LC
2
MOS 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
INPUT
SCALING
AD7870/AD7875/
AD7876
TRACK-AND-HOLD
COMP
3V
REFERENCE
12-BIT
DAC
CLK
CLOCK
SAR +
COUNTER
12/8/CLK
CONTROL LOGIC
CONVST
PARALLEL
AND SERIAL
INTERFACE
07730-001
CS
RD BUSY/INT
DB11
DB0
DGND
V
SS
Figure 1.
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.
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.
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.
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.
2.
3.
Rev. C
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 that may result from its use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarks and registered trademarks are the property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
www.analog.com
Fax: 781.461.3113 ©1997–2009 Analog Devices, Inc. All rights reserved.
AD [ ANALOG DEVICES ]
