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Task: Make a reliable power supply for sensors and an RFID card reader.

Specifications:

  1. Total current consumption: up to 0.7A (700 mA.)
  2. Elements supply voltage: 3.3V
  3. Input voltage: 5V
  4. Working temperature: from -30 to + 40

For these purposes, I found the AMS1117 voltage regulator.

The technical description indicates the use of tantalum capacitors.

I studied them, and I still had doubts about their reliability.

What I learned:

  1. Tantalum minimally changes the capacitance with a change in voltage and temperature, unlike ceramic capacitors.
  2. Tantalum does not age
  3. Makes no sound
  4. May explode in case of strong impulse or incorrect polarity.
  5. It has a high parasitic inductance, unlike ceramics.

Many boards with this voltage regulator use ceramic capacitors, but I'm not sure about the reliability of this option.

I worry that tantalum may explode or fail.

Questions:

  1. Is it dangerous to use tantalum and is it worth switching to ceramics?
  2. Is it good to use electrolytic capacitors, given the negative operating temperatures?
  3. I heard that special voltage regulators have appeared, designed to work with ceramic capacitors. What are some good options? The current must be up to 1A.

My main task is to provide reliable power to the sensors and reader.

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This may help you. I am currently working with the voltage regulator LD11173v3 and I actually run some tests with it. I am using the recommendations of design of this circuit and the output seems to be pretty stable. I am working with high freq signals so mi picture results are not suitable for you now but I tested the performance with inputs from 3 to 10 volts and 100mA to 1000 mA.

https://www.sparkfun.com/datasheets/Components/LD1117V33.pdf

I tested this circuit with tantalum capacitors and the look to be stable. Temperature effect has not been tested so I cannot tell you anything in this issue. Let's say what other's say, buy if you want to try that component it's up to you! :)

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  • \$\begingroup\$ Thanks for the advice, I will try two options: AMS1117 with ceramics and a resistor. And your version with LD1117 tantalum capacitor. :) \$\endgroup\$ – Алекс Гарисон May 18 at 12:13
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I suggest you use a ceramic capacitor with a small resistor in series equivalent to the ESR of a similar size tantalum capacitor. That's on the output, of course, there's no reason for the resistor on the input capacitor.

That gives you the stability (as guaranteed as you'll ever get) and none of the disadvantages of tantalum caps, at the virtually negligible cost of a single resistor.

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  • \$\begingroup\$ Thanks for the answer! I made a preliminary scheme. \$\endgroup\$ – Алекс Гарисон May 18 at 11:54
  • \$\begingroup\$ Thanks for the answer! I create circuit. imgur.com/ct6llQy I studied the ESR of several tantalum capacitors suitable for capacitance and voltage. Values ​​are as follows: 4 ohms, 3 ohms, 1.8 ohms. What value should I choose? \$\endgroup\$ – Алекс Гарисон May 18 at 12:04
  • \$\begingroup\$ 3.3\$\Omega\$ is probably good. \$\endgroup\$ – Spehro Pefhany May 18 at 12:06
  • \$\begingroup\$ Thank you very much!!! \$\endgroup\$ – Алекс Гарисон May 18 at 12:11

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