OPA626 Datasheet, PDF (24/39 Pages) Texas Instruments – Analog-to-Digital Converter (ADC) Drivers

OPA626, OPA2626
SBOS690 – JULY 2016
9 Application and Implementation
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NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
9.1 Application Information
The OPAx626 family consists of precision, high-speed, voltage-feedback operational amplifiers. Fast settling to
16-bit levels, low THD, and low noise make the OPAx626 family suitable for driving SAR ADC inputs and
buffering precision voltage references. With a wide power-supply voltage range from 2.7 V to 5.5 V, and
operating from –40°C to +125°C, the OPAx626 family is suitable for a variety of high-speed, industrial
applications. The following sections show application information for the OPAx626 family. For simplicity, power-
supply decoupling capacitors are not shown in these diagrams.
9.2 Typical Applications
9.2.1 Single-Supply, 16-Bit, 1-MSPS SAR ADC Driver
1 kO
1 kO
VREF / 4
5V
+ _OPA626
RFLT
4.7 O
10 nF
CFLT
VREF 3.3 V
REF _AVDD
ADS8860
GND
4.7 O
RFLT
Copyright © 2016, Texas Instruments Incorporated
Figure 61. Single-Supply, 16-Bit, 1-MSPS SAR ADC Driver
9.2.1.1 Design Requirements
An SAR ADC, such as the ADS8860 device, uses sampling capacitors on the data converter input. During the
signal acquisition phase, these sampling capacitors are connected to the ADC analog input terminals, AINP and
AINN, through a set of switches. After the acquisition period has elapsed, the internal sampling capacitors are
disconnected from the input terminals and connected to the ADC input through a second set of switches, during
this period the ADC is performing the analog-to-digital conversion. Figure 62 illustrates this architecture.
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