16-Bit, 250 kSPS PulSAR
ADC in MSOP/QFN
AD7685
APPLICATION DIAGRAM
FEATURES
0.5V TO VDD
2.5V TO 5V
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 @ 20 kHz
THD: −110 dB @ 20 kHz
Pseudo differential analog input range
0 V to VREF with VREF up to VDD
VIO
1.8V TO VDD
REF VDD
0 TO VREF
SDI
SCK
SDO
CNV
IN+
AD7685
3- OR 4-WIRE INTERFACE
(SPI, DAISY CHAIN, CS)
IN–
GND
No pipeline delay
Single-supply operation 2.3 V to 5.5 V with
1.8 V to 5 V logic interface
Serial interface SPI®-/QSPI™-/MICROWIRE™-/DSP-compatible
Daisy-chain multiple ADCs, BUSY indicator
Power dissipation
1.4 μW @ 2.5 V/100 SPS
1.35 mW @ 2.5 V/100 kSPS, 4 mW @ 5 V/100 kSPS
Standby current: 1 nA
Figure 2.
Table 1. MSOP, QFN (LFCSP)/SOT-23
14-/16-/18-Bit PulSAR ADC
400 kSPS
to
500 kSPS kSPS
100
kSPS
250
1000
ADC
Driver
Type
kSPS
18-Bit True
Differential
16-Bit True
Differential
AD7691 AD7690
AD7982
AD7982 ADA4941
ADA4841
10-lead package: MSOP (MSOP-8 size) and
3 mm × 3 mm QFN (LFCSP) (SOT-23 size)
Pin-for-pin-compatible with 10-lead MSOP/QFN PulSAR® ADCs
AD7684 AD7687 AD7688
AD7693
ADA4941
ADA4841
16-Bit Pseudo AD7680 AD7685 AD7686
Differential AD7683 AD7694
AD7980 ADA4841
APPLICATIONS
14-Bit Pseudo AD7940 AD7942 AD7946
Differential
ADA4841
Battery-powered equipment
Medical instruments
Mobile communications
Personal digital assistants (PDAs)
Data acquisition
GENERAL DESCRIPTION
The AD7685 is a 16-bit, charge redistribution successive
Instrumentation
Process controls
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.
2.0
POSITIVE INL = +0.33LSB
NEGATIVE INL = –0.50LSB
1.5
1.0
0.5
0
Power dissipation scales linearly with throughput.
–0.5
–1.0
–1.5
–2.0
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.
0
16384
32768
CODE
49152
65536
The AD7685 is housed in a 10-lead MSOP or a 10-lead QFN
(LFCSP) with operation specified from −40°C to +85°C.
Figure 1. Integral Nonlinearity vs. Code.
Rev. B
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