Need help selecting inductor for boost regulator.
hi guys,
i'm working on little regulator board can boost 5v 12v , switched on , off. need output 3w (250ma) peak power.
for board have selected regulator, which, according convenient schematic 5-12v boost, appears able handle current need:
http://www.ti.com/lit/ds/symlink/lm27313.pdf
i found datasheet detailing layout of regulator's evalulation board:
http://www.ti.com/lit/an/snva066a/snva066a.pdf
(the evaluation board datasheet says it's lm2731, regulator part of family of regulators have different power output capabilities, , use same components in schematics. they're interchangeable.)
anyway, i've gone through components , selected appropriate substitutes suggested, except one... inductor. don't know lot inductors, having never used them before, want make sure select appropriate one.
the datasheet evaluation board lists one:
http://parts.digikey.com/1/parts/641224-power-inductor-10uh-4-0a-smd-cdrh125-100mc.html
but digikey doesn't carry it, , don't know how costs. can see though rated 10uh 20%, 4a, 25mohm dcr, , 100c max temp. shielded, , believe has ferrite core, i'm not that.
i use inductor work lm2731 shown on evaluation board in case decide later need use beefier regulator.
here datasheet lm2731 btw:
http://www.ti.com/lit/ds/symlink/lm2731.pdf
if used regulator, 6w max output should correspond 500ma @ 12v seems lot lower 4a rating on inductor suggested. , if @ page 13 shows x model's load current when boosting 5v 12v maxes out around 600ma, still far less 4a rating on inductor suggested.
but, if calculations on page 12 see peak current if output 500ma , duty cycle 62.5%, 1.42a. , though higher, still below current rating of inductor suggested. (it indicate me though should choose current rating of inductor based on input current rather output... calculate 1.5a 5v input 500ma @ 12v output. that's close 1.42a equation gave me.)
so, want know need inductor can handle 4a, or 1 can handle 2a do? , 1 here, can handle 3a? fine?
http://search.digikey.com/us/en/products/nr8040t100m/587-2001-1-nd/1739113
also, how's dc resistance , self resonant frequency on look? datasheet doesn't seem specify range of values these should within, i'm not sure if appropriate values or not. notice dc resistance bit higher part recommended don't know how matters. don't know if resonant frequency important. i'm guessing there's important relation between , frequency @ boost regulator pwm.
oh, , reason chose particular inductor it's surface mount, ferrite core, shielded, 10uh, dcr didn't seem high, , current rating pretty close 1 suggested. digikey has ton of them in stock , among cheapest available. i'd prefer not choose part have less 2k in stock.
i'm working on little regulator board can boost 5v 12v , switched on , off. need output 3w (250ma) peak power.
for board have selected regulator, which, according convenient schematic 5-12v boost, appears able handle current need:
http://www.ti.com/lit/ds/symlink/lm27313.pdf
i found datasheet detailing layout of regulator's evalulation board:
http://www.ti.com/lit/an/snva066a/snva066a.pdf
(the evaluation board datasheet says it's lm2731, regulator part of family of regulators have different power output capabilities, , use same components in schematics. they're interchangeable.)
anyway, i've gone through components , selected appropriate substitutes suggested, except one... inductor. don't know lot inductors, having never used them before, want make sure select appropriate one.
the datasheet evaluation board lists one:
http://parts.digikey.com/1/parts/641224-power-inductor-10uh-4-0a-smd-cdrh125-100mc.html
but digikey doesn't carry it, , don't know how costs. can see though rated 10uh 20%, 4a, 25mohm dcr, , 100c max temp. shielded, , believe has ferrite core, i'm not that.
i use inductor work lm2731 shown on evaluation board in case decide later need use beefier regulator.
here datasheet lm2731 btw:
http://www.ti.com/lit/ds/symlink/lm2731.pdf
if used regulator, 6w max output should correspond 500ma @ 12v seems lot lower 4a rating on inductor suggested. , if @ page 13 shows x model's load current when boosting 5v 12v maxes out around 600ma, still far less 4a rating on inductor suggested.
but, if calculations on page 12 see peak current if output 500ma , duty cycle 62.5%, 1.42a. , though higher, still below current rating of inductor suggested. (it indicate me though should choose current rating of inductor based on input current rather output... calculate 1.5a 5v input 500ma @ 12v output. that's close 1.42a equation gave me.)
so, want know need inductor can handle 4a, or 1 can handle 2a do? , 1 here, can handle 3a? fine?
http://search.digikey.com/us/en/products/nr8040t100m/587-2001-1-nd/1739113
also, how's dc resistance , self resonant frequency on look? datasheet doesn't seem specify range of values these should within, i'm not sure if appropriate values or not. notice dc resistance bit higher part recommended don't know how matters. don't know if resonant frequency important. i'm guessing there's important relation between , frequency @ boost regulator pwm.
oh, , reason chose particular inductor it's surface mount, ferrite core, shielded, 10uh, dcr didn't seem high, , current rating pretty close 1 suggested. digikey has ton of them in stock , among cheapest available. i'd prefer not choose part have less 2k in stock.
hm, see why 1 particular inductor cheap. it's pretty large. 8mmx8mm. i'd prefer use bit smaller.
Arduino Forum > Using Arduino > Motors, Mechanics, and Power (Moderator: fabioc84) > Need help selecting inductor for boost regulator.
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