16-Bit, 250 kSPS PulSAR
ADC in MSOP
AD7685
Data Sheet
FEATURES
TYPICAL APPLICATION CIRCUIT
APPLICATIONS
Battery-powered equipment
Medical instruments
Mobile communications
Personal digital assistants (PDAs)
Data acquisition
Instrumentation
Process controls
IN+
IN–
POSITIVE INL = +0.33LSB
NEGATIVE INL = –0.50LSB
0.5
AD7685
SCK
3- OR 4-WIRE INTERFACE
(SPI, DAISY CHAIN, CS)
SDO
GND
CNV
Figure 2.
Table 1. MSOP, LFCSP/SOT-23 14-/16-/18-Bit PulSAR ADC
Type
18-Bit True
Differential
16-Bit True
Differential
16-Bit Pseudo
Differential
14-Bit Pseudo
Differential
100
kSPS
250
kSPS
AD7691
AD7684
AD7687
AD7680
AD7683
AD7940
AD7685
AD7694
AD7942
400 kSPS
to
500 kSPS
AD7690
AD7982
AD7688
AD7693
AD7686
1000
kSPS
AD7982
AD7980
AD7946
ADC
Driver
ADA4941
ADA4841
ADA4941
ADA4841
ADA4841
ADA4841
Power dissipation scales linearly with throughput.
0
–0.5
–1.0
–2.0
0
16384
32768
CODE
49152
65536
02968-005
–1.5
Figure 1. Integral Nonlinearity vs. Code
The SPI-compatible serial interface also features the ability,
using the SDI input, to daisy chain several ADCs on a single
3-wire bus or provides an optional BUSY indicator. It is
compatible with 1.8 V, 2.5 V, 3 V, or 5 V logic using the
separate supply VIO.
The AD7685 is housed in a 10-lead MSOP or a 10-lead LFCSP
with operation specified from −40°C to +85°C.
1
Rev. D
1.8V TO VDD
REF VDD VIO
SDI
The AD7685 1 is a 16-bit, charge redistribution successive
approximation, analog-to-digital converter (ADC) that operates
from a single power supply, VDD, between 2.3 V to 5.5 V. It
contains a low power, high speed, 16-bit sampling ADC with no
missing codes, an internal conversion clock, and a versatile serial
interface port. The part also contains a low noise, wide bandwidth,
short aperture delay, track-and-hold circuit. On the CNV rising
edge, it samples an analog input IN+ between 0 V to REF with
respect to a ground sense IN−. The reference voltage, REF, is
applied externally and can be set up to the supply voltage.
1.0
INL (LSB)
0 TO VREF
2.5V TO 5V
GENERAL DESCRIPTION
2.0
1.5
0.5V TO VDD
02968-001
16-bit resolution with no missing codes
Throughput: 250 kSPS
INL: ±0.6 LSB typical, ±2 LSB maximum (±0.003% of FSR)
SINAD: 93.5 dB at 20 kHz
THD: −110 dB at 20 kHz
Pseudo differential analog input range
0 V to VREF with VREF up to VDD
No pipeline delay
Single-supply operation 2.3 V to 5.5 V with
1.8 V to 5 V logic interface
Proprietary serial interface: SPI-/QSPI™-/MICROWIRE™-/DSPcompatible
Daisy-chain multiple ADCs, BUSY indicator
Power dissipation
1.4 µW at 2.5 V/100 SPS
1.35 mW at 2.5 V/100 kSPS, 4 mW at 5 V/100 kSPS
Standby current: 1 nA
10-lead package: MSOP (MSOP-8 size) and
3 mm × 3 mm LFCSP (SOT-23 size)
Pin-for-pin-compatible with 10-lead MSOP/PulSAR® ADCs
Protected by U.S. Patent 6,703,961.
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