REV.0
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a
AD7866
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700 www.analog.com
Fax: 781/326-8703 © Analog Devices, Inc., 2002
Dual 1 MSPS, 12-Bit, 2-Channel
SAR ADC with Serial Interface
FUNCTIONAL BLOCK DIAGRAM
V
A2
V
A1
DGND
D
OUT
A
REF SELECT
V
REF
A0
12-BIT
SUCCESSIVE-
APPROXIMATION
ADC
AD7866
2.5V
REF
T/HMUX
BUF
OUTPUT
DRIVERS
RANGE
SCLK
CS
CONTROL
LOGIC
V
B2
V
B1
D
OUT
B
12-BIT
SUCCESSIVE-
APPROXIMATION
ADC
T/HMUX
OUTPUT
DRIVERS
BUF
D
CAP
AAV
DD
DV
DD
D
CAP
BAGND AGND
V
DRIVE
FEATURES
Dual 12-Bit, 2-Channel ADC
Fast Throughput Rate
1 MSPS
Specified for V
DD
of 2.7V to 5.25V
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
70 dB SNR at 300 kHz Input Frequency
Onboard Reference 2.5 V
Flexible Power/Throughput Rate Management
Simultaneous Conversion/Read
No Pipeline Delays
High-Speed Serial Interface SPI
TM
/QSPI
TM
/
MICROWIRE
TM
/DSP Compatible
Shut-Down Mode
1 H9262A Max
20-Lead TSSOP Package
GENERAL DESCRIPTION
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 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.
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.
The analog input range for the part can be selected to be a 0 V
to V
REF
range or a 2 × V
REF
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
reference is preferred. Each on-board ADC can also be supplied
with a separate individual external reference.
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.
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.
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.
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.