Detailed Description; Overview; Functional Block Diagram - Texas Instruments ADS866 Series Manual

ADS8664, ADS8668
SBAS492 – JULY 2015

8 Detailed Description

8.1 Overview

The ADS8664 and ADS8668 are 12-bit data acquisition systems with 4- and 8-channel analog inputs,
respectively. Each analog input channel consists of an overvoltage protection circuit, a programmable gain
amplifier (PGA), and a second-order, antialiasing filter that conditions the input signal before being fed into a 4-
or 8-channel analog multiplexer (MUX). The output of the MUX is digitized using a 12-bit analog-to-digital
converter (ADC), based on the successive approximation register (SAR) architecture. This overall system can
achieve a maximum throughput of 500 kSPS, combined across all channels. The devices feature a 4.096-V
internal reference with a fast-settling buffer and a simple SPI-compatible serial interface with daisy-chain (DAISY)
and ALARM features.
The devices operate from a single 5-V analog supply and can accommodate true bipolar input signals up to
±2.5 × V . The devices offer a constant 1-MΩ resistive input impedance irrespective of the sampling frequency
REF
or the selected input range. The integration of multichannel precision analog front-end circuits with high input
impedance and a precision ADC operating from a single 5-V supply offers a simplified end solution without
requiring external high-voltage bipolar supplies and complicated driver circuits.

8.2 Functional Block Diagram

AIN_0P
AIN_0GND
AIN_1P
AIN_1GND
AIN_2P
AIN_2GND
AIN_3P
AIN_3GND
AIN_4P
AIN_4GND
AIN_5P
AIN_5GND
AIN_6P
AIN_6GND
AIN_7P
AIN_7GND
AUX_IN
AUX_GND
22 Submit Documentation Feedback
AVDD
1 M:
OVP
2nd-Order
PGA
LPF
OVP
1 M:
V
B0
1 M:
OVP
2nd-Order
PGA
LPF
OVP
1 M:
V
B1
1 M:
OVP
2nd-Order
PGA
LPF
OVP
1 M:
V
B2
1 M:
OVP
2nd-Order
PGA
LPF
OVP
1 M:
V
B3
1 M:
OVP
2nd-Order
PGA
LPF
OVP
1 M:
V
B4
1 M:
OVP
2nd-Order
PGA
LPF
OVP
1 M:
V
B5
1 M:
OVP
2nd-Order
PGA
LPF
OVP
1 M:
V
B6
1 M:
OVP
2nd-Order
PGA
LPF
OVP
1 M:
V
B7
AGND
Product Folder Links:
DVDD
ADC
Driver
ADC
Driver
ADC
Driver
ADC
Driver
ADC 12-Bit
SAR ADC
Driver
ADC
Oscillator
Driver
ADC
Driver
ADC
Driver
4.096-V
Reference
DGND
REFGND
Copyright © 2015, Texas Instruments Incorporated
ADS8664 ADS8668
www.ti.com
ADS8668
ADS8664
Digital
Logic
and
CS
Interface
SCLK
SDI
SDO
DAISY
REFSEL
RST/PD
ALARM
REFCAP
REFIO