AD7886 Datasheet, PDF (1/16 Pages) Analog Devices – LC2MOS 12-Bit, 750 kHz/1 MHz, Sampling ADC

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LC²MOS
12-Bit, 750 kHz/1 MHz, Sampling ADC
AD7886
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
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.
FUNCTIONAL BLOCK DIAGRAM
VIN1
VIN2
+5REF
SUM
V_REF
AGND
V_DD
R3
R5
10k
R4
10k
R1
9k
3.5k
–
+
T/H
R2
6.3k
CLOCK
OSCILLATOR
AND TIMER
15
COMPARATORS
AND
4-BIT FLASH
LOGIC
4096
RESISTOR
DAC
SEGMENT SELECT
CS RD CONVST
CONTROL
TIMER
BUSY
4-BIT
LATCH
4-BIT
LATCH
4-BIT
LATCH
THREE
STATE
OUTPUTS
AD7886
DB11
DB0
V_{SS DGND}
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.
LC²MOS 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.
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© Analog Devices, Inc., 1997