AD7870_15 Datasheet, PDF (1/28 Pages) Analog Devices – LC MOS Complete, 12-Bit, 100 kHz, Sampling ADCs

LC²MOS Complete,
12-Bit, 100 kHz, Sampling ADCs
AD7870/AD7875/AD7876
FEATURES
Complete monolithic 12-bit ADCs with
2 μs track-and-hold amplifier
8 μs ADC
On-chip reference
Laser-trimmed clock
Parallel, byte, and serial digital interface
72 dB SNR at 10 kHz input frequency
(AD7870, AD7875)
57 ns data access time
Low power: −60 mW typical
Variety of input ranges
±3 V for AD7870
0 V to +5 V for AD7875
±10 V for AD7876
FUNCTIONAL BLOCK DIAGRAM
AGND
REF OUT
V_IN
V_DD
AD7870/AD7875/
INPUT
AD7876
SCALING
TRACK-AND-HOLD
3V
REFERENCE
12-BIT
DAC
COMP
CLK
12/8/CLK
CONVST
CLOCK
CONTROL LOGIC
PARALLEL
AND SERIAL
INTERFACE
SAR +
COUNTER
GENERAL DESCRIPTION
The AD7870/AD7875/AD7876 are fast, complete, 12-bit
analog-to-digital converters (ADCs). These converters consist
of a track-and-hold amplifier, an 8 μs successive approximation
ADC, a 3 V buried Zener reference, and versatile interface logic.
The ADCs feature a self-contained internal clock which is laser
trimmed to guarantee accurate control of conversion time. No
external clock timing components are required; the on-chip
clock may be overridden by an external clock if required.
The parts offer a choice of three data output formats: a single,
parallel, 12-bit word; two 8-bit bytes or serial data. Fast bus
access times and standard control inputs ensure easy interfacing
to modern microprocessors and digital signal processors.
All parts operate from ±5 V power supplies. The AD7870 and
AD7876 accept input signal ranges of ±3 V and ±10 V, respec-
tively, while the AD7875 accepts a unipolar 0 V to +5 V input
range. The parts can convert full power signals up to 50 kHz.
The AD7870/AD7875/AD7876 feature dc accuracy specifica-
tions, such as linearity, full-scale and offset error. In addition,
the AD7870 and AD7875 are fully specified for dynamic
performance parameters including distortion and signal-to-
noise ratio.
CS RD BUSY/INT DB11 DB0
Figure 1.
DGND V_SS
The parts are available in a 24-pin, 0.3 inch-wide, plastic or
hermetic dual-in-line package (DIP). The AD7870 and AD7875
are available in a 28-pin plastic leaded chip carrier (PLCC),
while the AD7876 is available and in a 24-pin small outline
(SOIC) package.
PRODUCT HIGHLIGHTS
1. Complete 12-bit ADC on a chip.
The AD7870/AD7875/AD7876 provide all the functions
necessary for analog-to-digital conversion and combine a
12-bit ADC with internal clock, track-and-hold amplifier
and reference on a single chip.
2. Dynamic specifications for DSP users.
The AD7870 and AD7875 are fully specified and tested for
ac parameters, including signal-to-noise ratio, harmonic
distortion and intermodulation distortion.
3. Fast microprocessor interface.
Data access times of 57 ns make the parts compatible with
modern 8-bit and 16-bit microprocessors and digital signal
processors. Key digital timing parameters are tested and
guaranteed over the full operating temperature range.
Rev. C
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