Connect with us

GSM GPRS Modem Power Supply From Alkaline Batteries

Discussion in 'Electronic Design' started by Tom Harris, Jul 10, 2013.

Scroll to continue with content
  1. Tom Harris

    Tom Harris Guest

    Greetings,

    Got a requirement for a GSM/GPRS modem to run off alkaline cells, which is a little unusual, as they are designed to run straight from a Lithium-Polymer battery at about 3.6V. A common power specification for modems is 3.3v -4.6V at a few mA standby, 50mA active with 500us bursts every 5ms up to 1.5A(!) when transmitting.

    As I said I need alkaline cells to run this from. What do people think to running the modem from 3x cells 4.5V nominal, 4.8V max with new cells on light load via a silicon diode to drop .7V to keep the volts below the maximumfor the modem. When the cells discharge a bit below 3.8V say, the diode isswitched out with a latching relay.

    I don't care about wasting the power in the diode as the modem is switched on only for a few seconds every week, so the power lost is minimal.

    Thanks for any ideas

    TomH
     
  2. miso

    miso Guest

    Normally I like LDOs with PMOS pass devices, but if you go LDO in this
    case, I'd probably go with a bipolar LDO. There isn't much voltage to
    turn on the PFET when it goes out of regulation.

    Alkalines have a linear drop to about half a volt a cell, but you really
    need to buck/boost if you are only using a few cells.
     
  3. use an LDO, pick one with enable and you also have you on-off switch

    you could try and find an example of a usb gsm mode, usb is 5V and
    limited to 500mA so the supply must handle the voltage and the burst
    current


    -Lasse
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-