PGA460-Q1: Device setting and some other questions

Hi Shiyu,

1. The order at which Burst Pulses, Current Limit, Digital Gain and TVG are set doesn’t matter as long as they are set before the burst and listen operations are initiated. The following video provides an example of configuring these parameters: https://training.ti.com/pga460-ultrasonic-sensing-how-set-and-install-evm?context=1128182-1128152

2. The current limit feature is mainly for transformer-driven modules and is a way of controlling the peak-to-peak driver voltage at the transducer. Generally, the larger the driver current limit at the primary side of the transformer, the larger the excitation voltage swing at the secondary (transducer) side of the transformer, which would result in a stronger signal.  Adjusting the pulse count affects the transducer excitation length and also results in a stronger echo strength, regardless of whether a direct-driven or transformer-driven module is used. Sections 5.2 and 5.3 of the below application note provides more info on how pulses and the current limit affects the echo strength: https://www.ti.com/lit/an/slaa732a/slaa732a.pdf

3. The data-dump memory on the device stores a maximum of 128 bytes. Echo data is down sampled to allow capturing of the complete recording interval. The down sampling amount depends on the record time-length parameter for the preset of interest set by the P1_REC and P2_REC bits in the REC_LENGTH EEPROM register. During the process of down-sampling, a peak hold function is performed and therefore only the highest level values after down-sampling are stored in the data-dump memory. If you need more than 128 samples for a burst period, another option is to use direct data burst mode, which is described in Section 7.3.7.2 of the PGA460 datasheet.
4. You can enable this by performing the following steps:
   1. Clicking the “Log UMR” checkbox (circled in blue below) in the data monitor tab.
   2. Clicking “Start” (circled in red below).
   3. Clicking on the “Utilities tab on the bottom right”. The results will be in the “Datalog” textbox (circled in green below).  If you want to export this to a text file, you can click the “Save” button below the Datalog screen.
   4. 

5. There isn’t an exact formula for the decay time.  We recommend using the ultrasonic measurement results to view the decay time and then tune the system to reduce this decay time based on your short-range sensing requirements.  The below video has more info on how to perform this tuning:

   https://training.ti.com/ti-precision-labs-ultrasonic-sensing-ultrasonic-transducer-tuning?context=1139747-1139746-1147829-1147821

Regards,

Mekre