Texas Instruments ADS868 Series Manual

ADS868x 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 Input
Ranges:
– Bipolar: ±10.24 V, ±5.12 V, ±2.56 V
– Unipolar: 10.24 V, 5.12 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
• SPI™-Compatible Interface with Daisy-Chain
• Industrial Temperature Range: –40°C to 125°C
• TSSOP-38 Package (9.7 mm × 4.4 mm)
Simplified 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.
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DGND REFGND
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Documents

2 Applications

• Power Automation
• Protection Relays
• PLC Analog Input Modules

3 Description

The ADS8684 and ADS8688 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, and ±2.56 V, as well as unipolar input
ranges of 0 V to 10.24 V and 0 V to 5.12 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 is software-programmable and
independent for each channel. The devices offer a
1-MΩ constant resistive input impedance irrespective
of the selected input range.
The ADS8684 and ADS8688 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
ADS868x
(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 ±7
Support & Reference
Community
Design
ADS8684, ADS8688
SBAS582C – JULY 2014 – REVISED APRIL 2015
(1)
PACKAGE BODY SIZE (NOM)
TSSOP (38) 9.70 mm × 4.40 mm
-----
± 2.5*V
----- ± 1.25*V
----- ± 0.625*V
------ +2.5*V
REF
------+1.25*V
26 59 92
o
Free-Air Temperature ( C)
REF
REF
REF
REF
125
C026