AD7768 Datasheet, PDF (44/99 Pages) Analog Devices – 8-/4-Channel, 24-Bit, Simultaneous Sampling ADCs with Power Scaling, 110.8 kHz BW

AD7768/AD7768-4
Data Sheet
APPLICATIONS INFORMATION
The AD7768/AD7768-4 offer users a multichannel platform
measurement solution for ac and dc signal processing.
Flexible filtering allows the AD7768/AD7768-4 to be config-
ured to simultaneously sample ac and dc signals on a per channel
basis. Power scaling allows users to trade off the input bandwidth
of the measurement vs. the current consumption. This ability,
coupled with the flexibility of the digital filtering, allows the
user to optimize the energy efficiency of the measurement,
while still meeting power, bandwidth, and performance targets.
Key capabilities that allow users to choose the AD7768/AD7768-4
as their platform high resolution ADC are highlighted as follows:
• Eight fully differential or pseudo differential analog inputs
on the AD7768 (four channels on the AD7768-4).
• Fast throughput simultaneous sampling ADCs catering for
input signals up to 110.8 kHz.
• Three selectable power modes (fast, median, and eco) for
scaling the current consumption and input bandwidth of
the ADC for optimal measurement efficiency.
• Analog input precharge and reference precharge buffers
reduce the drive requirements of external amplifiers.
• Control of reference and analog input precharge buffers on a
per channel basis.
• Wideband, low ripple, digital filter for ac measurement.
• Fast sinc5 filter for precision low frequency measurement.
• Two channel modes, defined by the user selected filter choice,
and decimation ratios, can be defined for use on different
ADC channels. This enables optimization of the input
bandwidth versus the signal of interest.
• Option of SPI or pin strapped control and configuration.
• Offset, gain, and phase calibration registers per channel.
• Common-mode voltage output buffer for use by driver
amplifier.
• On-board AVDD2 and IOVDD LDOs for the low power,
1.8 V, internal circuitry.
Refer to Figure 73 and Table 14 for the typical connections
and minimum requirements to get started using the
AD7768/AD7768-4.
Table 15 shows the typical power and performance of the
AD7768/AD7768-4 for the available power modes, for each
filter type.
SUGGESTED OP AMPS:
FAST MODE: ADA4896-2 OR ADA4807-2
MEDIAN MODE: ADA4940-2 OR ADA4807-2
ECO MODE: ADA4805-2
AVDD1A,
AVDD1B
VCM AD7768/AD7768-4
5V
AVDD2A,
AVDD2B
IOVDD
REGCAPA,
REGCAPB
DREGCAP
ADA4940-1/
ADA4940-2
AIN0+
AIN0–
AIN7+*
AIN7–*
PRECHARGE
BUFFERS
24-BIT
Σ-Δ
ADC
SINC5
LOW LATENCY FILTER
WIDEBAND
LOW RIPPLE FILTER
ADC
DATA
SERIAL
INTERFACE
SPI
CONTROL
INTERFACE
SYNC_IN
SYNC_OUT
START
RESET
FORMATx
DRDY
DCLK
DOUT0
DOUT1
DOUT2
DOUT3
DOUT4*
DOUT5*
DOUT6*, DIN
DOUT7*
ST0/CS
ST1*/SCLK
DEC0/SDO
DEC1/SDI
FILTER/GPIO4
AVSS
V_IN
–
V_IN
V_OUT
+
ADR4540
ADA4841-1
REFx– REFx+
XTAL2/MCLK
XTAL1
PIN/SPI MODE3/GPIO3
TO
MODE0/GPIO0
*THESE PINS EXIST ONLY ON THE AD7768.
Figure 73. Typical Connection Diagram
Rev. A | Page 44 of 99