Determining correct IC part number from Eagle schematic (and in general)

[dtbingle]

My current project involves a Nano, an adafruit microSD breakout board, and an MCP2515 CAN breakout board. The breadboard version works great and now I'm looking to combine all of these elements onto a single PCB.

Schematics for both the adafruit microSD and generic MCP2515 CAN boards are available, but I'm somewhat overwhelmed trying match the labeled IC in Eagle vs. the actual IC components to purchase.

For example, on the adafruit microSD Eagle schematic, the logic level shifter IC used is labeled as "4050D". After a few searches, adafruit has an article discussing it and mentions that it uses the "CD74HC4050". Great. But even then, when you search CD74HC4050 in mouser, there are about 20 versions that come up. Obviously some vary by footprint, surface mount vs. through hole and packaging, but that still leaves a few variants to choose from.

How do you determine which variant to choose? Many of these part #'s vary by the suffix only, but there doesn't seem to be an industry standard for this naming, usually only within each manufacturer.

[system]

I wouldn't worry about it . They are going to be equivilent to the typical part, the CD4050BE

datasheet

What's the issue ?

[dtbingle]

No real issue (yet). Doing this for work and the approval chain for ordering items is painful. In other words, trying to avoid ordering variant A, find out it doesn't work, then have to go through process again to spend $5 for variant B.

This is my first go at doing something like this and not hugely familiar with what small differences need to be considered in this application.

But for example, the datasheet you posted is for CD4050B. I was planning to buy this (link - Toshiba 74HC4050D(BJ)). They appear very similar, but with slightly different footprint, propogation times, voltage handling, etc. I'm assuming either would work fine, but it's difficult to wade through all of this with little experience.

[system]

They appear very similar,

Then I would guess you have little or no experience with CMOS.
I say that because anyone who used CMOS back in the day used the CD4049 and C4050 all the time to
interface their CMOS circuits with their TTL circuits. (this is what the data sheet is referring to when it says:

High-to-Low Level Logic Conversion

It's practically impossible to have CMOS experience
and not be familiar with the CD4049 & CD4050. Most everybody made sure they always had a couple of
each on hand.

these devices are used for logic-level conversions. These devices are intended for use as CMOS to DTL or TTL converters

They are only similar in layout.
Try looking at the power supply voltage specs.
The one I linked is rated to run up to 20V.D
The one you linked is designed for 5V (but they put 7V as the absolute maximum but it means 5V.
That's why I never use those.
The one I linked is a TTL to CMOS converter IC. (and therefore is designed to interface 12V to 18V CMOS
with 5V TTL)

The one you linked is simply a buffer and nothing more.
Apples and oranges. (both are fruit but only one of them can make orange juice)

[dtbingle]

With the input voltage being supplied from the arduino +5v pin, is there any reason to have a higher input voltage limit on the IC?

[system]

With the input voltage being supplied from the arduino +5v pin, is there any reason to have a higher input voltage limit on the IC?

Are you referring to the Vcc pin ?

Why are you even using the CD4050 anyway if you're using 5V logic ?

First of all, I never said anything about the input voltage. I said the Power Supply specs were different.
And second, the decision to use a CD4050 is not based on the arduino voltage. It's usually based on
the voltage of the circuitry you want to interface to. (like 15V CMOS).

I don't have your schematic so I can't answer that. The CD4050 is for interfacing 12V or 15V CMOS with 5V TTL. If you want to send a transistor on/off signal to a power transistor on the ceiling of a 200Foot movie studio to control the neon lights in a special effect lighting , you're not going to use 5V TTL. You're going to use 12V to 18V CMOS because it will still work at the end of a 100 cable run from the lights down to the floor of the studio. The CD4050 would , for example, be used between a 5V processor and the CMOS drive signal. This project was done in 1982 and used all discrete logic and analog switches , so there was no 5V logic used in this circuit, but IF you wanted to send an arduino control signal 100 feet, you couldn't send it as a 5V TTL signal. You would need to convert it to a 12V to 18V CMOS signal to get it there and you could downconvert it at the receiving end in need be.

[DVDdoug]

In industry there are several documents and the schematic doesn't show everything. In fact, the schematic is an "engineering document" not needed for production.

