How to interpret this package drawing?

[Michael]

Hi - I'm trying to draw out a TO-263-5 from this datasheet:
http://www.irf.com/product-info/datasheets/data/iru1150.pdf

Thing is - it doesn't actually give dimensions - just minimum and
maximum dimensions. It doesn't even specify the actual width!! What am
I supposed to do here? Take the average of each value?

Thanks,

-Michael

 

[John Fields]

Hi - I'm trying to draw out a TO-263-5 from this datasheet:
http://www.irf.com/product-info/datasheets/data/iru1150.pdf

Thing is - it doesn't actually give dimensions - just minimum and
maximum dimensions. It doesn't even specify the actual width!! What am
I supposed to do here? Take the average of each value?

 

[John Larkin]

What's stunning is that the nominal lead pitch is not specified. So if
you guess or average to get the pitch, any error stacks up over all 5
pins! So get a sample and measure it.

And the compensation/stability guidelines suck, as is standard for
LDOs. The "Stability" paragraph is just qualitative blather.

I wouldn't use this part unless I absolutely had to.

John

 

[Eeyore]

Hi - I'm trying to draw out a TO-263-5 from this datasheet:
http://www.irf.com/product-info/datasheets/data/iru1150.pdf

Thing is - it doesn't actually give dimensions - just minimum and
maximum dimensions. It doesn't even specify the actual width!! What am
I supposed to do here? Take the average of each value?

Well..... I'd make the outline fit the max dimensions.

The tolerance on the lead pitch is puzzling though. Maybe check out the Jedec
standard for the package ? I'd take the average value myself.

Graham

 

[Michael]

What's stunning is that the nominal lead pitch is not specified. So if
you guess or average to get the pitch, any error stacks up over all 5
pins! So get a sample and measure it.

That's what really caught my eye. It's ridiculous - I've never seen
such a bad drawing. I got something hacked together that should work
though, by averaging all the values.

I found another company's drawing for TO-263-5s and they specified the
pitch as 1.7mm, which is essentially the average of the min and max
values (1.702mm).

And the compensation/stability guidelines suck, as is standard for
LDOs. The "Stability" paragraph is just qualitative blather.

I wouldn't use this part unless I absolutely had to.

I'm saving a decent amount of money going with this part though, so
the extra hassle is worth it, I hope. I don't need a particularly
smooth supply - I just need an adjustable vreg capable of taking a 5V
signal down to 3-3.5 V (adjustable) with ~200mv or less ripple, all at
about 2-3A. (constant load)

-Michael

 

[MooseFET]

Hi - I'm trying to draw out a TO-263-5 from this datasheet:http://www.irf.com/product-info/datasheets/data/iru1150.pdf

Thing is - it doesn't actually give dimensions - just minimum and
maximum dimensions. It doesn't even specify the actual width!! What am
I supposed to do here? Take the average of each value?

This looks like a design that was in inches that has been converted to
metric. Try converting the values to inches and see if a sensable
sounding number lands right near the middle of the span.

eg: 0.4" = 10.16mm. This is near the center of 10.05 and 10.668 so
there is a good chance the design started with a 0.4" dimension. I
would expect the real units to land most often just about at that
point.

 

[Jeff L]

Hi - I'm trying to draw out a TO-263-5 from this datasheet:
http://www.irf.com/product-info/datasheets/data/iru1150.pdf

Thing is - it doesn't actually give dimensions - just minimum and
maximum dimensions. It doesn't even specify the actual width!! What am
I supposed to do here? Take the average of each value?

Thanks,

-Michael

I'm short on time for details, but that is a standard 5 pin D-PAK or D-PAK2
that's been thinned out to reduce the height requirements - the pads should
be the same. The other is a standard SOIC-8.

 

[Stanislaw Flatto]

This looks like a design that was in inches that has been converted to
metric. Try converting the values to inches and see if a sensable
sounding number lands right near the middle of the span.

eg: 0.4" = 10.16mm. This is near the center of 10.05 and 10.668 so
there is a good chance the design started with a 0.4" dimension. I
would expect the real units to land most often just about at that
point.

