIONS
Digital Signal Processing
Speech Recognition and Synthesis
Spectrum Analysis
DSP Servo Control
LC
2
MOS
12-Bit, 750 kHz/1 MHz, Sampling ADC
AD7886
FUNCTIONAL BLOCK DIAGRAM
V
DD
R3
VIN1
10k
R4
VIN2
10k
+5REF
R1
9k
SUM
R2
6.3k
V
REF
4096
RESISTOR
DAC
AGND
–
+
T/H
3.5k
R5
CLOCK
OSCILLATOR
AND TIMER
CONTROL
TIMER
BUSY
CS
RD CONVST
4-BIT
LATCH
15
COMPARATORS
AND
4-BIT FLASH
LOGIC
DB11
4-BIT
LATCH
THREE
STATE
OUTPUTS
DB0
4-BIT
LATCH
SEGMENT SELECT
AD7886
V
SS
DGND
GENERAL DESCRIPTION
The AD7886 is a 12-bit ADC with a sample-and-hold amplifier
offering high speed performance combined with low power dissi-
pation. The AD7886 is a triple pass flash ADC that uses 15
comparators in a 4-bit flash technique to achieve 12-bit accuracy
in 1
µs/750
ns conversion time. An on-chip clock oscillator pro-
vides the appropriate timing for each of the three conversion
stages, eliminating the need for any external clocks. Acquisition
time of the sample-and-hold amplifier gives a resulting through-
put rate of 750 kHz/1 MHz.*
The AD7886 operates from
±
5 V power supplies. Pin-strappable
inputs offer a choice of three analog input ranges: 0 V to 5 V,
0 V to 10 V or
±
5 V.
In addition to the traditional dc accuracy specifications such as
linearity, offset and full-scale errors, the AD7886 is also speci-
fied for dynamic performance parameters, including harmonic
distortion and signal-to-noise ratio.
The AD7886 has a high speed digital interface with three-state
data outputs. Conversion control is provided by a
CONVST
in-
put. Data access is controlled by
CS
and
RD
inputs, standard
microprocessor signals. The data access time of less than 57 ns
means that the AD7886 can interface directly to most modern
microprocessors, including DSP processors.
*Contact your local salesperson for further information on the 1 MHz
version.
The AD7886 is fabricated in Analog Devices’ Linear Com-
patible CMOS process, a mixed technology process that
combines precision bipolar circuits with low power CMOS
logic.
The AD7886 is available in both a 28-pin DIP and a 28-pin
leaded chip carrier.
PRODUCT HIGHLIGHTS
1. Fast 1.33
µs/1 µs
Throughput Time.
Fast throughput time makes the AD7886 suitable for a
wide range of data acquisition applications.
2. Dynamic Specifications for DSP Users.
The AD7886 is specified for ac parameters, including
signal-to-noise ratio, harmonic distortion and inter-
modulation distortion. Key digital timing parameters are
also tested and guaranteed over the full operating tem-
perature range.
3. Fast Microprocessor Interface.
Standard control signals,
CS
and
RD,
and fast bus ac-
cess times make the AD7886 easy to interface to micro-
processors.
4. Low Power.
LC
2
MOS fabrication process gives low power dissipa-
tion of 250 mW.
REV. B
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
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 617/329-4700
World Wide Web Site: http://www.analog.com
Fax: 617/326-8703
© Analog Devices, Inc., 1997
AD [ ANALOG DEVICES ]
