Usually I am easy on them. This time I need to jam it pretty good and have to drive a few CD40106 inputs below GND at 1mA-2mA. TI's datasheet says 10mA is the abs max. Does anyone remember a manufacturer that might spec less than 10mA?
-- Regards, Joerg http://www.analogconsultants.com
Joerg! Joerg! Joerg! Joerg! ;-)
...Jim Thompson
-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | |
I know, I know. The topper was a design (no, not by me) where a whole uC plus periphery was supplied via one (!) port pin substrate diode. Guess they needed to save that one cent for a rectifier diode. Now that was a real white knuckle design.
-- Regards, Joerg http://www.analogconsultants.com
What is your concern, finding a CD40106 that can't take 10mA, or are you looking for a preventative measure?
Post your schematic ;-)
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
The old A series parts would SCR latch if you looked at them wrong. Pulling an input below ground would take out a power supply or some wirebonds. A few mA should be OK for a B-series part.
Can you use an HC40106? They're a lot better.
John
I 'designed by acident' a sync amp. The scenario: monitor wants composite sync at TTL level, computer delivers sync at video signal level. Monitor input is at 0 volts, no pull up resistor.
Thus, I built a little amp with a CMOS inverter. This worked but the extra power supply bothered me. Then, I switch off the power, but the thing keeps working. Hmm, there was no voltage on teh input and teh sync output is insufficient as well.
I decide to use just a decoupling cap, no power connection. Doesn't work.
I take the decoupling cap off and bing the thing works.
Must be the most ugly analog CMOS amp in existence. I suppose the monitor outputs some pull-up voltage whenever it detects a signal on the sync input. Never tried to figure it out; it worked and it was a one-off.
Thomas
"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...
I'm not sure I get this stuff......
Is that.......
Joerg! Joerg! Joerg! Joerg! ;-)
In a cheering sort of 'You Are The Man' sort of way?
Or is it a
Joerg! Joerg! Joerg! Joerg! ;-)
In a kind of 'You are such a child, let me explain it to you' sort of way?
DNA
The latter ;-)
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...
Oh.... OK.......
There you go Jeorg, e-mail Jim, but don't be a bottom boy, Texans have a problem with that stuff.
Between yourselves.
On a scale of 1 to 10 where 1 is not very cuddly and 10 is 'We are trying to explain to the wives about the lesbien type stuff'....
Something else
DNA
No, just wondering if there is a brand that specs much less. You know how that goes, purchasing finds a cheaper source and then it's like popcorn at final board test.
Since I wrote the contract myself it doesn't specify the gun type with which I'd be shot. But it kind of says that I would be :-(
-- Regards, Joerg http://www.analogconsultants.com
Can't you show us the source impedance equivalent? Then we can solve it for you ;-)
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
The uC I mentioned was a lot scarier. AFAIR the supply came from a higher voltage AC source via a resistor, could even have been 117V, don't remember. Smack dab into the port pin. Anyhow, the "regulation" so that it doesn't exceed abs max worked something like this: Bypass cap was the minimum they could get away with but large enough so the boot procedure could get a hold. Then the uC executed lots of dummy code just to burn a fairly consistent amount of milliwatts. Supposedly the dummy code was adjusted on the fly so that the MIPS levels kind of balanced out slow workload phases. Woe to the firmware programmer who didn't know this.
The way I found out was that I had to probe the oscillator. The probe's capacitance stalled it for a brief time. KAPOOF! Big crater in the uC and a puff of smoke wafting off.
-- Regards, Joerg http://www.analogconsultants.com
Yes, I remember the first generation chips. Those were the ones that gave the 4000 series such a bad rap and scared a lot of people towards TTL.
I don't remember if the 74C series was as fickle. I never had one die on me but others weren't very happy with them.
Unfortunately not here. Got to work with 12V.
-- Regards, Joerg http://www.analogconsultants.com
Joerg, how could it blow a hole in the IC? That takes more than a few watts.
If the uC only needed milliwatts to regulate the voltage, where did the extra power come from? Especially since the bypass cap was the minimum they could get away with.
There has to be some other explanation.
Regards,
Mike Monett
Antiviral, Antibacterial Silver Solution:
It's a 10uF cap on the input that is whipped around. During one phase it is pulled to -12V via a 5K resistor. I could hang a largish resistor between the cap and the CD input but I'd rather not.
It should be fine as long as the CD40106 all have the same specs.
-- Regards, Joerg http://www.analogconsultants.com
No idea. All I know is that I had a little crater in there. The bypass wasn't that small since there was a whole lot of other stuff that rode on this VCC rail. It was an electrolytic and they didn't spring an extra cent for a ceramic in parallel. Later I looked at the supply rail on a working unit and the ripple on there was nauseating.
What possibly happened is that some PWM stopped, shedding the whole load. Then the voltage crept up. This was a really old uC back from the
80's. The AC drop resistor was a big fella, maybe a watt or so. It got quite toasty.-- Regards, Joerg http://www.analogconsultants.com
I imagine all modern parts can take at least 20mA, or more, whatever spec they might put out. It's easy to test representative production parts to test reality... SCR supply breakdown is easy to observe. A limiting resistor can protect your test sample for further analysis.
--
Thanks,
- Win
Yes, Win, I did such tests a while ago. They could stomach more than
20mA. But that always leaves the nagging uncertainty about the next batch or chips from another manufacturer. Bottomline all designs here need to comply with respect to the datasheet limits. Except, of course, when doing scientific stuff like avalanching.BTW, just read a laser article (Elsevier) from Rowland. Vollmer, Fischer: "Frequency-domain displacement sensing with a fiber ring-resonator containing a variable gap". Wow, interesting things that you guys are doing over there.
-- Regards, Joerg http://www.analogconsultants.com
The CD40106BC from National does not have this maximum current specified in the datasheet at all. Ok, it's marked "discontinued", but it's still in stock at some places.
MM74C14 from Fairchild does not have it specified neither.
-- Andy
Allowing for an external Schottky diode clamp on the pcb layout would seem prudent.
App notes on 4000-series astables and monostables may give some insight into the maximum recommended negative input current whilst working.
-- Tony Williams.
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