SPVA065 June   2026 TIC12400-Q1

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2On-Chip ADC Front-End Architecture Overview
  6. 3Understanding the ILKG Specification in the Datasheet
    1. 3.1 Interpretation of the ±110 µA Specification
    2. 3.2 The Leakage Current Is MUX-Activated and Time-Limited
  7. 4Design Considerations with Weak Voltage Sources
    1. 4.1 Definition of a Weak Voltage Source
    2. 4.2 Mechanism of the Sampling Spike
  8. 5Quantitative Model and Error Estimation
    1. 5.1 Voltage Step During the Sampling Window
    2. 5.2 Steady-State Offset with High-Impedance Sources
  9. 6Design Mitigation Methods
    1. 6.1 Method 1: Strengthen the Voltage Source
    2. 6.2 Method 2: External RC Compensation (Recommended)
    3. 6.3 Method 3: Static Offset Calibration
  10. 7Summary
  11. 8References

7 Summary

The input leakage current (ILKG) of up to ±110µA specified in the TIC12400-Q1 datasheet for 0mA wetting current mode is a worst-case bound that covers all operating conditions, supply voltages, temperatures, and internal device states. It is not a continuous DC current present at the INx pin. Bench evaluation confirms that this leakage current is injected only during the brief MUX-active sampling window associated with each ADC or comparator measurement, and that its duration is directly determined by the configured sampling time (Tadc or Tcomp).

When the external voltage applied to the INx pin is derived from a high-impedance source, such as a passive resistor divider or a slide rheostat—this transient leakage current charges the capacitance on the INx node and produces narrow voltage spikes synchronized with each polling event. If the RC discharge time constant is long relative to the polling period, a quasi-static offset can accumulate on the INx node, causing the ADC to report a value higher than the true steady-state input voltage. Because this behavior is entirely deterministic and repeatable, it can be effectively managed through one or more of the following system-level approaches: strengthening the external voltage source with a low-impedance buffer; adding appropriate external capacitance to reduce the transient voltage step per Equation 1; or characterizing the residual offset as a static, calibratable error. With these design considerations properly addressed, the TIC12400-Q1 can reliably perform analog voltage sensing using passive signal sources across a wide range of automotive BCM and ZCM applications.