16-Bit, 8-Channel,
250 kSPS PulSAR® ADC
Preliminary Technical Data
AD7689
FEATURES
FUNCTIONAL BLOCK DIAGRAM
2.7V to 5V
0.5V to 4.096V
0.5V to VDD
16-bit resolution with no missing codes
8-channel multiplexer with:
Unipolar single ended or
22μF
0.1μF
REFIN
REF
VDD
Differential (GND sense)/Bipolar inputs
Throughput: 250 kSPS
INL/DNL: 0.6 LSB typical
1.8V to
VDD
Band Gap
REF
VIO
AD7689
Temp
Sensor
Dynamic range: 93.5 dB
CNV
IN0
IN1
IN2
IN3
IN4
IN5
IN6
IN7
SINAD: 92.5 dB @ 20 kHz
THD: −100 dB @ 20 kHz
Analog input range:
0 V to VREF with VREF up to VDD
Reference:
SCK
SDO
DIN
16-Bit SAR
ADC
SPI Serial
Interface
MUX
1-Pole
LPF
Sequencer
Internal selectable 2.5 V/4.096 V or
External buffered (up to 4.096 V)
External (up to VDD)
COM
GND
Figure 1.
Internal temperature sensor
Channel sequencer, selectable 1-pole filter, BUSY indicator
No pipeline delay, SAR architecture
Single-supply 2.7V – 5.5 V operation with
1.8 V to 5 V logic interface
Serial interface SPI®/QSPI™/MICROWIRE™/DSP compatible
Power dissipation:
6 mW @ 5 V/100 kSPS
Table 1. Multichannel14-/16-Bit PulSAR ADC
500
kSPS
250
ADC
Driver
Type
Channels kSPS
14-Bit
16-Bit
16-Bit
8
4
8
AD7949
AD7682
AD7689
ADA4841-x
ADA4841-x
ADA4841-x
AD7699
Standby current: 1 nA
20-lead 4 mm × 4 mm LFCSP package
GENERAL DESCRIPTION
The AD7689 is an 8-channel 16-bit, charge redistribution
successive approximation register (SAR), analog-to-digital
converter (ADC) that operates from a single power supply, VDD.
APPLICATIONS
Battery-powered equipment
Medical instruments
Mobile communications
Personal digital assitants
Data acquisition
Seismic data acquisition systems
Instrumentation
Process Control
The AD7689 contains all of the components for use in a multi-
channel, low power, data acquisition system including: a true 16-
bit SAR ADC with no missing codes; an 8-channel, low crosstalk
multiplexer useful for configuring the inputs as single ended (with
or without ground sense), differential or bipolar; an internal low
drift reference (selectable 2.5V or 4.096V) and buffer; a
temperature sensor; a selectable 1-pole filter; and a sequencer
useful when channels are continuously scanned in order.
The AD7689 uses a simple SPI interface for writing to the
configuration register and receiving conversion results. The SPI
interface uses a separate supply, VIO, which is set to the host logic
level.
Power dissipation scales with throughput.
The AD7689 is housed in a tiny 20-lead LFCSP with operation
specified from −40°C to +85°C.
Rev. PrC
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