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MAX14662 voltage peaks when switch open

Category: Hardware
Product Number: MAX14662

Hello,

I chose the MAX14662 for a project I am currently working on.

During testing, I noticed an issue: when I run a signal through one of the 8 switches of the component in an open state, voltage peaks appear at the rising and falling edges of my signal.

As shown in the diagram, my signal is a series of 1 ms-long pulses with a 500 mV amplitude and a frequency of 50 Hz. When the switch is closed, the signal passes through unhindered. However, when the switch is open, I observe voltage peaks at the edges of the signal. These peaks have an amplitude of about 72 mV. I also noticed that with larger signal amplitudes, the peaks increase proportionally.

Setup details:

  • Signal source: Function generator
  • Connection: Signal passes through one of the switches of the MAX14662 and into an oscilloscope.
  • Control: The switch is driven via SPI using an Arduino.

These peaks could significantly influence the final signal in my project, so I need to address them. Here are my questions:

  1. What could be causing these peaks? Could it be due to capacitive coupling between the switch's input and output?
  2. Can these peaks be avoided or mitigated without affecting the primary signal?
  3. If this phenomenon is unavoidable, could you recommend any alternative components better suited for this application?

Your input and recommendations would be greatly appreciated!

Parents
  • Hi  ,

    The voltage peaks in your signal are likely caused by capacitive coupling due to the parasitic capacitance between the input and output of the MAX14662 switch. This phenomenon is common in analog switches, particularly when the input signal has sharp edges, and the output is connected to a high-impedance load. When the switch is open, transient currents induced by the high dv/dt of the input signal can couple through the parasitic capacitance, creating the observed voltage spikes at the output.

    To address this issue, you can add a pull-down or pull-up resistor (e.g., 10 kΩ) at the output to provide a discharge path for the coupled energy. Alternatively, a small capacitor (10 pF to 100 pF) at the output can absorb the transient spikes, smoothing the signal. If your application allows, reducing the rise and fall times of the input signal by adding a series resistor and small capacitor at the input can also help. Proper PCB layout, such as isolating high-speed signals and improving shielding, can further minimize parasitic coupling.

    If these mitigation strategies are insufficient, Analog Devices offers several switches designed with low parasitic capacitance and leakage that are better suited for high-precision applications. The ADG5412 is an excellent choice, featuring ultralow capacitance and low charge injection, making it ideal for minimizing coupling effects in sensitive circuits. Another option is the ADG1604, a quad 4:1 multiplexer with low capacitance and high bandwidth, designed for precise signal routing with minimal distortion.

    Both devices provide improved performance over standard analog switches and can significantly reduce unwanted coupling in your application.

    Let me know if you need assistance with additional specifications or implementation guidance for these components.

    Regards,

    Gelo

Reply
  • Hi  ,

    The voltage peaks in your signal are likely caused by capacitive coupling due to the parasitic capacitance between the input and output of the MAX14662 switch. This phenomenon is common in analog switches, particularly when the input signal has sharp edges, and the output is connected to a high-impedance load. When the switch is open, transient currents induced by the high dv/dt of the input signal can couple through the parasitic capacitance, creating the observed voltage spikes at the output.

    To address this issue, you can add a pull-down or pull-up resistor (e.g., 10 kΩ) at the output to provide a discharge path for the coupled energy. Alternatively, a small capacitor (10 pF to 100 pF) at the output can absorb the transient spikes, smoothing the signal. If your application allows, reducing the rise and fall times of the input signal by adding a series resistor and small capacitor at the input can also help. Proper PCB layout, such as isolating high-speed signals and improving shielding, can further minimize parasitic coupling.

    If these mitigation strategies are insufficient, Analog Devices offers several switches designed with low parasitic capacitance and leakage that are better suited for high-precision applications. The ADG5412 is an excellent choice, featuring ultralow capacitance and low charge injection, making it ideal for minimizing coupling effects in sensitive circuits. Another option is the ADG1604, a quad 4:1 multiplexer with low capacitance and high bandwidth, designed for precise signal routing with minimal distortion.

    Both devices provide improved performance over standard analog switches and can significantly reduce unwanted coupling in your application.

    Let me know if you need assistance with additional specifications or implementation guidance for these components.

    Regards,

    Gelo

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