SN74HC595

Confuse me if I'm right - but should not the SN74HC595 be rather resistant for static electricity?

Yesterday I had a strange error while playing with 6 595s on a prototype board. Each 595 has 8 LEDs and an UNO is used to feed them with data. I have had the board running for a week with SER, RCLK, SRCLK and GND connected to the UNO. The SRCLR was connected to VCC. The board use a separate 5 V power supply.

I wanted to control the SRCLK from the UNO, so I was about to add a wire from an output on the UNO when I heared the windows sound that a USB connection was disconnected and all LEDs on the board "died". Note that the new wire was at this moment not connected to the 595 board.

After I did some measurement I found out that the SER input on the first 595 was broken. I could measure 5 Ohm to GND on this chip and while connected to the UNO the voltage on it when the output from the UNO was set to HIGH.

When replacing the chip everything worked again.

I did not notice any static electricity but that is the only explanation I have that have caused this.

So my question is - how fragile is the SN74HC595 for static electricity?

but should not the SN74HC595 be rather resistant for static electricity?

Ahhh, no.

So if not, what could have caused the failure? Just a bad chip?

'No', in this case, it means that the component is not strong enough to withstand static discharge. The user should avoid exposing the component to possible electrical discharges.

https://www.electronics-notes.com/articles/constructional_techniques/electrostatic-discharge/esd-effects-how-affects-electronics.php

Thanks. Then it was static electricity that killed it.

I remember back in the 70's that only cmos circuits was sensitive to static electricity but not the TTL.

Not necessarily static that killed it, but its a CMOS logic chip, its highly vulnerable to static like all of them,
which is why anti-static handling precautions should always be observed with all CMOS and MOSFET devices.

Its a given - this is why they are supplied in anti-static bags (if not, your supplier doesn't know what they
are doing).

MarkT:
Not necessarily static that killed it, but its a CMOS logic chip, its highly vulnerable to static like all of them,
which is why anti-static handling precautions should always be observed with all CMOS and MOSFET devices.

Its a given - this is why they are supplied in anti-static bags (if not, your supplier doesn't know what they
are doing).

Yes, and, companies aim for profit, and these precautions have a cost, they wouldn't spend recursus if it wasn't necessary. The problem is that the retail trade has a bad habit of storing and handling components without ESD care. Only the most expensive components receive the most attention.

People who do not have many resources to be very careful with ESD, may perhaps purchase development boards with the components already assembled, instead of free components, and avoid touching the terminals of the components, always holding by the edges of the boards away from the terminals. other than GND.

This is one of the positives of an Arduino board, instead of just buying the standalone microcontroller.

If it is necessary to approach critical points, a good practice is to always touch the GND first, to equipotentialize, this small procedure can help to avoid many problems with ESD, in case of manipulating components it is always good to avoid direct manipulation with your hands, fingers can act as spark injectors, giving preference to the use of tweezers to hold as far as possible from the critical terminals also helps to avoid problems of this nature.

Even though the component is working, it may have already received an electrostatic discharge, which has not completely damaged it, but it may have left it with some sequel, which will reduce its useful life, an abnormal heating is usually noted.

[ESD Guns | ESD Simulators Overview (Electrostatic Discharge Test)]

rtek1000:
Even though the component is working, it may have already received an electrostatic discharge, which has not completely damaged it, but it may have left it with some sequel, which will reduce its useful life, an abnormal heating is usually noted.

I agree, it is probably a cause that goes does not cross the mind.
What are you using for your bench surface, floor material, do you slide around in your chair?
Please check your mains power outlet, if it is three pin, check that you have proper earth connection.
Tom... :slight_smile:

thehardwareman:
I remember back in the 70's that only cmos circuits was sensitive to static electricity but not the TTL.

74HC595 - High speed CMOS - is not the now-obsolete TTL from whose numbering it is derived.

rtek1000:
This is one of the positives of an Arduino board, instead of just buying the standalone microcontroller.

How so?

This is one of the positives of an Arduino board, instead of just buying the standalone microcontroller.

Paul__B:
How so?

Because the Arduino board has a larger area for handling, while the microcontroller has a much smaller area for manual contact, in addition the Arduino’s own PCB helps protect the microcontroller, due to the resistivity of the material, and to the additional components.

TomGeorge:
What are you using for your bench surface, floor material, do you slide around in your chair?

Interesting, what is your point of view?

rtek1000:
in addition the Arduino's own PCB helps protect the microcontroller, due to the resistivity of the material, and to the additional components.

And that was to what I objected. The PCB is an excellent insulator and only pins 0, 1 and 13 have additional components attached. :roll_eyes:

Hi,

What are you using for your bench surface, floor material, do you slide around in your chair?

rtek1000:
Interesting, what is your point of view?

All sources of static electricity in the work place.
Tom... :slight_smile:

in addition the Arduino’s own PCB helps protect the microcontroller, due to the resistivity of the material, and to the additional components.

Paul__B:
The PCB is an excellent insulator and only pins 0, 1 and 13 have additional components attached. :roll_eyes:

Yes, but what few people know is that all materials also have a capacitive part and an inductive part. This is more a matter of telecominucations, a challenge for devices that operate at very high switching frequencies, but that can help to amortize sparks. There is no need to research much, just see that the simplest snubbers have a resistor and a capacitor.

https://learnabout-electronics.org/Semiconductors/thyristors_65.php

TomGeorge:
All sources of static electricity in the work place.

Oh boy!

Arduino user working:

Paul__B:
74HC595 - High speed CMOS - is not the now-obsolete TTL from whose numbering it is derived.
How so?

Stupid me. It should have checked the datasheet a bit better.

Still got a few old TTL from the 70's... :slight_smile: