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| * [http://uk.farnell.com/linear-technology/lt1761es5-2-5-pbf/ic-ldo-volt-reg-2-5v-0-1a-5-tsot/dp/1531492 a 2.5V, 300mV drop out, 100mA, 20V max power supply] will allow operation at 2.8V:). | | * [http://uk.farnell.com/linear-technology/lt1761es5-2-5-pbf/ic-ldo-volt-reg-2-5v-0-1a-5-tsot/dp/1531492 a 2.5V, 300mV drop out, 100mA, 20V max power supply] will allow operation at 2.8V:). |
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| ==Adjustable voltage regulators== | | ==voltage regulator== |
| These seem like they offer the voltage reqd (order of 2.5 to 2.7V) at acceptable dropout voltages - order of 0.3V.
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| But the fine print is hard to follow, so far I have investigated several families to find either I can not understand them or they have secondary voltage requirments above 4V;
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| * [http://uk.farnell.com/linear-technology/lt3080est-pbf/ic-adj-ldo-reg-0v-to-36v-1-1a-sot/dp/1556601 LT3080EST three pin regulator] requires a source voltage > 1.25V higher than output although Farnel calls it a 350mV dropout :(. 2.7+1.25 is nearly 4V, way after the LEDs have lit up. This is Farnell missing the note in the datasheet, and quoting the voltage dropout for a different part in the family.
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| * [http://uk.farnell.com/on-semiconductor/lm2931ctg/v-reg-ldo-adj-3-24v-2931-to2205/dp/1211139 LM2931CTG automotive volt regulator] This guy is just plain confusing. There are about 10 extra components in the application circuit. The guidance for selection of the output capacitor sent me of to work out the resonant freqency of tantalum caps. For which I apparently need the equivalent series inductance (ESL) - which no devices I looked at on Farnell mentioned in the datasheet, and this is the easy components. Meanwhile, I recall that I am advised to increase the size of the capacitor because the operating voltage is low.. by an unspecified amount. Next.
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| * [http://uk.farnell.com/micrel-semiconductor/mic2941awu/ic-reg-ldo-1-25a-adj/dp/1556739 MIC2941AWU automotive voltage regulator] is restricted to 4.3V inputs at temp != 25degrees. Confused? Yes, definitely. The datasheet has headline operating parameters specified for 25 degrees - that appear in the first page product blurb, and much more constrained parameters for the for the full tempreture range of -40 to +125degrees. Naturally the blurb claims the regulator operates from -40 to +125degrees. To cap it off there is no derating guidance. I am not used to datasheets being written by sales droids. Next.
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| * [http://uk.farnell.com/on-semiconductor/ncv4276adsadjg/ic-voltage-regulator/dp/1703366 NCV4276] minimum input is 4.5V - just Farnell's search tool not dealing with input voltage ranges.
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| * [http://uk.farnell.com/micrel-semiconductor/mic29152wu/ic-v-reg-ldo-1-5a-adj-smd-29152/dp/1100648 MIC29152WU 1.5A Adj] might be an ok regulator. It is 26V input continuous, 50V 10mSec spikes. 5mA minimum load. Unfortunately, the datasheet is ambiguous. The headline voltage dropout figure is 340mV, but all the electrical characteristics are quoted for 1V margin over the regulated voltage... so not sure how well it will do the job...
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| And there appears to be a better choice..
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| * [http://uk.farnell.com/linear-technology/lt3008edc-pbf/ic-adj-ldo-reg-0-6v-to-44-5v-20ma/dp/1692192 LT3008 20mA 0.6 to 44V] 200mV dropout, or 500mV at higher tempreture. Since high temp is associated with daylight or lots of wasted power this should be fine. Needs a resister network, and two caps.
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| ==digikey options..== | | ==digikey options..== |
