What might this term (N sub C) be, calculating ripple current for a buck converter output capacitor?
I'm reading through the datasheet for TI's TPS54302 step-down converter, and determining values for support components.
There is a calculation to determine ripple current for the output capacitor which is:
$$
I_{COUT(RMS)} = frac{1}{sqrt12} times left(
frac{V_{OUT}times(V_{IN(MAX)}-V_{OUT})}
{V_{IN(MAX)} times L_{OUT} times f_{SW} times N_C} right)
$$
(Where $L_{OUT}$ is the inductor value (H), $f_{SW}$ is the switching frequency (Hz).)
I'm not sure what the term $N_C$ is meant to be.
Looking around online, other formulas omit this. For example, in this document by Rohm titled Capacitor Calculation for Buck Converter IC, page 4 has the formula:
$$
I_{CO} = frac{1}{sqrt12} times left(
frac{V_{OUT}(V_{IN(MAX)}-V_{OUT})}
{L times f_{SW} times V_{IN(MAX)}} right)
$$
Either I am ignorant of what $N_C$ is in this context (the datasheet doesn't clarify); the term is optional depending on application; or TI has a mistake in the datasheet.
What is $N_C$ in this case?
capacitor buck ripple-current
asked yesterday
JYeltonJYelton
15.9k2889190
add a comment |
I'm reading through the datasheet for TI's TPS54302 step-down converter, and determining values for support components.
There is a calculation to determine ripple current for the output capacitor which is:
$$
I_{COUT(RMS)} = frac{1}{sqrt12} times left(
frac{V_{OUT}times(V_{IN(MAX)}-V_{OUT})}
{V_{IN(MAX)} times L_{OUT} times f_{SW} times N_C} right)
$$
(Where $L_{OUT}$ is the inductor value (H), $f_{SW}$ is the switching frequency (Hz).)
I'm not sure what the term $N_C$ is meant to be.
Looking around online, other formulas omit this. For example, in this document by Rohm titled Capacitor Calculation for Buck Converter IC, page 4 has the formula:
$$
I_{CO} = frac{1}{sqrt12} times left(
frac{V_{OUT}(V_{IN(MAX)}-V_{OUT})}
{L times f_{SW} times V_{IN(MAX)}} right)
$$
Either I am ignorant of what $N_C$ is in this context (the datasheet doesn't clarify); the term is optional depending on application; or TI has a mistake in the datasheet.
What is $N_C$ in this case?
capacitor buck ripple-current
asked yesterday
JYeltonJYelton
15.9k2889190
add a comment |
I'm reading through the datasheet for TI's TPS54302 step-down converter, and determining values for support components.
There is a calculation to determine ripple current for the output capacitor which is:
$$
I_{COUT(RMS)} = frac{1}{sqrt12} times left(
frac{V_{OUT}times(V_{IN(MAX)}-V_{OUT})}
{V_{IN(MAX)} times L_{OUT} times f_{SW} times N_C} right)
$$
(Where $L_{OUT}$ is the inductor value (H), $f_{SW}$ is the switching frequency (Hz).)
I'm not sure what the term $N_C$ is meant to be.
Looking around online, other formulas omit this. For example, in this document by Rohm titled Capacitor Calculation for Buck Converter IC, page 4 has the formula:
$$
I_{CO} = frac{1}{sqrt12} times left(
frac{V_{OUT}(V_{IN(MAX)}-V_{OUT})}
{L times f_{SW} times V_{IN(MAX)}} right)
$$
Either I am ignorant of what $N_C$ is in this context (the datasheet doesn't clarify); the term is optional depending on application; or TI has a mistake in the datasheet.
What is $N_C$ in this case?
capacitor buck ripple-current
asked yesterday
JYeltonJYelton
15.9k2889190
I'm reading through the datasheet for TI's TPS54302 step-down converter, and determining values for support components.
There is a calculation to determine ripple current for the output capacitor which is:
$$
I_{COUT(RMS)} = frac{1}{sqrt12} times left(
frac{V_{OUT}times(V_{IN(MAX)}-V_{OUT})}
{V_{IN(MAX)} times L_{OUT} times f_{SW} times N_C} right)
$$
(Where $L_{OUT}$ is the inductor value (H), $f_{SW}$ is the switching frequency (Hz).)
I'm not sure what the term $N_C$ is meant to be.
Looking around online, other formulas omit this. For example, in this document by Rohm titled Capacitor Calculation for Buck Converter IC, page 4 has the formula:
$$
I_{CO} = frac{1}{sqrt12} times left(
frac{V_{OUT}(V_{IN(MAX)}-V_{OUT})}
{L times f_{SW} times V_{IN(MAX)}} right)
$$
Either I am ignorant of what $N_C$ is in this context (the datasheet doesn't clarify); the term is optional depending on application; or TI has a mistake in the datasheet.
