Other Parts Discussed in Thread: PGA460, PGA308
Tool/software:
I filtered the list on the TI webstire for PGAs & VGAs and it seemed like the PGA117 has many of these features such as hardware/software shutdown, daisy chaining, and cost it cannot autonomously utilize a lookup table or internal set of control registers to adjust gain over time without continuous microcontroller (MCU) intervention so I could use more advice if this is the best product fit. It would be nice to have a custom gain profile saved to the PGA or even a linear/curved gain profile saved on board which is not a requirement but would be a nice to have. Unforunately a AGC will not work for my application, it must be TVG. I'm looking for something that has similar functionality or better to the TVG in the PGA460 but I don't want to use the PGA460 for this application.
Core Requirements:
- Programmable TVG Curve: Ideally, the TVG should have control registers or another programmable method to define the gain line/curve, allowing it to operate autonomously after an initial configuration. If there's another way to accomplish this with external circuity so the MCU can sleep that's an option too.
- Minimal MCU Involvement: The MCU should only need to set up the gain profile once, or update it periodically, rather than actively controlling the gain in real-time.
- Cost Target: Preferably a max $10-$15 range. I looked at AFEs but they are significantly more expensive but that's an option too
- Gain Range: TBD, but similar applications use 32 dB to 90 dB. If a single TVG stage doesn’t provide sufficient gain, I’m open to cascading two stages.
Application Details:
- Input Signal: Single-ended input from a Piezo transducer used for water sensing (can make it differential if needed)
- Output: Single-ended preferred (but differential is possible if required). The TVG output will be fed into a 0-3.3V ADC.
- Power Constraints: Battery-powered system with a 3V to 4.2V supply range.
- Low-Power Operation: The system receives signals for only 20ms at 1-2 Hz, with everything else in sleep mode to maximize power efficiency. The TVG should allow the MCU to remain in deep sleep for as long as possible.
- Operating Frequency: Currently ~40 kHz, though this could increase in future iterations.
Nice-to-Have Features:
- Enable/Disable Control: A dedicated enable pin would be useful to conserve power, but I could use a FET to switch ground if needed as long as I don't have to rewrite the gain values and account for startup time.
- Voltage-Controlled Alternative: If no register-controlled TVG is available, I could consider a voltage-controlled option but would prefer to avoid the complexity of external timing circuits in order to keep the MCU sleeping.
I’d appreciate any recommendations on suitable TI parts that meet these requirements. Thanks!
