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<div dir="ltr">Hi Paul,</div><div dir="ltr"><br clear="none"></div><div dir="ltr">To answer your question about minimum input voltage, you need to think about Vdropout.</div><div dir="ltr"><br clear="none"></div><div dir="ltr">You apply a Vin and expect the Linear Regulator to provide Vout. Vdifference (Vin - Vout) is dropped across the pass element inside the regulator which works like a variable "resistor." This is why the linear regulator while small, simple, and quiet can be very inefficient (short battery life).</div><div><br clear="none"></div><div dir="ltr">Ex. Vin 9V, Vout 5V, Vdifference = 4V<br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">44.4% of the power is consumed by the regulator (4 / 9)</div><div dir="ltr"><br clear="none"></div><div dir="ltr">As the input drops (battery), the efficiency increases until Vdifference approaches Vdropout. Vdropout is a function of load current and specific regulator. In the LDO you mention, Vdropout is 100mV at a current of 100mA. This is an effective dropout resistance of 1 ohm.</div><div dir="ltr"><br clear="none"></div><div dir="ltr">When Vdifference <= Vdropout, the regulator is no longer regulating. It becomes a fixed in-line resistor between the battery and the load about 1 ohm in this case.</div><div dir="ltr"><br clear="none"></div><br><div dir="ltr">Sincerely,<br clear="none"></div><div dir="ltr">Kevin S.<br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr"><br clear="none"></div><div><br clear="none"></div></div><div class="ydpbfc982bbyiv4283235404ydp32ad6ed1yahoo_quoted" id="ydpbfc982bbyiv4283235404ydp32ad6ed1yahoo_quoted_6218646841">
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On Sunday, November 15, 2020, 7:47:19 PM EST, Josh Wyatt via TriEmbed <triembed@triembed.org> wrote:
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<div><div id="ydp1fee312yiv4283235404ydp32ad6ed1yiv9239802742"><div><div dir="ltr">Why not use something like AMS1117-3.3? Minimum voltage on your 8 volt battery is going to be something like 6VDC.<br clear="none"><div><br clear="none"><div>-j</div></div></div><br clear="none"><div class="ydp1fee312yiv4283235404ydp32ad6ed1yiv9239802742gmail_quote"><div class="ydp1fee312yiv4283235404ydp32ad6ed1yiv9239802742yqt9316888523" id="ydp1fee312yiv4283235404ydp32ad6ed1yiv9239802742yqt19625"><div class="ydp1fee312yiv4283235404ydp32ad6ed1yiv9239802742gmail_attr" dir="ltr">On Sun, Nov 15, 2020 at 7:38 PM The MacDougals via TriEmbed <<a shape="rect" href="mailto:triembed@triembed.org" rel="nofollow" target="_blank">triembed@triembed.org</a>> wrote:<br clear="none"></div><blockquote class="ydp1fee312yiv4283235404ydp32ad6ed1yiv9239802742gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex;"><div lang="EN-US"><div class="ydp1fee312yiv4283235404ydp32ad6ed1yiv9239802742gmail-m_-940597067329552067WordSection1"><p class="ydp1fee312yiv4283235404ydp32ad6ed1yiv9239802742MsoNormal">How do I find an LDO that operates on 8 – 8.8 v?<u></u><u></u></p><p class="ydp1fee312yiv4283235404ydp32ad6ed1yiv9239802742MsoNormal">I looked at a couple of datasheets and found linear regulators that take 9v (max) input.<u></u><u></u></p><p class="ydp1fee312yiv4283235404ydp32ad6ed1yiv9239802742MsoNormal">I did not see a (min) spec for input v.<u></u><u></u></p><p class="ydp1fee312yiv4283235404ydp32ad6ed1yiv9239802742MsoNormal"><u></u> <u></u></p><p class="ydp1fee312yiv4283235404ydp32ad6ed1yiv9239802742MsoNormal">How can I tell if it works at 8?<u></u><u></u></p><p class="ydp1fee312yiv4283235404ydp32ad6ed1yiv9239802742MsoNormal"><u></u> <u></u></p><p class="ydp1fee312yiv4283235404ydp32ad6ed1yiv9239802742MsoNormal">For example:<u></u><u></u></p><p class="ydp1fee312yiv4283235404ydp32ad6ed1yiv9239802742MsoNormal"><a shape="rect" href="https://www.njr.com/electronic_device/PDF/NJM2888_E.pdf" rel="nofollow" target="_blank">https://www.njr.com/electronic_device/PDF/NJM2888_E.pdf</a><u></u><u></u></p><p class="ydp1fee312yiv4283235404ydp32ad6ed1yiv9239802742MsoNormal"><u></u> <u></u></p><p class="ydp1fee312yiv4283235404ydp32ad6ed1yiv9239802742MsoNormal"><u></u> <u></u></p><p class="ydp1fee312yiv4283235404ydp32ad6ed1yiv9239802742MsoNormal">---> Paul<u></u><u></u></p><p class="ydp1fee312yiv4283235404ydp32ad6ed1yiv9239802742MsoNormal"><u></u> <u></u></p></div></div>_______________________________________________<br clear="none">
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</blockquote></div></div></div></div><div class="ydp1fee312yiv4283235404ydp32ad6ed1yqt9316888523" id="ydp1fee312yiv4283235404ydp32ad6ed1yqt45526">_______________________________________________<br clear="none">Triangle, NC Embedded Computing mailing list<br clear="none"><br clear="none">To post message: <a shape="rect" href="mailto:TriEmbed@triembed.org" rel="nofollow" target="_blank">TriEmbed@triembed.org</a><br clear="none">List info: <a shape="rect" href="http://mail.triembed.org/mailman/listinfo/triembed_triembed.org" rel="nofollow" target="_blank">http://mail.triembed.org/mailman/listinfo/triembed_triembed.org</a><br clear="none">TriEmbed web site: <a shape="rect" href="http://TriEmbed.org" rel="nofollow" target="_blank">http://TriEmbed.org</a><br clear="none">To unsubscribe, click link and send a blank message: mailto:<a shape="rect" href="mailto:unsubscribe-TriEmbed@bitser.net" rel="nofollow" target="_blank">unsubscribe-TriEmbed@bitser.net</a>?subject=unsubscribe<br clear="none"><br clear="none"></div></div></div></body></html>