PGA460-Q1: Peak Hold in PGA460-Q1

Part Number: PGA460-Q1
Other Parts Discussed in Thread: PGA460

Hi team,

I 'm designing Low pass filter coefficients.(I understand PGA460 calculates LPF coefficients automatically. However, I would like to set them by myself.)

To test effects of low pass filter, I need to simulate the Peak Hold processing before LPF processing.

Question:

How long are the values held in the Peak Hold before low pass filter in Digital signal processing?

Thank you.

over 4 years ago

0 Scott Bryson over 4 years ago

TI__Mastermind 20980 points

Thank you for your continued interest in PGA460. Please refer to the description of the Peak Hold in the response below

https://e2e.ti.com/support/sensors/f/sensors-forum/870536/pga460-pga460-coefficients-bandpass

Thank you,

Scott Bryson

0 tr over 4 years ago in reply to Scott Bryson

Prodigy 220 points

Hi Scott ,

Thank you for your usual help.

I read the thread you show.

However, this "Peak Hold" seem to mean the processing from the signal after LPF to echo data dump(128byte).

What I would like to know is "Peak Hold" before LPF.

If this "Peak Hold" is before LPF, I will recognize that maximum value during PeakHoldTime( = PresetRecLenTime/128) is held.

Is this correct?

regards,

0 Scott Bryson over 4 years ago in reply to tr

TI__Mastermind 20980 points

The Peak Hold timing specified would be for the block preceding the LPF, and should be variable based on PresetRecLenTime.

0 tr over 4 years ago in reply to Scott Bryson

Prodigy 220 points

Hi Scott ,

>and should be variable based on PresetRecLenTime.

Thanks.

May I understand that the longer the preset recording time, the lower the distance resolution?

For example, when PeakHoldTime is 512μs(PresetRecLenTime=65.536ms), the distance resolution will be 8.7cm(=340m/s×512μs/2).

Also. is the signal after PeakHold still at sampling frequency 1MHz?

Does not it became a 1,953.125Hz(=128sample/65.536ms) signal?

regards,

0 Scott Bryson over 4 years ago in reply to tr

TI__Mastermind 20980 points

Yes, for longer preset recording time there will be lower distance resolution.

The echo dump is always 128 bytes, and this downsample rate is only applicable to this result. The ultrasonic measurement result always uses the ADC sample rate of 1us downsample equivalent, which is much better resolution than the echo data dump.

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PGA460-Q1: Peak Hold in PGA460-Q1