ANALOG DEVICES AD7986 Service Manual
18-Bit, 2 MSPS PulSAR
V
FEATURES
18-bit resolution with no missing codes
Throughput: 2 MSPS (TURBO = high), 1.5 MSPS (TURBO = low)
Low power dissipation
15 mW at 2 MSPS, with external reference
26 mW at 2 MSPS with internal reference
INL: ±1 LSB typical, ±2.5 LSB maximum
SNR
95.5 dB, with on-chip reference
97.0 dB, with external reference
4.096 V internal reference: typical drift of 10 ppm/°C
True differential analog input voltage range: ±V
0 V to V
with V
REF
up to 5.0 V
REF
Allows use of any input range
No pipeline delay
Logic interface: 1.8 V/2.5 V/2.7 V
Serial interface: SPI/QSPI™/MICROWIRE™/DSP compatible
Ability to daisy-chain multiple ADCs with busy indicator
20-lead 4 mm × 4 mm LFCSP (QFN)
APPLICATIONS
Battery-powered equipment
Data acquisition systems
Medical instruments
Seismic data acquisition systems
REF
15 mW ADC in LFCSP (QFN)
AD7986
APPLICATION DIAGRAM
1.8
AVDD,
DVDD
GND
1
TO
2.7V
VIO
TURBO
SDI
SCK
SDO
CNV
VIO
3- OR 4-WI RE
INTERFACE:
SPI, CS
DAISY CHAIN
(TURBO = LOW)
V+
0V
TO
V
REF
V
REF
TO
0V
NOTES
1. GND REF ERS TO REFG ND, AGND, AND DGND.
15Ω
2.7nF
V–
V+
15Ω
2.7nF
V–
5V 2.5V
BVDD
IN+
AD7986
IN–
REF
10µF
Figure 1.
GENERAL DESCRIPTION
The AD7986 is an 18-bit, 2 MSPS successive approximation,
analog-to-digital converter (ADC). It contains a low power,
high speed, 18-bit sampling ADC, an internal conversion clock,
an internal reference (and buffer), error correction circuits, and
a versatile serial interface port. On the rising edge of CNV, the
AD7986 samples the voltage difference between the IN+ and
IN− pins. The voltages on these pins usually swing in opposite
phases between 0 V and V
rate turbo mode (TURBO = high) and a reduced power normal
mode (TURBO = low) for low power applications where the
power is scaled with the throughput.
In normal mode (TURBO = low), the SPI-compatible serial
interface also features the ability, using the SDI input, to daisychain several ADCs on a single 3-wire bus and provide an
optional busy indicator. It is compatible with 1.8 V, 2.5 V, and 2.7 V
using the separate VIO supply.
The AD7986 is available in a 20-lead LFCSP (QFN) with
operation specified from −40°C to +85°C.
. It features a very high sampling
REF
07956-001
Table 1. MSOP, LFCSP (QFN) 14-/16-/18-Bit PulSAR® ADCs
Type 100 kSPS 250 kSPS 400 kSPS to 500 kSPS ≥1000 kSPS ADC Dr iver
14-Bit AD7940 AD79421
16-Bit AD7680
AD7683
AD7685
AD7687
1
1
AD76881 AD79831
AD7684 AD7694
18-Bit
AD7691
1
AD76901 AD79821
AD7986 AD8021
1
Pin-for-pin compatible.
Rev. B
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.
AD7946
AD7686
AD7693
1
1
AD79801
ADA4941-1
ADA4841-x
1
ADA4941-1
1
AD7984
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Tel: 781.329.4700 www.analog.com
Fax: 781.461.3113 ©2009–2011 Analog Devices, Inc. All rights reserved.
ADA4841-x
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