4
\$\begingroup\$

Which parameter in this data sheet is the default current flowing from the input to the ground regardless of the load current?

In my case an 12V input will be regulated to 5V by the TL780-05. So to estimate the total power dissipation I will use the following formula:

Preg = (I_n × 12) + (I_load × (12-5))

My problem is I don't know how they name I_n in the regulator datasheets, so I got stuck. Where in the datasheet I can find I_n? And is that always named same way?

\$\endgroup\$
10
\$\begingroup\$

This is the one:

enter image description here

So typically 5 mA, maximum 8 mA

How to quickly find that: I know it's a current so I look for any parameter specified in A (or mA, uA) in the UNIT column. Then I look at each and see if that could be the one.

There will be a small increase with increasing load current, see the line under the red rectangle.

\$\endgroup\$
5
\$\begingroup\$

In that particular data sheet, they seem to be calling it "Input Bias Current". A more common term is "Quiescent Current".

\$\endgroup\$
2
\$\begingroup\$

It's called input bias current and is on page 3 of the data sheet you linked.

\$\endgroup\$
1
\$\begingroup\$

In most cases you can ignore this bias current as it is small enough.

What you should be concerned about is voltage drop on regulator multiplied by load current.

For example if you have 12V input, 5V output and expected load current 3A - the power dissipation on regulator equial

P = (12-5)*3 = 7*3 = 21W

Load will take P = 5V*3A = 15W (41.2%) with power loss of 21W (58.3%) -- the circuit is very inefficient, produces a lot of heat and requires bulky radiator.

If your circuit is not critical to some power 'noise' then solution based on LM2596, LM2576, MP1484, MP1584, MP2307 is more desirable due higher efficiency.

Of course you are not limited by these ICs and can use any other DC-DC converter.

MPS, TI, ST RENESAS, ON, INFINEON

DIGIKEY, MOUSER, 10 Best Electronics Suppliers

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.