But it's just an opamp. 80c for a single is a bit much for this design ;-)
-- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
Several buck converters. The others can all sense in the ground lead. And yes, I can and probably will have to voltage-derate.
-- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
The reason the part is'nt widely availiable is because it's relatively new.
Newark didnt even buy a whole reel. I book marked it as soon as it was stocked.
I ussually just use zetex HS current sensors but this one caught my intrest because it has at least some internal protection.
I dont understand why a vendor would pay a large distrubutor to stock a component? Why wouldnt he just deal directly with LT?
yuk, 0603! I'll have to use two of these monsters (manual cal).
with this client
0402 is easy. 0201, well... we'll see-- Thanks, Fred.
Mine was $1095 :-(
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
Stormy on the East Coast today... due to Bush\'s failed policies.
LOL!
I've just received a bunch of Maxim's emails with this footnote:
LEAD-TIME ACCURACY IMPROVED The lead times cited in the purchasing section of our website are now more accurate. Previously, the times shown were often longer than reality. Now, lead times are more precise and reliable...
Does that mean that they've succeeded in matching the lead time to what was previously displayed?
Maxim have just released one part that would fit the bill and simplify my life but, don't know why, I'm very reluctant to design it in. And yes, I have the samples right under my nose, but all other solutions would have to prove to be not viable before I even think using it.
-- Thanks, Fred.
Did that include the post-op anesthesia?
Nope. That was $15.95/bottle ;-)
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
Stormy on the East Coast today... due to Bush\'s failed policies.
Sans crown? Ouch!
-- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
I use the little Veho USB microscope when soldering those. It leaves enough distance from the viewed object to wield the Weller with an ETS tip in there.
-- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
Here is a single chip solution for your problem: INA203/204/205. MSOP-10
-- Andrew
It would be the manufacturer that cuts a deal with the distributor. Some of those pages in the DigiKey catalog look like advertisements.
There is no shortage of games that are played when selling chips. One place I worked was selling 1488 and 1489 for pennies. Granted as a designer, this wasn't my job, but I was curious how the price fell so fast. I figured it might be those darn 232 chips with the charge pump. But alas, some sales wizard set up a package deal to sell the interface chips with the modem chips. The interface chips were marked down since there was huge profit in the modem chips. As you can guess, the modems went to the next generation and the cheap price for the interface chips became the standard price for everyone.
Remember, in sales, you make your commission on the sale, not the profit.
It's not prototyping. That's easy. But manufacturing with reduced footprint and really high components density might lead to interesting components walking problems... I've seen some interesting, I think Philips, reports regarding this point indicating that there's a gap here between 0402 and 0201.
-- Thanks, Fred.
able
e t fon
tor
oTo avoid having sense the current at a node that slews in voltage, you can do one of three things.
You can measure the current on the load side of the working inductor. This requires that the "high side measurer" still work when the voltage is near ground. This is the way I went most often.
You can measure the current into the switch. This means that you cant measure when the catch diode is conducting. You may have to take special measures for the shorted load case because the on time can fall to the minimum and still be too much. To solve this, you can switch to a low frequency in that case as some Linear switchers do. You can also make it so that your switch is not allowed to turn back on while the catch diode is conducting. This ensures that operation is always discontinuous. At light loads, the frequency tends to rise. At some point a second off time limiting action needs to kick in. I have done this by allowing the "set point current" to take on a negative value.
The third idea is one I have never tried. They make chips that sense the current in a trace magnetically. They are basically a GMR sensor in a SO-8. You feed the current on a trace under the part.
Yeah, that's why the super cheap chips won't work here. It must be something that is able to do what a LM324 is able to do, measure all the way down to -300mV while supplied only a positive rail. I have a separate 5V rail for other purposes so that'll be the easy part. However, I'd like to know which of those chips have achieved "jelly-bean status". Naturally that excludes a company stating with "M" :-)
That's a bit iffy. Burp mode is no problem and I can get nearly any chip to do that even if that is not a native mode. But the sensing should be a bit more precise.
Hall sensing? Digikey seems to have only two parts. A Maxim for continuous read (but a vendor I won't use) and an Allegro for on/off, has two channels in there so a warning stage can be defined. However, it's single sourced.
-- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
Do you have a problem using rail-to-rail OpAmps?
What precisely are you trying to do?
A rail-to-rail OpAmp, a PNP and three resistors (counting the shunt) can give _very_ precise current measurement.
...Jim Thompson
-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at
Measuring current in a positive rail without failing to do so when the rail is shorted to ground.
Only if you feed the amp from the converter input side and in this case it'll be tough because of wide voltage range there. The output side cannot feed it because even the best RR amps quit working at 0V supply ;-)
I will have a logic rail but it's lower than the converter outputs so RR ain't enough there. Need "beyond positive rail" which common current sense chips offer for around $1-2 a pop. But I'd like to know which of those are truly "common", meaning there is a chance that they stick around for the next 10-20 years.
-- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
Current limit "regulation" or "snap off" ??
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
Stormy on the East Coast today... due to Bush\'s failed policies.
Ideally, regulation. I want them to be able to read actual current into an ADC and then issue warnings such as "Hey, you are at 80% and if you connect more stuff then ...". Two "snap points" might be ok, like one that I'd set at 80% for warning and the other to cut the loop at 100%.
Chips like these do the linear thing nicely:
However, while the price is ok (ain't that nice for a change ...) Digikey stock is lowish and I've seen clients get burned by former BB parts. That rocky phase at TI seems to be mostly over but you know how it is after allocations or uncertain leadtimes happened. It leaves that sour taste.
Someone suggested the AD8211 and the stock situation looks a lot more promising:
Since I am normally doing the opamp thing for series production gear I am not familiar with what kind of I-sense device has the highest chance of sticking around.
Needless to say, they are not pin-compatible. Of course not :-(
-- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
Those both take an auxiliary supply.
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
Stormy on the East Coast today... due to Bush\'s failed policies.
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.