Texas Instruments ADS8684A Manual

ADS868xA 16-Bit, 500-kSPS, 4- and 8-Channel, Single-Supply, SAR ADCs with
1 Features
• 16-Bit ADCs with Integrated Analog Front-End
1
• 4-, 8-Channel MUX with Auto and Manual Scan
• Channel-Independent Programmable Inputs:
– ±10.24 V, ±5.12 V, ±2.56 V, ±1.28 V, ±0.64 V
– 10.24 V, 5.12 V, 2.56 V, 1.28 V
• 5-V Analog Supply: 1.65-V to 5-V I/O Supply
• Constant Resistive Input Impedance: 1 MΩ
• Input Overvoltage Protection: Up to ±20 V
• On-Chip, 4.096-V Reference with Low Drift
• Excellent Performance:
– 500-kSPS Aggregate Throughput
– DNL: ±0.5 LSB; INL: ±0.75 LSB
– Low Drift for Gain Error and Offset
– SNR: 92 dB; THD: –102 dB
– Low Power: 65 mW
• AUX Input → Direct Connection to ADC Inputs
• ALARM → High and Low Thresholds per Channel
• SPI™-Compatible Interface with Daisy-Chain
• Industrial Temperature Range: –40°C to 125°C
• TSSOP-38 Package (9.7 mm × 4.4 mm)
Block Diagram
AVDD
1 M:
AIN_0P
OVP
2nd-Order
PGA
AIN_0GND LPF
OVP
1 M:
V
B0
1 M:
AIN_1P OVP
2nd-Order
PGA
AIN_1GND
LPF
OVP
1 M:
V
B1
1 M:
AIN_2P OVP
2nd-Order
PGA
AIN_2GND
LPF
OVP
1 M:
V
B2
1 M:
AIN_3P
OVP
2nd-Order
PGA
AIN_3GND LPF
OVP
1 M:
V
B3
1 M:
AIN_4P
OVP
2nd-Order
PGA
AIN_4GND LPF
OVP
1 M:
V
B4
1 M:
AIN_5P OVP
2nd-Order
PGA
AIN_5GND
LPF
OVP
1 M:
V
B5
1 M:
AIN_6P OVP
2nd-Order
PGA
AIN_6GND
LPF
OVP
1 M:
V
B6
1 M:
AIN_7P
OVP
2nd-Order
PGA
AIN_7GND LPF
OVP
1 M:
V
B7
AUX_IN
AUX_GND
AGND
1
An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,
intellectual property matters and other important disclaimers. PRODUCTION DATA.
Sample &
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Bipolar Input Ranges
DVDD
ADS8688A
ADC
ADS8684A
Driver
ADC
Driver
Digital
ADC
Logic
Driver
and
CS
Interface
SCLK
ADC
Driver
SDI
SDO
16-Bit
ADC
Driver SAR ADC
DAISY
REFSEL
ADC
Oscillator
Driver
RST / PD
ALARM
ADC
REFCAP
Driver
REFIO
ADC
Driver
4.096-V
Reference
DGND
REFGND
Tools &
Technical
Software
Documents
2 Applications
• Power Automation
• Protection Relays
• PLC Analog Input Modules
3 Description
The ADS8684A and ADS8688A are 4- and 8-
channel, integrated data acquisition systems based
on a 16-bit successive approximation (SAR) analog-
to-digital converter (ADC), operating at a throughput
of 500 kSPS. The devices feature integrated analog
front-end circuitry for each input channel with
overvoltage protection up to ±20 V, a 4- or 8-channel
multiplexer with automatic and manual scanning
modes, and an on-chip, 4.096-V reference with low
temperature drift. Operating on a single 5-V analog
supply, each input channel on the devices can
support true bipolar input ranges of ±10.24 V,
±5.12 V, ±2.56 V, ±1.28V and ±0.64V, as well as
unipolar input ranges of 0 V to 10.24 V, 0 V to 5.12 V,
0 V to 2.56 V and 0 V to 1.28 V. The gain of the
analog front-end for all input ranges is accurately
trimmed to ensure a high dc precision. The input
range selection
independent for each channel. The devices offer a
1-MΩ constant resistive input impedance irrespective
of the selected input range.
The ADS8684A and ADS8688A offer a simple SPI-
compatible serial interface to the digital host and also
support daisy-chaining of multiple devices. The digital
supply operates from 1.65 V to 5.25 V, enabling
direct interface to a wide range of host controllers.
Device Information
PART NUMBER
ADS868xA
(1) For all available packages, see the orderable addendum at
the end of the datasheet.
Gain Error versus Temperature
0.05
0.03
0.01
-0.01
-0.03
-0.05
±40
Support & Reference
Community
Design
ADS8684A, ADS8688A
SBAS680 – JULY 2015
is software-programmable
(1)
PACKAGE BODY SIZE (NOM)
TSSOP (38) 9.70 mm × 4.40 mm
---- ± 2.5*V ---- “ 1.25*V
REF, REF
---- “ 0.625*V ------“0.3125*V
REF, REF
-------“0.156 V ---- + 2.5*V
REF, REF
---- + 1.25*V ---- + 0.625*V
REF, REF
---- + 0.3125*V
REF
26 59 92
±7
o
Free-Air Temperature ( C)
and
125
C039