What is $N_C$ in this case?
capacitor buck ripple-current
capacitor buck ripple-current
asked yesterday
JYeltonJYelton
15.9k2889190
asked yesterday
JYeltonJYelton
15.9k2889190
asked yesterday
JYeltonJYelton
15.9k2889190
asked yesterday
JYeltonJYelton
15.9k2889190
asked yesterday
JYeltonJYelton
15.9k2889190
15.9k2889190
add a comment |
add a comment |
1 Answer
1
active
oldest
votes
Most likely, number of capacitors.
If you make your (for example) 100 uF output capacitance using three 33-uF capacitors in parallel, then the ripple current each one needs to handle is only 1/3 of the total ripple current.
(Even though it doesn't look like the parameter is ever explained, nor is the possibility of multiple parallel capacitors discussed, the text immediately above the equation talks about the current for "each capacitor", implying that in some draft the author had the idea of using multiple capacitors, even if this didn't make it into the final version of the datasheet)
answered yesterday
The PhotonThe Photon
83.6k396194
The data sheet doesn't say that $N_C$ is the number of output capacitors, but the schematic has two, and the text says that equation 15 gives the equation "for each capacitor". Bad technical writing style, there TI, to not name all your variables!
– TimWescott
yesterday
Very intuitive thinking to understand other engineers with so-so math skills.
– Sparky256
21 hours ago
In equation 9 (Page 15) they use the formula in question to derive IL(Max) and it appears they use a value of 0.8 for Nc, Am I missing something?
– Tyler
15 hours ago
add a comment |
Your Answer
StackExchange.ifUsing("editor", function () {
return StackExchange.using("mathjaxEditing", function () {
StackExchange.MarkdownEditor.creationCallbacks.add(function (editor, postfix) {
StackExchange.mathjaxEditing.prepareWmdForMathJax(editor, postfix, [["\$", "\$"]]);
});
});
}, "mathjax-editing");
StackExchange.ifUsing("editor", function () {
return StackExchange.using("schematics", function () {
StackExchange.schematics.init();
});
}, "cicuitlab");
StackExchange.ready(function() {
var channelOptions = {
tags: "".split(" "),
id: "135"
};
initTagRenderer("".split(" "), "".split(" "), channelOptions);
StackExchange.using("externalEditor", function() {
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled) {
StackExchange.using("snippets", function() {
createEditor();
});
}
else {
createEditor();
}
});
function createEditor() {
StackExchange.prepareEditor({
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: false,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: null,
bindNavPrevention: true,
postfix: "",
imageUploader: {
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
},
onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
});
}
});
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2felectronics.stackexchange.com%2fquestions%2f415780%2fwhat-might-this-term-n-sub-c-be-calculating-ripple-current-for-a-buck-convert%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
Most likely, number of capacitors.
If you make your (for example) 100 uF output capacitance using three 33-uF capacitors in parallel, then the ripple current each one needs to handle is only 1/3 of the total ripple current.
(Even though it doesn't look like the parameter is ever explained, nor is the possibility of multiple parallel capacitors discussed, the text immediately above the equation talks about the current for "each capacitor", implying that in some draft the author had the idea of using multiple capacitors, even if this didn't make it into the final version of the datasheet)
answered yesterday
The PhotonThe Photon
83.6k396194
The data sheet doesn't say that $N_C$ is the number of output capacitors, but the schematic has two, and the text says that equation 15 gives the equation "for each capacitor". Bad technical writing style, there TI, to not name all your variables!
– TimWescott
yesterday
Very intuitive thinking to understand other engineers with so-so math skills.
– Sparky256
21 hours ago
In equation 9 (Page 15) they use the formula in question to derive IL(Max) and it appears they use a value of 0.8 for Nc, Am I missing something?
– Tyler
15 hours ago
add a comment |
Most likely, number of capacitors.
If you make your (for example) 100 uF output capacitance using three 33-uF capacitors in parallel, then the ripple current each one needs to handle is only 1/3 of the total ripple current.
(Even though it doesn't look like the parameter is ever explained, nor is the possibility of multiple parallel capacitors discussed, the text immediately above the equation talks about the current for "each capacitor", implying that in some draft the author had the idea of using multiple capacitors, even if this didn't make it into the final version of the datasheet)
answered yesterday
The PhotonThe Photon
83.6k396194
The data sheet doesn't say that $N_C$ is the number of output capacitors, but the schematic has two, and the text says that equation 15 gives the equation "for each capacitor". Bad technical writing style, there TI, to not name all your variables!
