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Turning on the heater introduces a voltage spike and voltage swing on my 3.3V regulator and this causes a transimpedance amplifier output to be wrong.

Every time the heater turns on my 3.3V regulator voltage changes by +-5mV. Note: 12V and 5V regulator voltage also change.

Heater MCH2-80W-001 datasheet

I have tried all below methods but did get any improvement. I need be able to avoid the voltage swing as much as possible.

  1. Add MOV or varistor parallel to the heater
  2. Add inrush current limiter in series to the heater
  3. Add MOV and ICL
  4. Add diode in parallel to the heater

Below diagram is just for demonstration, actual circuit will have all bypass and require parts.

schematic

The following graph shows when the heater turns on and off (red circles.)

enter image description here

schematic

simulate this circuit – Schematic created using CircuitLab

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  • \$\begingroup\$ What do you mean when you say that the output of the 3.3V regulator changes by 5mV? Is it a 5mV ripple on top of 3.3VDC? 5mV may well be within the specs for that regulator. What part numbers are your regulators? \$\endgroup\$ – vir Nov 10 '20 at 17:23
  • \$\begingroup\$ Is it noise on the 3.3v or does the regulated level change? Show the amp circuit. Why is it so sensitive to the supply rail? \$\endgroup\$ – Aaron Nov 10 '20 at 17:57
  • \$\begingroup\$ @Vir 3.3V Regulator voltage output change by 5mV. Ex: 3.28V to 3.35V every time the heater turns on and off. Regulator MIC5353-3.3YMT \$\endgroup\$ – Shahreza Nov 10 '20 at 18:26
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    \$\begingroup\$ I meant, why is the amplifier so sensitive to the supply rail? Post the amplifier schematic. \$\endgroup\$ – Aaron Nov 10 '20 at 18:31
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    \$\begingroup\$ The TL2426 used as a reference is why the amplifier is sensitive to the power supply change because it is always going to be half of the supply. So if the supply moves around, your reference will move around. You could try a fixed reference instead. Something like a TL431. \$\endgroup\$ – Aaron Nov 10 '20 at 18:54

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