I am building a custom Atmel Mega 2560 PCB that will run off the 9V 600mAh rechargeable li-ion batteries in a bus. I need to supply - 5V for MCU and other components in PCB, the overall current consumption being 2000mA. I use Arduino Mega 2560 before with XBEE wireless and some sensors, the board fail to deliver the require power so that’s why I want to design my own custom board with some change in components.

The is more than one type of Voltage Regulators, I use Digi key website as an electronics wiki to discover electronic elements and components and I see these type of voltage regulators:-

  1. PMIC - Voltage Regulators - DC DC Switching Controllers
  2. PMIC - Voltage Regulators - DC DC Switching Regulators
  3. PMIC - Voltage Regulators - Linear
  4. PMIC - Voltage Regulators - Linear + Switching
  5. PMIC - Voltage Regulators - Linear Transistor Driver
  6. PMIC - Voltage Regulators - Special Purpose

Mega 2560 use NCP1117ST50T3G to drive 9v to 5v with 800mA output current There is another AVR board based on Arduino Mega 2560 call Freaduino Mega2560 and its use MP2307 as a voltage regulator this chip is not linear voltage regulator like NCP1117ST50T3G which used it original Mega 2560 its DC DC Switching Regulators and its provide 5v with 2000mA output current but it’s use many pins not like linear regulators and I read in Digi Key it has frequency can someone explain the difference between DC DC Switching Regulators and not linear voltage regulator.

I continue my search in Digi key and custom my search for 5v, 3A output current in Voltage Regulators and find these items


My questions are as follows:

  1. If I use any one of these 3A regulator in my circuit will it heat up or not.

  2. Is it safe if I use Two 9V battery 600mA and connect it in parallel mode to increase the ampere to 1200mA will this work fine with regulator or these batteries with their output current will not enough to provide 5v with 3A output current.

  3. Do I need to use heat sink or not?

  4. last not least can someone explain the purpose and usage or these type of voltage regulator which I've listed it above and which type is the perfect for MCU board.

Thank you very much for your help.

  • \$\begingroup\$ Pfff, you ask way too much in one question ! Some things you can easily find yourself like linear vs switched regulators. If you do not know what you need Digikey shows you too much info. Instead look for ready made modules like ones based on LM2596 chip. \$\endgroup\$ – Bimpelrekkie Feb 9 '16 at 15:00
  • \$\begingroup\$ Dear FakeMoustache 2 you could skip my last question, what about use one of these 3A voltage regulator in my circuit and answer my first three question. \$\endgroup\$ – Haider Feb 9 '16 at 15:04
  • \$\begingroup\$ that's why I love this site because of your answer I understand many things thank you very much for every one comment and answer in this question, Now I'll focus on switching voltage regulator but there are many manufactures and type so please could you give me link about question asked before how to use them and choice the right capacitor for them I really want to try them using Multisim simulation. \$\endgroup\$ – Haider Feb 9 '16 at 16:37
  1. DO NOT Use a linear voltage regulator if you need more current than your source can effecfively provide. A linear voltage regulator is basically just a self-adjusting resistor that "burns off" any voltage higher than it is set for.
  2. You should be looking for a "buck converter" that's capable of the voltage and current you need.
  3. Make sure to add a large capacitor (at least several uF) between the regulator's output & GND. This will reduce the "frequency" you're concerned about.
  4. The buck converter should heat up much less than your linear did; using a heatsink might still be necessary though. Test and decide.
  5. Yes, you can parallel 2 9V batteries, but may want to shunt resistor them if using rechargables (you can search this site for plenty of other questions about parallel batteries).
  • \$\begingroup\$ what about chips in this link \$\endgroup\$ – Haider Feb 9 '16 at 15:32
  • \$\begingroup\$ digikey.com/product-search/en/integrated-circuits-ics/… \$\endgroup\$ – Haider Feb 9 '16 at 15:32
  • \$\begingroup\$ It's linear voltage regulator and produce 3A output current but they don't say how much input current from 9v you need \$\endgroup\$ – Haider Feb 9 '16 at 15:33
  • \$\begingroup\$ Those are still linear (controlled resistance) regulators. To get 3A out, they need 3A in, and to convert 9Vx3A to 5Vx3A they "burn" 4Vx3A=12W wasted power as heat...thet would require a large heatsink to not burn a hole through your PCB! \$\endgroup\$ – Robherc KV5ROB Feb 9 '16 at 16:01
  • \$\begingroup\$ This one looks promising: digikey.com/product-detail/en/AP1506-50K5G-13/… \$\endgroup\$ – Robherc KV5ROB Feb 9 '16 at 16:17
  1. Yes. Those regulators you linked are linear regulators. (Switching regulators can heat up too, but we'll leave that for another time.)

  2. Drawing 600mA from a 9V makes for a very sad (and short-lived) 9V, at least for a standard 9V (an Energizer 522 capacity is <400mAh @ 500mA discharge rate). Much better to use a stack of AA batteries (much higher current capacity).

  3. At 2A, you are dissipating 2A*(9V-5V)=8W. Yes, you need a well-designed thermal plane (the datasheet can tell you how to calculate temperature rise). You cannot just put a heatsink on top of a DDPAK, the thermal resistance through the top of the case is not good.

  4. This is too broad of a question. You have linked linear low dropout regulators. There is no single "perfect" regulator type. To second FakeMoustache: given your experience level, if you want to use a switching regulator, you should buy an existing module (designing a switching regulator into a board requires considerably more domain knowledge than does a linear regulator).

  • \$\begingroup\$ there is 600mA 9v battery its EBL 600mAh 9 Volt Li-ion Rechargeable \$\endgroup\$ – Haider Feb 9 '16 at 15:50
  • \$\begingroup\$ this question really make me think again about 9v battery \$\endgroup\$ – Haider Feb 9 '16 at 15:57
  • \$\begingroup\$ 600mAh is not the same as 600mA. You can try drawing 600mA, but the capacity will probably be greatly reduced. And even if the battery has the same capacity at high discharge rates, you will only be able to run your device for an hour at best. \$\endgroup\$ – uint128_t Feb 9 '16 at 16:00

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