– TimWescott
yesterday
Very intuitive thinking to understand other engineers with so-so math skills.
– Sparky256
21 hours ago
In equation 9 (Page 15) they use the formula in question to derive IL(Max) and it appears they use a value of 0.8 for Nc, Am I missing something?
– Tyler
15 hours ago
add a comment |
Most likely, number of capacitors.
If you make your (for example) 100 uF output capacitance using three 33-uF capacitors in parallel, then the ripple current each one needs to handle is only 1/3 of the total ripple current.
(Even though it doesn't look like the parameter is ever explained, nor is the possibility of multiple parallel capacitors discussed, the text immediately above the equation talks about the current for "each capacitor", implying that in some draft the author had the idea of using multiple capacitors, even if this didn't make it into the final version of the datasheet)
answered yesterday
The PhotonThe Photon
83.6k396194
Most likely, number of capacitors.
If you make your (for example) 100 uF output capacitance using three 33-uF capacitors in parallel, then the ripple current each one needs to handle is only 1/3 of the total ripple current.
(Even though it doesn't look like the parameter is ever explained, nor is the possibility of multiple parallel capacitors discussed, the text immediately above the equation talks about the current for "each capacitor", implying that in some draft the author had the idea of using multiple capacitors, even if this didn't make it into the final version of the datasheet)
answered yesterday
The PhotonThe Photon
83.6k396194
answered yesterday
The PhotonThe Photon
83.6k396194
answered yesterday
The PhotonThe Photon
83.6k396194
answered yesterday
The PhotonThe Photon
83.6k396194
83.6k396194
The data sheet doesn't say that $N_C$ is the number of output capacitors, but the schematic has two, and the text says that equation 15 gives the equation "for each capacitor". Bad technical writing style, there TI, to not name all your variables!
– TimWescott
yesterday
Very intuitive thinking to understand other engineers with so-so math skills.
– Sparky256
21 hours ago
In equation 9 (Page 15) they use the formula in question to derive IL(Max) and it appears they use a value of 0.8 for Nc, Am I missing something?
– Tyler
15 hours ago
add a comment |
The data sheet doesn't say that $N_C$ is the number of output capacitors, but the schematic has two, and the text says that equation 15 gives the equation "for each capacitor". Bad technical writing style, there TI, to not name all your variables!
– TimWescott
yesterday
Very intuitive thinking to understand other engineers with so-so math skills.
– Sparky256
21 hours ago
In equation 9 (Page 15) they use the formula in question to derive IL(Max) and it appears they use a value of 0.8 for Nc, Am I missing something?
– Tyler
15 hours ago
The data sheet doesn't say that $N_C$ is the number of output capacitors, but the schematic has two, and the text says that equation 15 gives the equation "for each capacitor". Bad technical writing style, there TI, to not name all your variables!
– TimWescott
yesterday
The data sheet doesn't say that $N_C$ is the number of output capacitors, but the schematic has two, and the text says that equation 15 gives the equation "for each capacitor". Bad technical writing style, there TI, to not name all your variables!
– TimWescott
yesterday
Very intuitive thinking to understand other engineers with so-so math skills.
– Sparky256
21 hours ago
Very intuitive thinking to understand other engineers with so-so math skills.
– Sparky256
21 hours ago
In equation 9 (Page 15) they use the formula in question to derive IL(Max) and it appears they use a value of 0.8 for Nc, Am I missing something?
– Tyler
15 hours ago
In equation 9 (Page 15) they use the formula in question to derive IL(Max) and it appears they use a value of 0.8 for Nc, Am I missing something?
– Tyler
15 hours ago
add a comment |
Thanks for contributing an answer to Electrical Engineering Stack Exchange!
- Please be sure to answer the question. Provide details and share your research!
But avoid …
- Asking for help, clarification, or responding to other answers.
- Making statements based on opinion; back them up with references or personal experience.
Use MathJax to format equations. MathJax reference.
To learn more, see our tips on writing great answers.
Some of your past answers have not been well-received, and you're in danger of being blocked from answering.
Please pay close attention to the following guidance:
- Please be sure to answer the question. Provide details and share your research!
But avoid …
- Asking for help, clarification, or responding to other answers.
- Making statements based on opinion; back them up with references or personal experience.
To learn more, see our tips on writing great answers.
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2felectronics.stackexchange.com%2fquestions%2f415780%2fwhat-might-this-term-n-sub-c-be-calculating-ripple-current-for-a-buck-convert%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
