AD7760 Datasheet, PDF (1/22 Pages) Analog Devices – 2.5 MSPS, 20-Bit ADC

Preliminary Technical Data
FEATURES
High performance 20-bit Sigma-Delta ADC
118dB SNR at 78kHz output data rate
100dB SNR at 2.5MHz output data rate
2.5 MHz maximum fully filtered output word rate
Programmable over-sampling rate (8x to 256x)
Flexible parallel interface
Fully differential modulator input
On-chip differential amplifier for signal buffering
Low pass FIR filter with default or user programmable
coefficients
Over-range alert bit
Digital offset and gain correction registers
Filter bypass modes
Low power and power down modes
Synchronization of multiple devices via SYNC pin
APPLICATIONS
Data acquisition systems
Vibration analysis
Instrumentation
PRODUCT OVERVIEW
The AD7760 high performance 20-bit sigma delta analog to
digital converter combines wide input bandwidth and high
speed with the benefits of sigma delta conversion with
performance of 100dB SNR at 2.5MSPS making it ideal for high
speed data acquisition. Wide dynamic range combined with
significantly reduced anti-aliasing requirements simplify the
design process. An integrated buffer to drive the reference, a
differential amplifier for signal buffering and level shifting, an
over-range flag, internal gain & offset registers and a low-pass
digital FIR filter make the AD7760 a compact highly integrated
data acquisition device requiring minimal peripheral
component selection. In addition the device offers
programmable decimation rates and the digital FIR filter can be
adjusted if the default characteristics are not appropriate to the
application. The AD7760 is ideal for applications demanding
high SNR without necessitating design of complex front end
signal processing.
2.5 MSPS, 20-Bit Σ∆ ADC
AD7760
FUNCTIONAL BLOCK DIAGRAM
VIN- VIN+
DIFF
VREF+
+
BUF
-
MCLK
MCLK
SYNC
RESET
AD7760
Control Logic,
I/O and
Registers
Multi-Bit
Sigma-Delta
Modulator
Reconstruction
Programmable
Decimation
FIR Filter
Engine
AVDD1
AVDD2
AVDD3
AVDD4
DECAP
RBIAS
AGND
VDRIVE
DVDD
DGND
DB0 - DB15
Figure 1.
The differential input is sampled at up to 40MS/s by an analog
modulator. The modulator output is processed by a series of
low-pass filters, the final one having default or user
programmable coefficients. The sample rate, filter corner
frequencies and output word rate are set by a combination of
the external clock frequency and the configuration registers of
the AD7760.
The reference voltage supplied to the AD7760 determines the
analog input range. With a 4V reference, the analog input range
is ±3.2V differential biased around a common mode of 2V. This
common mode biasing can be achieved using the on-chip
differential amplifiers, further reducing the external signal
conditioning requirements.
The AD7760 is available in an exposed paddle 64-lead TQFP
and 48-lead CSP packages and is specified over the industrial
temperature range from -40°C to +85°C.
Rev. PrN
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