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AD7866
Dual 1 MSPS, 12-Bit, 2-Channel
SAR ADC with Serial Interface
FEATURES
Dual 12-Bit, 2-Channel ADC
Fast Throughput Rate: 1 MSPS
Specified for V
DD
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
70 dB SNR at 300 kHz Input Frequency
On-Board Reference 2.5 V
–40ⴗC to +125ⴗC Operation
Flexible Power/Throughput Rate Management
Simultaneous Conversion/Read
No Pipeline Delays
High Speed Serial Interface SPI
TM
/QSPI
TM
/
MICROWIRE
TM
/DSP Compatible
Shutdown Mode: 1 A Max
20-Lead TSSOP Package
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/H
MUX
BUF
OUTPUT
DRIVERS
RANGE
SCLK
CS
CONTROL
LOGIC
V
B2
V
B1
D
OUT
B
12-BIT
SUCCESSIVE
APPROXIMATION
ADC
T/H
MUX
OUTPUT
DRIVERS
BUF
D
CAP
AAV
DD
DV
DD
D
CAP
B
AGND AGND
V
DRIVE
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-and-hold amplifier that 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; 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
twos complement output coding. The AD7866 has an on-chip
2.5 V reference that 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 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 conver-
sion 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.