There is a bill of materials (BOM) that has the reference designators (R1, etc.), an "internal" part number, a description (which may or may not have a partial manufacturer's number), quantity used (R1 & R5 may be the same part), and there's a line/item number sometimes referenced on the assembly drawing for hardware or other non-electrical parts.

Then there's a "parts master" and/or "approved parts list" with the actual approved manufacturer's part numbers associated with each internal part number. Whenever possible there are usually approved parts from more than one manufacturer so you're not locked-into one source. Copies of the manufacturer's datasheets are usually associated with the approved parts list.

The buyer uses the approved parts list when ordering parts.

[system]

adafruit-micro-sd-breakout-board

Did you see this ?
(namely the part where it says:

For the level shifter we use the CD74HC4050

Not sure why the microsd card needs a buffer but apparently that's all it is.

[dtbingle]

Yes, that's the exact schematic imported into my Eagle project.....to be used for a microSD card buffer.

From past experience with a cheaper microSD breakout card WITHOUT the buffer, it causes issues when using it with other devices also on the SPI bus. For example, trying to read CAN data from a vehicle with MCP2515 breakout board and reading microSD data at the same time had issues. The SPI lines were held captive by the non-buffered microSD inputs and wouldn't allow the CAN chip to transmit data.

And yes, that adafruit post lists that the "CD74HC4050" is used. But you go and search on mouser for "CD74HC4050", 11 results show up with a different suffix CD74HC4050xxxx. In the datasheet, the table at the top lists different suffixes with varying IC size/packaging, but are there any major functional differences?

[system]

but are there any major functional differences?

No, or it would not be listed on the same datasheet. That's the whole point of standardization.
Only the form is different, not the function.
If the function is different it won't be on the same datasheet.

Also, if it has the same base part number (ie:74HC4050) then the logic function has to be the same.
The only differences will be in speed, power supply voltage, temperature rating, package size etc.
but they will all speak the same logic language and will have compatible pinouts.

[dtbingle]

Got it, that makes sense. Thanks for the info/help!

[dl324]

dtbingle:
For example, on the adafruit microSD Eagle schematic, the logic level shifter IC used is labeled as "4050D".

A 4xxx part number without a prefix would be assumed to be CD (or possibly MC14xxxx, or HEF4xxx). All three would have the same electrical function; though there are some exceptions.

After a few searches, adafruit has an article discussing it and mentions that it uses the "CD74HC4050". Great. But even then, when you search CD74HC4050 in mouser, there are about 20 versions that come up.

This is one of my gripes about part numbers. A CD4050 operates from 3-18V, 74HC operate from 2-6V. Parts labeled CD74HC just cause confusion. What family are they? CD4xxx or 74HC?

there doesn't seem to be an industry standard for this naming, usually only within each manufacturer.

I blame it on clueless manufacturers. I have some parts labeled 74HCTLS. 74HCT has TTL inputs and CMOS outputs, 74LS is TTL inputs and outputs. I have no idea what 74HCTLS is supposed to be.

[system]

I have no idea what 74HCTLS is supposed to be.

I'm going to take a wild guess:

Low Power Schottky with TTL inputs and CMOS outputs ?

[westfw]

You'll tend to see two types of schematics.

1. Over-specified "Industry Professional" schematics that will happily tell you that a component is an "ROHM SML-D121LWT86" and "Diodes Inc 74LVC1T45FW4-7" when what you really wanted to know is "any 0603 sized (English) yellow SMT LED" and "nearly anyone's single-gate 3.3/5V translator." As DVDDoug said, this is what's used when engineering has to pass a design on to a separate manufacturing team. There's usually some discussion as to what parts are allowable substitutes, and bad things can happen when some purchasing guy decides "hey, look at this great deal I got on 20MHz crystals for the ethernet board - all 20MHz crystals are about the same, right?" (to mention a real example...)

2. Under-specified "generic" schematics that will say things like "4050" or "15 ohm resistor" when they mean "I used a 74hc4050" and "you realize this is a 1W resistor from the size of the package on the PCB, right?" Common in hobbyist and open source designs.

A good schematic will have some additional explanation ("generic 0603 resistor", "Must be NXP 74hct4050B for correct operation", but usually a LACK of specification means that you really don't need to pay much attention to the details. (I pretty consistently put "Rled" on LED current limiting resistors; you're supposed to figure our the exact value you want based on which LED you used, how bright you want it to be, and how much power you're willing to use up. And "Cbyp" for bypass caps, too: "somewhere between about 0.01 and 1uF; whatever you've got...")

