18-Bit, 2.5 LSB INL, 100 kSPS SAR ADC
AD7678
Rev. A
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 ©2003–2009 Analog Devices, Inc. All rights reserved.
FEATURES
18-bit resolution with no missing codes
No pipeline delay (SAR architecture)
Differential input range: ±V
REF
(V
REF
up to 5 V)
Throughput: 100 kSPS
INL: ±2.5 LSB max (±9.5 ppm of full scale)
Dynamic range: 103 dB typ (V
REF
= 5 V)
S/(N+D): 100 dB typ @ 2 kHz (V
REF
= 5 V)
Parallel (18-,16-, or 8-bit bus) and serial 5 V/3 V interface
SPI®/QSPI™/MICROWIRE™/DSP compatible
On-board reference buffer
Single 5 V supply operation
Power dissipation: 18 mW @ 100 kSPS
180 μW @ 1 kSPS
48-lead LQFP or 48-lead LFCSP package
Pin-to-pin compatible upgrade of AD7674/AD7676/AD7679
APPLICATIONS
CT scanners
High dynamic data acquisition
Geophone and hydrophone sensors
- replacement (low power, multichannel)
Instrumentation
Spectrum analysis
Medical instruments
GENERAL DESCRIPTION
The AD7678 is an 18-bit, 100 kSPS, charge redistribution SAR,
fully differential analog-to-digital converter that operates on a
single 5 V power supply. The part contains a high speed 18-bit
sampling ADC, an internal conversion clock, an internal
reference buffer, error correction circuits, and both serial and
parallel system interface ports.
The part is available in 48-lead LQFP or 48-lead LFCSP
packages with operation specified from –40°C to +85°C.
FUNCTIONAL BLOCK DIAGRAM
SWITCHED
CAP DAC
18
CONTROL LOGIC AND
CALIBRATION CIRCUITRY
CLOCK
AD7678
D[17:0]
BUSY
RD
CS
MODE0
OGND
OVDD
DGNDDVDD
AVDD
AGND
REF
REFGND
IN+
IN–
PD
RESET
SERIAL
PORT
PARALLEL
INTERFACE
CNVST
PDBUF
REFBUFIN
MODE1
03084–0–001
Figure 1. Functional Block Diagram
Table 1. PulSAR Selection
Type/kSPS 100–250 500–570
800–
1000
Pseudo-
Differential
AD7651
AD7660/AD7661
AD7650/AD7652
AD7664/AD7666
AD7653
AD7667
True Bipolar AD7663 AD7665 AD7671
True
Differential
AD7675 AD7676 AD7677
18-Bit AD7678 AD7679 AD7674
Multichannel/
Simultaneous
AD7654
AD7655
PRODUCT HIGHLIGHTS
1. High Resolution, Fast Throughput.
The AD7678 is a 100 kSPS, charge redistribution, 18-bit
SAR ADC (no latency).
2. Excellent Accuracy.
The AD7678 has a maximum integral nonlinearity of
2.5 LSB with no missing 18-bit codes.
3. Serial or Parallel Interface.
Versatile parallel (18-, 16-, or 8-bit bus) or 2-wire serial
interface arrangement compatible with both 3 V and
5 V logic.
