Datasheet ADS1015

Device
Microcontroller
Signal
Conditioning
(RC Filters
and
Amplifiers)
Supply
Generation
Connector
or Antenna
Ground Fill or
Ground Plane
Optional: Split
Ground Cut
Ground Fill or
Ground Plane
Optional: Split
Ground Cut
Interface
Transceiver
Ground Fill or
Ground Plane
Ground Fill or
Ground Plane
37
ADS1013 , ADS1014 , ADS1015
www.ti.com SBAS473E –MAY 2009–REVISED JANUARY 2018
Product Folder Links: ADS1013 ADS1014 ADS1015
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11 Layout
11.1 Layout Guidelines
Employ best design practices when laying out a printed-circuit board (PCB) for both analog and digital
components. For optimal performance, separate the analog components [such as ADCs, amplifiers, references,
digital-to-analog converters (DACs), and analog MUXs] from digital components [such as microcontrollers,
complex programmable logic devices (CPLDs), field-programmable gate arrays (FPGAs), radio frequency (RF)
transceivers, universal serial bus (USB) transceivers, and switching regulators]. An example of good component
placement is shown in Figure 33. Although Figure 33 provides a good example of component placement, the
best placement for each application is unique to the geometries, components, and PCB fabrication capabilities
employed. That is, there is no single layout that is perfect for every design and careful consideration must always
be used when designing with any analog component.
Figure 33. System Component Placement
The following outlines some basic recommendations for the layout of the ADS101x to get the best possible
performance of the ADC. A good design can be ruined with a bad circuit layout.
• Separate analog and digital signals. To start, partition the board into analog and digital sections where the
layout permits. Route digital lines away from analog lines. This prevents digital noise from coupling back into
analog signals.
• Fill void areas on signal layers with ground fill.
• Provide good ground return paths. Signal return currents flow on the path of least impedance. If the ground
plane is cut or has other traces that block the current from flowing right next to the signal trace, it has to find
another path to return to the source and complete the circuit. If it is forced into a larger path, it increases the
chance that the signal radiates. Sensitive signals are more susceptible to EMI interference.
• Use bypass capacitors on supplies to reduce high-frequency noise. Do not place vias between bypass
capacitors and the active device. Placing the bypass capacitors on the same layer as close to the active
device yields the best results.
• Consider the resistance and inductance of the routing. Often, traces for the inputs have resistances that react
with the input bias current and cause an added error voltage. Reduce the loop area enclosed by the source
signal and the return current in order to reduce the inductance in the path. Reduce the inductance to reduce
the EMI pickup, and reduce the high frequency impedance seen by the device.
• Differential inputs must be matched for both the inputs going to the measurement source.
• Analog inputs with differential connections must have a capacitor placed differentially across the inputs. Best
input combinations for differential measurements use adjacent analog input lines such as AIN0, AIN1 and
AIN2, AIN3. The differential capacitors must be of high quality. The best ceramic chip capacitors are C0G
(NPO), which have stable properties and low-noise characteristics.