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Help with power supply design for portable device

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  1. Jan 7, 2013 #1
    I need help designing a power supply for a portable medical research device for animals. My problem is designing a configuration for multiple voltages with pcb size and power efficiency in mind. I need 3.3 V, +/- 1.5 V, and +/- 20 V.

    Below I’ve listed device info and estimated current consumption of both the analog and digital components.

    Device Info: My device will be worn by small rodents and used to (1) amplify low-voltage and low frequency (< 15 kHz) analog signals, (2) output 100uA@20V constant current pulses, and (3) communicate with PC via BT. This device will be small (2’x2’ double sided pcb) and light weight. Thus, efficiency and pcb footprint are extremely important. Component cost isn’t much of a concern.

    Digital Components:
    1. MCU: 10 mA @ 3.3 V (Supply Range: 1.7 - 5.0 V )
    2. Bluetooth Module: 15 mA @ 3.3V (Supply Range: 3.0 - 3.6 V, peak current 50mA)

    Analog Components: All analog components use dual power supplies (+/-).
    1. Section A: 1mA @ +/- 1.5 V (<1% duty cycle, Supply Range: 1.0 - 3.3 V)
    2. Section B: 2mA @ +/- 20.0 V (1% duty cycle)

    Battery: I was hoping to use a 3.6 V LiPo battery unless there is a more appropriate battery or source voltage.

    Questions: Where and how should I use LDO, switching, or linear regulators together for this application? What’s the best way to get the +/- 20 V? Should I adjust any component supply voltages for higher efficiency? ... etc...? Any help would be tremendously appreciated.
     
    Last edited: Jan 7, 2013
  2. jcsd
  3. Jan 8, 2013 #2
    There are several free on-line or downloadable design/simulators specifically for power supplies. I'm sure you will need to balance overall weight/size/power consumption, and simulations can be helpful in quickly running numerous design iterations to compare results.

    A few to get you started:
    http://www.ti.com/ww/en/analog/webench/power.shtml
    http://www.poweresim.com/
    http://www.fairchildsemi.com/design_tools/

    Don't forget that switching supplies may introduce noise in your data sampling circuits.
     
  4. Jan 9, 2013 #3

    dlgoff

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    Science Advisor
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    Big rodents. :devil:
     
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