SBOA367B December   2019  – June 2022 TLV9001 , TLV9002 , TLV9004 , TLV9051 , TLV9052 , TLV9054 , TLV9061 , TLV9062 , TLV9064

 

  1.   Designing for TLV90xxS operational amplifiers with shutdown
  2.   Trademarks
  3. 1 Introduction
  4. 2 Shutdown Specifications
  5. 3  SHDN Pin Limits and Connections
  6. 4 Output Behavior During Enable and Shutdown
  7. 5 Enable Time and Shutdown Time Factors
    1. 5.1 Quiescent Current
    2. 5.2 Temperature
    3. 5.3 Load
    4. 5.4 Feedback Path
  8. 6 Impact on Commonly Used Circuit Configurations
    1. 6.1 Inverting Amplifier Circuit
    2.     14
    3. 6.2 Non-Inverting Amplifier Circuit
    4.     16
    5. 6.3 Buffer Circuit
    6.     18
  9. 7 Advanced Circuit Functionality Using Amplifiers With Shutdown
  10. 8 Conclusion
  11. 9 References
  12. 10Revision History

7 Advanced Circuit Functionality Using Amplifiers With Shutdown

Analog signal chains often have a variety of analog input signals that are passed to an analog-to-digital controller (ADC). Oftentimes, there are more input signals than ADC input channels available, creating the need for an input signal multiplexer. Using a dedicated multiplexer for such a role has several advantages. For example, using a MUX can be simpler, require less control signals, and allow the user the option for both voltage and current multiplexing.

However, multiplexers may require amplifiers at both their inputs and outputs. Op amps at the input of a MUX help to protect any sensors or early portions of the signal chain from MUX switching and/or charge injection. Op amps at the output of a MUX are used to provide a low-impedance voltage drive for the inputs of the ADC. Therefore, using one or more multiplexers may entail a significant increase in the number of op amps required in an analog signal chain.

Operational amplifiers with shutdown capabilities may serve as an alternative to multiplexers in such cases. Because multi-channel shutdown op amps have the ability to selectively enable and disable channels, they can effectively multiplex a signal without needing additional amplifiers at their input(s) and output(s). Circuit designers can thus reduce their overall component count. When doing so however, the potential issues caused by shoot through current and input diode clamping must be taken into account. For more information on these and other topics on the subject, see TI’s technical note on Using Operational Amplifiers as Multiplexers in Cost-Optimized Designs.