a LC2MOS 4-Channel, 12-Bit Simultaneous
Sampling Data Acquisition System
Four On-Chip Track/Hold Amplifiers
Simultaneous Sampling of 4 Channels
Fast 12-Bit ADC with 8 s Conversion Time/Channel
29 kHz Sample Rate for All Four Channels
؎10 V Input Range
؎5 V Supplies
Digital Signal Processing
The AD7874 is a four-channel simultaneous sampling, 12-bit
data acquisition system. The part contains a high speed 12-bit
ADC, on-chip reference, on-chip clock and four track/hold am-
plifiers. This latter feature allows the four input channels to be
sampled simultaneously, thus preserving the relative phase
information of the four input channels, which is not possible if
all four channels share a single track/hold amplifier. This makes
the AD7874 ideal for applications such as phased-array sonar
and ac motor controllers where the relative phase information is
The aperture delay of the four track/hold amplifiers is small and
specified with minimum and maximum limits. This allows sev-
eral AD7874s to sample multiple input channels simultaneously
without incurring phase errors between signals connected to
several devices. A reference output/reference input facility also
allows several AD7874s to be driven from the same reference
In addition to the traditional dc accuracy specifications such as
linearity, full-scale and offset errors, the AD7874 is also fully
specified for dynamic performance parameters including distor-
tion and signal-to-noise ratio.
The AD7874 is fabricated in Analog Devices’ Linear Compat-
ible CMOS (LC2MOS) process, a mixed technology process
that combines precision bipolar circuits with low-power CMOS
logic. The part is available in a 28-pin, 0.6" wide, plastic or her-
metic dual-in-line package (DIP), in a 28-terminal leadless ce-
ramic chip carrier (LCCC) and in a 28-pin SOIC.
FUNCTIONAL BLOCK DIAGRAM
INT CS RD CONVST VDD VDD
AGND DGND VSS
1. Simultaneous Sampling of Four Input Channels.
Four input channels, each with its own track/hold amplifier,
allow simultaneous sampling of input signals. Track/hold ac-
quisition time is 2 µs, and the conversion time per channel is
8 µs, allowing 29 kHz sample rate for all four channels.
2. Tight Aperture Delay Matching.
The aperture delay for each channel is small and the aperture
delay matching between the four channels is less than 4 ns.
Additionally, the aperture delay specification has upper and
lower limits allowing multiple AD7874s to sample more than
3. Fast Microprocessor Interface.
The high speed digital interface of the AD7874 allows direct
connection to all modern 16-bit microprocessors and digital
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
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