Long time ago, when still useful in design, and constantly using metric
and 'colonial' measuring units we agreed to re-dimention the inch for
easier conversion between the decimal- binary fragments of partial
measurements. 1 inch = 25.4 mm { standard definition of inch } we
defined as 1 inch = 25.6 mm and it made the conversions more practical.
1/16" = 1.6 mm and so on ( the error is insignificant in practice as
long as you are under many inches in length dimention, and it is
_normal_ for many years to specify dimentions in mm's).

HTH

Stanislaw

 

[Spehro Pefhany]

That's what really caught my eye. It's ridiculous - I've never seen
such a bad drawing. I got something hacked together that should work
though, by averaging all the values.

I found another company's drawing for TO-263-5s and they specified the
pitch as 1.7mm, which is essentially the average of the min and max
values (1.702mm).

It's also the same as IRF's drawing for the TO-262 (1.700 mm nominal),
as you can see from this package drawing:

http://www.irf.com/package/cic/5pto262po.pdf

It's laid out with proper GD&T tolerancing-- the numbers in boxes are
"basic" dimensions that are theoretically exact, and the position of
each lead is defined off the 'A' datum in the maximum material
condition so you can easily figure worst case conditions.

It would be tempting to guess that the nominal dimension is the same
as the SDIP pitch of 1.778mm nominal (0.070"), but it'snot.

I'm saving a decent amount of money going with this part though, so
the extra hassle is worth it, I hope. I don't need a particularly
smooth supply - I just need an adjustable vreg capable of taking a 5V
signal down to 3-3.5 V (adjustable) with ~200mv or less ripple, all at
about 2-3A. (constant load)

-Michael

Best regards,
Spehro Pefhany

 

[John Larkin]

Long time ago, when still useful in design, and constantly using metric
and 'colonial' measuring units we agreed to re-dimention the inch for
easier conversion between the decimal- binary fragments of partial
measurements. 1 inch = 25.4 mm { standard definition of inch } we
defined as 1 inch = 25.6 mm and it made the conversions more practical.
1/16" = 1.6 mm and so on ( the error is insignificant in practice as
long as you are under many inches in length dimention, and it is
_normal_ for many years to specify dimentions in mm's).

HTH

Stanislaw

In the early days of IC design, when mask patterns were cut from
rubylith, an inch was defined as 25 mm.

John

 

[John Fields]

What's stunning is that the nominal lead pitch is not specified.

---
Yeah, it is, but I was wrong about "average"

For the TO-263 package the pitch is the sum of half of the
difference between the max and the min and the min of "G". IOW:

1.829 - 1.575
pitch = --------------- + 1.575 = 1.702mm
2

 

[Spehro Pefhany]

---
Yeah, it is, but I was wrong about "average"

For the TO-263 package the pitch is the sum of half of the
difference between the max and the min and the min of "G". IOW:

1.829 - 1.575
pitch = --------------- + 1.575 = 1.702mm
2

One nice thing about the GD&T (eg. ASME Y14.5M or ISO) method of
tolerancing (as on the other IRF drawing I linked to) compared to
coordinate tolerancing is that there is no build-up of tolerances. The
theoretically exact "basic dimension" is given and the position of
each pin is specified to lie within a certain tolerance zone. To get
the same effect with coordinate tolerancing you'd either have to put a
stupidly tight tolerance on the pitch, dimension every pin, or add
some kind of note to the drawing.


Best regards,
Spehro Pefhany

 

[YD]

Late at night, by candle light, John Fields

---
Yeah, it is, but I was wrong about "average"

For the TO-263 package the pitch is the sum of half of the
difference between the max and the min and the min of "G". IOW:

1.829 - 1.575
pitch = --------------- + 1.575 = 1.702mm
2

a - b
Let's write that as ------- + b which we then can write as
2

a - b + 2b a + b
---------- = -------
2 2

Sure looks like an arithmetic average to me.

- YD.

 

[Bertie the Bunyip]

Well..... I'd make the outline fit the max dimensions.

The tolerance on the lead pitch is puzzling though. Maybe check out
the Jedec standard for the package ? I'd take the average value
myself.

Hey pooh pooh, why you going around behind my back looking for software
to wreck a froup? You know I'll do it for frei!


Bertie