Texas Instruments ADS125H02 Quick Start Manual page 2

Design Notes
1. Use supply decoupling capacitors for both the analog and digital supplies. For the high-voltage analog
supply (HV_AVDD and HV_AVSS), place a 1.0-µF capacitor between the pins and place 0.1-µF
capacitors from each supply to the ground plane. Connect 0.1-µF and 10-µF capacitors in parallel at
AVDD to the ground plane. Connect a 1.0-µF capacitor from DVDD to the ground plane. Connect a
1.0-µF capacitor from BYPASS to the ground plane. For details on power supply recommendations,
see the ADS125H02 ±20-V Input, 2-Channel, 40- kSPS, 24-Bit, Delta-Sigma ADC With PGA and
Voltage Reference Data
2. To minimize input current leakage, connect unused analog inputs to AGND when operating the device
with bipolar supplies, or connect unused inputs to AVDD when operating the device with a unipolar
supply.
3. Program unused GPIOs as outputs (default setting). If any GPIOs are programmed as inputs, the
GPIO must not be allowed to float (unconnected), otherwise AVDD power-supply leakage current may
result.
4. Consider adding TVS diodes between the high-voltage supplies (HV_AVDD to HV_AVSS) to provide
overvoltage protection and avoid violating the absolute maximum rating of 38V. A TVS diode such as
the TVS3300 provides a 33.0-V stand-off voltage (V
minimizing the current leakage of the diode, but has a typical break-down voltage (V
voltage (V ) of 35.8 V and 38.0 V, respectively (assuming a peak pulse current I
C
effectively protecting the ADC from an EOS event. For more details on EOS in ADCs, see
Labs: EOS and ESD in
5. When possible, use C0G (NPO) ceramic capacitors for input filtering. The dielectric used in these
capacitors provides the most stable electrical properties over voltage, frequency, and temperature
changes.
6. Input filtering for the ADC inputs and the reference inputs are selected using standard capacitor values
and 1% resistor values. For an example design and analysis of these filters, see the
Measurements and Filtering Using the ADS1148 and ADS1248 Family of Devices Application
Component Selection
1. Identify the system components:
a. Given the following specifications are:
• Input voltage range ≤ ±12.0V
• Two voltage input channels, and two current input channels
Data rate ≤ 10 kSPS
•
• 0.05%FS accuracy, or better
• Optimized for cost
b. Products selected:
• ADS125H02
and voltage reference. This device meets the input voltage range, accuracy, and data rate
requirements, and it integrates a precision voltage reference, and GPIOs helping in cost
optimization.
• MUX509
expanding to 4-channels using a single ADC for cost optimization.
• Burden resistor:
A burden resistor converts the current to a limited voltage to do measurements in the current
measurement mode, a 250-Ω resistor was selected given the desired current range
measurements (0 to 20mA), and a target burden voltage of 5.0V. Using a precision resistor
ensures that the resistor does not become the limiting factor for system accuracy, the following
specifications can be used as :
– Accuracy ≤ 0.1%
– Temperature coefficient ≤ 20 ppm/°C
– Power rating ≥ 0.5W
• Alternative and similar devices are listed in
2
Four-channel, differential input, DAQ front-end circuit with configurable
voltage and current inputs
Sheet.
ADC.
is a 24-bit, ±20-V input, delta-sigma ADC with integrated high-input voltage PGA
is a differential 4:1, 36-V, precision, analog multiplexer. This device enables
Copyright © 2019, Texas Instruments Incorporated
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SBAA386 – December 2019
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