LMP91000: Component Recommendations for High-Speed, Low-Power, Miniaturized Potentiostat

Tool/software:

Hello TI Support Team,

We are designing a custom, battery-powered potentiostat for a high-speed electrochemical sensing application and would appreciate your component recommendations.

Our primary challenge is balancing speed, resolution, power, and size. The goal is to produce filtered sensor current data at a rate of at least 50 kSPS (a 20 µs interval), with a resolution of 10 nA.

1. Integrated Solutions: Our research has led us to integrated potentiostat AFEs like the LMP91000 or AD5940. However, to achieve high fidelity, low noise data every 20us, after ADC oversampling and decimation filters is not fast enough in most integrated solutions. 

• Are there any TI integrated potentiostat AFEs that can meet our speed and resolution requirements?
• Alternatively, could an integrated SOC (with integrated low power ADC, DAC, BLE) work with OTS (LMP91000 etc) or even custom discrete AFE to meet our our performance targets?

2. Discrete Component Requirements: If a fully integrated solution isn't feasible, we are considering a discrete solution. We would appreciate your recommendations for a suitable op-amp (for the TIA), for control amplifier (high current driving capability and slew rate), unity gain buffer and an ADC. Our key requirements are summarized below.

• Overall Performance
  • Measurement Goal: Capture input current transients up to a maximum of 20 µA.
    1. Resolution: At least 10 nA.
    2. Data Rate: Provide a final, oversampled and filtered data point every 20 µs or faster (≥ 50 kSPS - not raw unfiltered sampling).
• Component Specifications
  1. Transimpedance Amplifier (TIA):
     1. Must be fast enough to accurately capture the current transient within the 20 µs window.
     2. Needs ultra-low noise, low input bias current, and low offset/drift to resolve 10 nA. A FET-input is highly preferred.
  2. Control Amplifier
     1. Must have high current driving capability and sufficient slew rate to drive electrochemical cell from DAC output.
  3. Unity Gain Buffer
     1. Needs ultra-low noise, low input bias current, and low offset/drift to resolve 10 nA. A FET-input is highly preferred.
  4. Analog-to-Digital Converter (ADC):
     1. Resolution: 16-24 bits (to minimize quantization noise).
     2. Sampling Rate: Must be high enough to allow for oversampling and digital filtering to achieve the final ≥ 50 kSPS data rate (1 MSPS+).
• System Constraints
  1. A single positive supply is strongly preferred to reduce solution size.
  2. The device is battery-powered, so low quiescent current (Iq) is critical for all component selections. We would be open to using SW controlled FETs to turn off AFE for power savings in case low power parts don't meet performance or size specs. 
  3.  A compact footprint is a key design driver.
• Development Support
  1. Finally, development support is a critical factor in our component selection.
  2. Parts with available evaluation kits, reference designs, or firmware examples would be highly preferred to help accelerate our design cycle.

Thank you for your time and assistance.