AD7764_15 Datasheet, PDF (1/33 Pages) Analog Devices – 24-Bit, 312 kSPS, 109 dB Sigma-Delta ADC

24-Bit, 312 kSPS, 109 dB Sigma-Delta ADC
with On-Chip Buffers and Serial Interface
AD7764
FEATURES
High performance 24-bit ∑-∆ ADC
115 dB dynamic range at 78 kHz output data rate
109 dB dynamic range at 312 kHz output data rate
312 kHz maximum fully filtered output word rate
Pin-selectable oversampling rate (64×, 128×, and 256×)
Low power mode
Flexible SPI
Fully differential modulator input
On-chip differential amplifier for signal buffering
On-chip reference buffer
Full band low-pass finite impulse response (FIR) filter
Overrange alert pin
Digital gain correction registers
Power-down mode
Synchronization of multiple devices via SYNC pin
Daisy chaining
APPLICATIONS
Data acquisition systems
Vibration analysis
Instrumentation
FUNCTIONAL BLOCK DIAGRAM
V_OUTA– V_OUTA+ V_IN+ V_IN–
MCLK GND
V_INA+
V_INA–
DIFF
V_REF+
BUF
MULTIBIT
Σ-Δ
MODULATOR
RECONSTRUCTION
AV_DD1
AV_DD2
AV_DD3
AV_DD4
DV_DD
OVERRANGE
REFGND
SYNC
RESET/PWRDWN
INTERFACE LOGIC AND
OFFSET AND GAIN
CORRECTION REGISTERS
DECIMATION
FIR FILTER ENGINE
AD7764
FSO SCO SDI SDO FSI
Figure 1.
DEC_RATE
R_BIAS
Table 1. Related Devices
Part No. Description
AD7760 2.5 MSPS, 100 dB, parallel output on-chip buffers
AD7762 625 kSPS, 109 dB, parallel output on-chip buffers
AD7763 625 kSPS, 109 dB, serial output, on-chip buffers
AD7765 156 kSPS, 112 dB, serial output, on-chip buffers
AD7766 128/64/32 kSPS, 8.5 mW, 109 dB SNR
AD7767 128/64/32 kSPS, 8.5 mW, 109 dB SNR
GENERAL DESCRIPTION
The AD7764 is a high performance, 24-bit sigma-delta (Σ-Δ)
analog-to-digital converter (ADC). It combines wide input
bandwidth, high speed, and performance of 109 dB dynamic
range at a 312 kHz output data rate. With excellent dc
specifications, the converter is ideal for high speed data
acquisition of ac signals where dc data is also required.
Using the AD7764 eases the front-end antialias filtering
requirements, simplifying the design process significantly. The
AD7764 offers pin-selectable decimation rates of 64×, 128×,
and 256×. Other features include an integrated buffer to drive
the reference, as well as a fully differential amplifier to buffer
and level shift the input to the modulator.
An overrange alert pin indicates when an input signal has
exceeded the acceptable range. The addition of internal gain
and internal overrange registers makes the AD7764 a compact,
highly integrated data acquisition device requiring minimal
peripheral components.
The AD7764 also offers a low power mode, significantly
reducing power dissipation without reducing the output data
rate or available input bandwidth.
Rev. A
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The differential input is sampled at up to 40 MSPS by an analog
modulator. The modulator output is processed by a series of
low-pass filters. The external clock frequency applied to the
AD7764 determines the sample rate, filter corner frequencies,
and output word rate.
The AD7764 device boasts a full band on-board FIR filter. The
full stop-band attenuation of the filter is achieved at the Nyquist
frequency. This feature offers increased protection from signals
that lie above the Nyquist frequency being aliased back into the
input signal bandwidth.
The reference voltage supplied to the AD7764 determines the
input range. With a 4 V reference, the analog input range is
±3.2768 V differential, biased around a common mode of
2.048 V. This common-mode biasing can be achieved using
the on-chip differential amplifier, further reducing the external
signal conditioning requirements.
The AD7764 is available in a 28-lead TSSOP package and is
specified over the industrial temperature range of −40°C
to +85°C.
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