Texas Instruments ADS126 EVM-PDK Series, User Manual, Page: 14 / 38

ADS126xEVM Hardware
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2.6.1 ADS126x Integrated Input Functions
The ADS1262 and ADS1263 provide several integrated functions on the analog inputs to support many
applications.
Table 4 summarizes the functions available on each input pin.
Table 4. ADS126x Analog Input Pin Functions
Input Pin ADC Input IDAC Output VBIAS Output External REF Input Test DAC Output GPIO
AIN0 yes yes - REF1 P - -
AIN1 yes yes - REF1 N - -
AIN2 yes yes - REF2 P - -
AIN3 yes yes - REF2 N - yes
AIN4 yes yes - REF3 P - yes
AIN5 yes yes - REF3 N - yes
AIN6 yes yes - - yes yes
AIN7 yes yes - - yes yes
AIN8 yes yes - - - yes
AIN9 yes yes - - - yes
AINCOM yes yes yes - - yes
2.6.1.1 ADC Inputs
The ADS126x has a flexible input multiplexer with 11 analog inputs. Any of the inputs can connect to the
positive input and any input can connect to the negative input. (Additionally, the ADS1263 has a second
ADC with an independent flexible input multiplexer to all input pins). Configure the inputs to provide either
single-ended or differential input measurements. The input multiplexer can also connect to several internal
signals. The internal signals are the temperature sensor, test DAC, analog power supply ([AVDD – AVSS]
/ 4), and digital power supply ([DVDD – DGND] / 4). Use the internal signals for ADC and system
functional verification or as part of an ADC diagnostic routine.
2.6.1.2 IDAC Output
The ADS126x provides dual matched current sources (IDAC1 and IDAC2) for biasing of resistive
temperature devices (RTDs), thermistors and other resistive based sensors. The IDACs can be
independently programmed and can be connected to any analog input. Each IDAC is programmable over
the range of 50 µA to 3000 µA. The internal reference must be enabled for IDAC operation.
2.6.1.3 VBIAS Output
The analog power supply is either a single or bipolar supply. For single-supply operation, the level shift
function (VBIAS) can offset the common input voltage on AINCOM to a midsupply voltage ([AVDD +
AVSS] / 2).
2.6.1.4 External REF Input
The ADC126x accepts external references (in addition to the internal and supply reference options). The
external reference inputs are shared with pins AIN0 through AIN5. ADC2 (on the ADS1263) selects a
different reference source other than the primary ADC.
2.6.1.5 Test DAC Output
Inputs AIN6 and AIN7 are programmable to output the internal test DAC voltage. The test signal output is
unbuffered; do not externally load.
2.6.1.6 GPIO
Eight inputs (AIN3 through AINCOM) are configurable as general-purpose input/outputs (GPIO). The
GPIO voltages are referenced to the analog power supply (AVDD and AVSS); therefore, the GPIOs must
use 5-V logic. The GPIOs are useful for control of external devices, as well as reading external logic
signals.
14 ADS126xEVM-PDK SBAU206 – April 2015
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