LC2MOS 4-Channel, 12-Bit Simultaneous Sampling Data Acquisition System AD7874
FEATURES 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 On-Chip Reference ؎10 V Input Range ؎5 V Supplies APPLICATIONS Sonar Motor Controllers Adaptive Filters Digital Signal Processing
FUNCTIONAL BLOCK DIAGRAM INT
TRACK/ HOLD 1
TRACK/ HOLD 2
TRACK/ HOLD 3
CONTROL LOGIC VIN1
TRACK/ HOLD 4
REFERENCE BUFFER 12-BIT DAC
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 amplifiers. 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 important.
The aperture delay of the four track/hold amplifiers is small and specified with minimum and maximum limits. This allows several 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 source.
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 four channels.
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 distortion and signal-to-noise ratio.
3V REFERENCE AGND DGND
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 acquisition time is 2 µs, and the conversion time per channel is 8 µs, allowing 29 kHz sample rate for all four channels.
3. Fast Microprocessor Interface. The high speed digital interface of the AD7874 allows direct connection to all modern 16-bit microprocessors and digital signal processors.
The AD7874 is fabricated in Analog Devices’ Linear Compatible 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 hermetic dual-in-line package (DIP), in a 28-terminal leadless ceramic chip carrier (LCCC) and in a 28-pin SOIC.
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