Not sure why the microsd card needs a buffer but apparently that's all it is.

the xxxx4050 is a level-shifting buffer; It's used to convert the 5V Arduino signals to 3.3V SD signals.
(the 4050 is actually dual-supply, so it'll convert almost anything to almost anything. Especially the older CD4050 chips that would run over the full pure-CMOS voltage range.)

[dl324]

raschemmel:
I'm going to take a wild guess:

Low Power Schottky with TTL inputs and CMOS outputs ?

Seeing that you were just guessing, I decided to educate myself.

There are CMOS processes that combine bipolar and CMOS devices (called BiCMOS), HCT isn't one of them. The input is CMOS, but they scaled the width of the devices to shift the threshold voltage to be TTL compatible.

For HC devices, the P device width is twice the N device width. This ratio was the defacto "standard" until somewhere around the 90nm node when the drive strength of P devices was improved to match N devices (devices used for HCT circa 1996 were on a 3000nm node; microprocessors of that era were at 250nm).

For HCT devices, they reduced the P device width as much as they could and increased the width of the N device. The ratio went from 2:1 (P:N) for HC to around 1:8 for HCT; according to a layout I found.

Samsung intended for their 74HCTLS parts to be drop-in replacements for 74LS with no performance penalty. But it's a CMOS process.

[system]

Since we're in the EDUCATE mode here:

In your last post (Reply-14) you said this:

There are CMOS processes that combine bipolar and CMOS devices (called BiCMOS), HCT isn't one of them. The input is CMOS, but they scaled the width of the devices to shift the threshold voltage to be TTL compatible.

which is exactly OPPOSITE of what you said in Reply#-11:

I have some parts labeled 74HCTLS. 74HCT has TTL inputs and CMOS outputs,
74LS is TTL inputs and outputs. I have no idea what 74HCTLS is supposed to be.

On Page-8 of this Toshiba document :

Table 2.1 shows each series and the input level.
Table 2.1 Series Definition

is says this:

HCT TTL level input of HC series

Regarding your comment:

I have no idea what 74HCTLS is supposed to be

This is from the Samsung document on 74HCTLS:

Both fammes feature TTL input voltage levels which enable them to interface with all TTL, NMOS or CMOS outputs without any external components

is from this Samsung document (presumably the SAME one YOU used as a reference)

1988_Samsung_High_Performance_CMOS_Logic_Data_Book

This seems to match what you said in Reply#11

74HCT has TTL inputs[/i] and CMOS outputs,

I have never studied HCT series Ics because I have always simply used a CD4050BE

Take note of this on Page-1:

The
input-signal high level (VIH) can exceed the VCC
supply voltage when these devices are used for logiclevel conversions. These devices are intended for use
as CMOS to DTL or TTL converters

and the Supply Voltage specs on Page-4:

Supply voltage VCC to VSS –0.5 20 V

In plain English, what that means is that the OUTPUT logic level is determined by Vcc.
so if the OUTPUT = 5V TTL, then Vcc = 5V, and the INPUT voltage level MAY exceed that.
If , on the other hand, the OUTPUT is 15V CMOS, then Vcc = 15V and the INPUT must
be the same logic level so these chips are strictly CMOS-to-TTL but not vice versa.

To do that you need a CD4504
Note on page-1 it says"
the CD4504 consists of six circuits which shift input signals from the Vcc logic level to the Vdd
logic level. Simply put, connect 5V to the Vcc to tell the chip the inputs are 5V TTL and
connect 15V to Vdd to tell the chip the outputs are 15 CMOS.

That being said, if you keep CD4050s and CD4504 on hand , you can handle any situation that
comes along.

Personally, I never found HCT to be much use because of the supply voltage limitations.
You can't use them for 12V or 15V applications (like the project I mentioned in Reply#5).

Operating Voltages of HCT Circuits
HCT circuits feature a limited operating voltage range due to the fact that they have to work with TTL voltage levels. Since
internal switching layout is equivalent to HC circuits (with the exception of the input stage), these components could be
operated from a 2-V to 6-V range. For HCT circuits operating at less than 4.5 V, the load-level noise margin is reduced and
becomes incompatible with TTL thresholds, thus losing one of the primary advantages of the HCT devices.

74HCT Logic Family Applications and Restrictions