Some ADCs need more from your front-end than you might expect. You can select a low-noise, high-performance ADC part and still fall short of your accuracy target. One common reason is simple but easy to miss: the driver cannot properly drive the ADC.
If the amplifier is not fast enough, performance issues in terms of settling and kickback behavior, harmonic distortion and gain errors will show up.
Signal Chain Designer (SCD), helps bridge this gap by checking whether the circuitry in front of the ADC can meet the system requirements.
Checking ADC Drive Capability in Signal Chain Designer
To see how this plays out, consider a simple example using a sensor with approximately 1 kΩ output impedance and adding a 16-bit, 1 MSPS ADC to the signal chain. When this configuration is created in the tool, an ADC that meets these requirements (e.g. AD4004) is automatically selected. However, a warning appears indicating that the ADC requires a driver circuit. This is an important first indication that the ADC can’t sample the input source directly.
Example of ADC Driving Checks in Signal Chain Designer
What makes the tool useful is that it does not stop at flagging the issue, it also guides you toward a solution. Once the warning is clicked and the suggestion to insert a buffer is followed, the tool automatically chooses a suitable fast amplifier, ensuring that the ADC input is properly driven.
Full Signal Chain View: After inserting a Buffer Stage at ADC Input (as tool recommended)
Validating Your Amplifier Choice
In practice, designers may have preferred amplifier choices and want to verify if they are suitable. Signal Chain Designer makes this straightforward. Selecting an amplifier that is too slow for the ADC immediately triggers a warning, indicating insufficient gain bandwidth.
Scenario: User Checking if Preferred Amplifier Works with the ADC
Signal Chain Designer offers a product selection table where you can explore alternative parts. (For more information on this feature, you may refer to this tech note). Switching to a faster device, such as the ADA4610, removes the warning, confirming that the amplifier can meet the required performance. This provides a quick and reliable way to validate design decisions.
Full Signal Chain View: No Warning Flags when Driver with Higher Bandwidth was Selected
When Performance Requirements Increase
The importance of driver capability becomes even more evident as system requirements increase.
Let's say the target requirements changed as follows:
- 16-bit → 24-bit
- 1 MSPS → 2 MSPS
In this case, the previous solution doesn’t work and you get a warning, indicating that the driver is no longer sufficient.
Inserting a buffer under these new conditions results in the selection of a faster amplifier. This highlights a key point: driver requirements scale with both resolution and sampling rate. A design that works at lower resolution and sample rates may fail when specifications are tightened.
A Deeper Dive with the ADC Driver Tool
If you want to understand what’s really happening behind the scenes, try out the ADC Driver Tool where you can observe effects such as distortion and input kickback settling, offering a clearer picture of why certain drivers succeed or fail.
Precision Studio’s ADC Driver Tool
Not all amplifiers are able to drive your ADC to meet the system level requirements, and these limitations aren’t always obvious. Signal Chain Designer makes this process more transparent by identifying weak drivers, suggesting appropriate solutions, and adapting recommendations as system requirements change.
For more information, this training video shows you how to use the Signal Chain Designer and ADC Driver Tool to make sure you have a strong enough driver to meet the ADC’s target specifications.