LTC6244 - Peak detector (hold time)

Hi,

About the "Improved Peak Detector" available here:

https://www.analog.com/en/technical-articles/ltc6244-high-speed-peak-detector.html

Demo Circuit: https://www.analog.com/media/en/simulation-models/LTspice-demo-circuits/LTC6244_PeakDetector_Improved.asc

I would like to measure the DC with an voltmeter, so the holding time must be, at least, 3~5 seconds, and the LTSpice show me a holding time of only 1~2 ms.

I tried increase the capacitor (C1) value, as well R4 and R6, but with no success.

May someone give me a help about how to increase the holding time to 3~5 seconds?

Thanks in advance,

Renato

  • +1
    •  Analog Employees 
    on Oct 18, 2018 4:55 PM over 2 years ago

    Hi Renato,

    3-5 seconds is a very long time for any sample-hold circuit. One thing you could do is replace R4 with a low-leakage analog switch (or JFET), which you could use to reset C1 to zero, then open to capture a new peak value.

    But D2 reverse leakage would be a problem - you could replace D2 and D3 with a diode-connected JFETs. This may reduce the accuracy, and you would want to match the forward drops of D2 and D3 accordingly.

    Another point - does your end application really using a handheld voltmeter, or is this an intermediate step in your development, to eventually be replaced with an integrated circuit ADC, with data either being displayed, or captured by a host computer? If the latter, consider skipping the voltmeter, and use a low-cost microcontroller platform that has an onboard ADC for this step. Even an Arduino Uno might do the job, you could use it to control the reset / capture operation of the circuit, digitize the sample-hold output, and display either to a computer connected via USB serial port, or to an LCD screen.

    This might be a good starting point:

    https://www.arduino.cc/en/Tutorial/ReadAnalogVoltage

    -Mark

  • Dear Mark,

    Thank you for your support!

    I was thinking to use it with a handheld voltmeter.

    Now, with your suggestion, I will use arduino to storage the peaks in a SD Card and show the max value in a LCD screen.

    Thank you!

    Renato