Dual 1 MSPS, 12-Bit, 2-Channel
SAR ADC with Serial Interface
a
AD7866
FEATURES
FUNCTIONAL BLOCK DIAGRAM
Dual 12-Bit, 2-Channel ADC
Fast Throughput Rate
V
D
A
AV
DV
DD
REF
CAP
REF SELECT
DD
1 MSPS
Specified for VDD of 2.7 V to 5.25 V
Low Power
11.4 mW Max at 1 MSPS with 3 V Supplies
24 mW Max at 1 MSPS with 5 V Supplies
Wide Input Bandwidth
2.5V
REF
BUF
AD7866
12-BIT
SUCCESSIVE-
APPROXIMATION
ADC
V
A1
OUTPUT
DRIVERS
D
A
T/H
OUT
MUX
V
A2
70 dB SNR at 300 kHz Input Frequency
Onboard Reference 2.5 V
Flexible Power/Throughput Rate Management
Simultaneous Conversion/Read
No Pipeline Delays
A0
RANGE
SCLK
CS
CONTROL
LOGIC
V
DRIVE
12-BIT
SUCCESSIVE-
APPROXIMATION
ADC
High-Speed Serial Interface SPITM/QSPITM
MICROWIRETM/DSP Compatible
Shut-Down Mode
/
V
B1
OUTPUT
DRIVERS
D
B
T/H
OUT
MUX
V
B2
1 A Max
BUF
20-Lead TSSOP Package
D
B
AGND AGND
DGND
CAP
GENERAL DESCRIPTION
reference is preferred. Each on-board ADC can also be supplied
with a separate individual external reference.
The AD7866 is a dual 12-bit high-speed, low power, successive-
approximation ADC. The part operates from a single 2.7 V to 5.25 V
power supply and features throughput rates up to 1 MSPS. The
device contains two ADCs, each preceded by a low-noise, wide
bandwidth track/hold amplifier which can handle input frequencies
in excess of 10 MHz.
The AD7866 is available in a 20-lead thin shrink small outline
(TSSOP) package.
PRODUCT HIGHLIGHTS
1. The AD7866 features two complete ADC functions allowing
simultaneous sampling and conversion of two channels. Each
ADC has a 2-channel input multiplexer. The conversion
result of both channels is available simultaneously on separate
data lines, or both may be taken on one data line if only one
serial port is available.
The conversion process and data acquisition are controlled
using standard control inputs allowing easy interfacing to
microprocessors or DSPs. The input signal is sampled on the
falling edge of CS and conversion is also initiated at this point.
The conversion time is determined by the SCLK frequency.
There are no pipelined delays associated with the part.
2. High Throughput with Low Power Consumption—The
AD7866 offers a 1 MSPS throughput rate with 11.4 mW
maximum power consumption when operating at 3 V.
The AD7866 uses advanced design techniques to achieve very low
power dissipation at high throughput rates. With 3 V supplies
and 1 MSPS throughput rate, the part consumes a maximum of
3.8 mA. With 5 V supplies and 1 MSPS, the current consumption
is a maximum of 4.8 mA. The part also offers flexible power/
throughput rate management when operating in sleep mode.
3. Flexible Power/Throughput Rate Management—The
conversion rate is determined by the serial clock allowing
the power consumption to be reduced as the conversion time
is reduced through a SCLK frequency increase. Power
efficiency can be maximized at lower throughput rates if the
part enters sleep during conversions.
The analog input range for the part can be selected to be a 0 V
to VREF range or a 2 × VREF range with either straight binary or
two’s complement output coding. The AD7866 has an
on-chip 2.5 V reference which can be overdriven if an external
4. No Pipeline Delay—The part features two standard successive-
approximation ADCs with accurate control of the sampling
instant via a CS input and once off conversion control.
SPI and QSPI are trademarks of Motorola Inc.
MICROWIRE is a trademark of National Semiconductor Corporation.
REV. 0
Information furnished by Analog Devices is believed to be accurate and
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
under any patent or patent rights of Analog Devices.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700
Fax: 781/326-8703
www.analog.com
© Analog Devices, Inc., 2002
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