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I am working on a senior project and I have been tasked with the battery and power supply, and I am a newbie to power.

This will be an "iPad" sort of device, so ideally, we want a built-in battery that will power multiple components and have the ability to charge via wall outlet, or USB.

We have three main components to power: a touchscreen monitor (+12 VDC for backlight, +5 VDC for monitor), an FPGA (+7 - 15 VDC), and a microcontroller (+3.3 - 5 VDC). What is the best approach to this?

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    \$\begingroup\$ start writing an input output specs with range and tolerances defined for each port including power consumption and variations expected then define discharge and charge times to determine battery capacity and charger capacity, .. just for starters \$\endgroup\$ – Sunnyskyguy EE75 Oct 18 '16 at 3:59
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    \$\begingroup\$ …what kind of FPGA runs on 15V?! \$\endgroup\$ – duskwuff Dec 18 '16 at 1:40
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A lithium pack of 4S or 14.8V. Regulate down to 12V and 5V. Switch up the charging voltage as needed. Or take a look at existing devices with the same needs. Any number of iPad information, or Android tablet reference designs. A dedicated PMU, power management unit may be ideal. Look at Texas Instruments website for some ideas.

Also see if the back light can work at a lower voltage, and you may get away with a 3s battery instead.

Edit:

All iPads use multiple parallel cell 1S Lipo setups. In that case, you regulate the input voltage down and regulate the output up for 5V and 12V. Like any typical usb power bank, reference designs are everywhere.

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    \$\begingroup\$ All tablets I know of use 1S architecture. Easy to manage. \$\endgroup\$ – Ale..chenski Oct 18 '16 at 4:10
  • \$\begingroup\$ @AliChen I forgot about that. But other devices use multiple combinations. Lenovo tablets or laptops, any number of android tablets. \$\endgroup\$ – Passerby Oct 18 '16 at 4:24
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First of all you have to know the characteristics of your system:

  • voltage range and tolerances
  • max current
  • min operating time
  • max charging time
  • requirements for battery type (LiPo, Li-ion etc.) there are restrictions for certain industries
  • max dimensions
  • Any other requirements e.g. like switching off voltages individually is necessary
  • costs

Only then you can decide what your final design will look like, whether you will use switched power supplies or linear regulators.

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