LC2MOS
a
12-Bit, 750 kHz/1 MHz, Sampling ADC
AD7886
FEATURES
FUNCTIONAL BLOCK DIAGRAM
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
V
DD
CS
RD CONVST
R3
R5
VIN1
CLOCK
10k
R4
3.5k
CONTROL
TIMER
BUSY
OSCILLATOR
AND TIMER
–
+
VIN2
Fast Bus Access Time—57 ns max
10k
T/H
+5REF
APPLICATIONS
4-BIT
LATCH
R1
9k
Digital Signal Processing
Speech Recognition and Synthesis
Spectrum Analysis
15
COMPARATORS
AND
SUM
DB11
DB0
R2
6.3k
THREE
STATE
OUTPUTS
4-BIT
LATCH
4-BIT FLASH
LOGIC
DSP Servo Control
V
REF
4-BIT
LATCH
4096
RESISTOR
DAC
SEGMENT SELECT
AD7886
AGND
V
DGND
SS
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.
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 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.
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.
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.
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.
3. Fast Microprocessor Interface.
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.
Standard control signals, CS and RD, and fast bus ac-
cess times make the AD7886 easy to interface to micro-
processors.
4. Low Power.
LC2MOS fabrication process gives low power dissipa-
tion of 250 mW.
*Contact your local salesperson for further information on the 1 MHz
version.
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
Fax: 617/326-8703
World Wide Web Site: http://www.analog.com
© Analog Devices, Inc., 1997