16-Bit, 1.5 LSB INL, 500 kSPS PulSAR™
Differential ADC in MSOP/LFCSP
AD7688
Data Sheet
FEATURES
APPLICATION DIAGRAM
APPLICATIONS
Battery-powered equipment
Data acquisitions
Instrumentation
Medical instruments
Process controls
1.5
POSITIVE INL = +0.31LSB
NEGATIVE INL = –0.39LSB
0.5V TO 5V
VREF
0
IN+
IN–
VREF
5V
1.8V TO VDD
REF VDD VIO
SDI
AD7688
SCK
3- OR 4-WIRE INTERFACE
(SPI, DAISY CHAIN, CS)
SDO
GND
CNV
0
02973-002
16-bit resolution with no missing codes
Throughput: 500 kSPS
INL: ±0.4 LSB typ, ±1.5 LSB max (±23 ppm of FSR)
Dynamic range: 96.5 dB
SNR: 95.5 dB at 20 kHz
THD: −118 dB at 20 kHz
True differential analog input range
±VREF
0 V to VREF with VREF up to VDD on both inputs
No pipeline delay
Single-supply 5 V operation with
1.8 V/2.5 V/3 V/5 V logic interface
Proprietary serial interface
SPI®/QSPI™/MICROWIRE™/DSP-compatible 1
Daisy-chain multiple ADCs and BUSY indicator
Power dissipation
3.75 mW at 5 V/100 kSPS
3.75 µW at 5 V/100 SPS
Standby current: 1 nA
10-lead MSOP (MSOP-8 size) and
3 mm × 3 mm LFCSP (SOT-23 size)
Pin-for-pin compatible with AD7685, AD7686, and AD7687
Figure 2.
Table 1. MSOP, LFCSP/SOT-23 16-Bit PulSAR ADC
Type
True Differential
Pseudo
Differential/Unipolar
Unipolar
100 kSPS
AD7684
AD7683
250 kSPS
AD7687
AD7685
AD7694
500 kSPS
AD7688
AD7686
AD7680
GENERAL DESCRIPTION
The AD7688 is a 16-bit, charge redistribution, successive
approximation, analog-to-digital converter (ADC) that operates
from a single 5 V power supply, VDD. 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 the voltage difference between IN+ and IN− pins.
The voltages on these pins usually swing in opposite phase
between 0 V and REF. The reference voltage, REF, is applied
externally and can be set up to the supply voltage.
Its power scales linearly with throughput.
1.0
–0.5
The SPI-compatible serial interface also features the ability,
using the SDI input, to daisy-chain several ADCs on a single,
3-wire bus and 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.
–1.0
The AD7688 is housed in a 10-lead MSOP or a 10-lead LFCSP
with operation specified from −40°C to +85°C.
0
02973-001
INL (LSB)
0.5
–1.5
0
16384
32768
CODE
49152
65535
1
Protected by U.S. Patent 6,703,961.
Figure 1. Integral Nonlinearity vs. Code
Rev. B
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