Stumbled on this interesting part from TI recently
TPL5111 solves a typical problem in low power wireless systems- things need to be off most of the time, and wake up periodically to transmit. The usual solution is to pick a microcontroller that can stay asleep in low power mode at a few uA, then wake up on RTC timer. That works most of the time, but sometimes even that is too much standby power. Imagine a system for example that has to work from a small coin cell for 5-10 years. Each uA of sleep current is an 8mAh a year. So in 10 years, 80mAh is wasted. (A typical CR2032 battery for example starts with only 220mAh)
TI’s solution is a timer that can stay on while drawing 35nA. Once set with a single resistor for a particular time interval, between 100ms and 2 hours, it turns power on to the system, waits to hear back from the micro via “done” pin and then turns things back off. TI even provides a handy table of resistor values vs timer settings. Not bad for $0.45@1k, plus there are many other scenarios such an almost zero power scheduler may be handy.
This week’s part of the week is a Linear Technology’s LT8584. The part is a DC-DC converter that is designed for a very specific purpose- active balancing of battery cells. In a typical long battery string, no matter how tightly matched initially, there will always be cells that end up with a bit more or a bit less charge. Over time these imbalances start affecting what the battery can deliver, as one week cell may trigger undervoltage limit for example and shut the whole pack down despite other cells being perfectly happy. Continue reading
After a long hiatus, part of the week section is back. This week’s part is actually a bit more than just a part. It’s a whole concept called Tag Connect. When I first saw their ad, I smacked myself and said “why didn’t I think of that?!”. I am sure many others did the same, as it just takes all the things we’ve already been doing and makes them even better. Continue reading
This week’s part is a neat little chip from Texas Instruments. TPS2511 USB Dedicated Charging Port Controller and Current Limiting Power Switch. What this chip is designed to do is handle a bunch of newly developed USB charger handshaking protocols. As many familiar with Adafruit’s Mintyboost and other similar USB chargers for portable devices are aware by now, is that not all devices will charge if you simply give them 5V on a USB connector. Many will expect a particular level on the data lines, like certain i-devices, as documented by LadyAda. And yet others will want data lines to be shorted together to recognize the charger. This chip was designed to handle that automatically and hopefully provide a way to support future devices. Another nice feature is cable drop compensation. With high charging currents, the drop across that 6ft USB cable is no longer negligible. So what this chip does is add a bit of bias current to the feedback pin of a power supply feeding it. By doing that it is raising the output voltage by a predetermined amount to compensate for the drop. This feature activates when a load current exceeds a preset threshold.
TPS2511 typical connection diagram
Very nifty chip- expect a writeup for a project using it soon. But first we must get the boards back from the fab and see if anything smokes!
A neat little sample kit has arrived: it’s a Linear Tech TimerBlox set.
What have we got here?
This week’s find is a NSI450xx/NSI500xx family of parts from On Semiconductor. It’s a two terminal constant current regulator (CCR) offered in SOD-123,SOT-223 , SMB, SMC and all the way to DPAK cases. The device can handle 45V surges and regulates current to 15-350 mA depending on the individual part number. This makes it very convenient to insert into LED strings and have them stay in regulation and constant brightness with variable input voltage. Continue reading
Another new section starting today- part of the week. There are many other “chip of the week” out there, so here I’ll just mention things that I personally find interesting . They may be chips, or other electronics parts. Today’s find is an Atmel AT24MAC402/AT24MAC602 – an I2C 2K EEPROM with a stored and read-only 48 or 64 bit EUI address and a unique 128 bit serial number. The parts are very cheap (25 cents) and serve a very useful role. Say your company is making a product that uses Ethernet. Typically an EEPROM on board is programmed with the MAC (EUI-48) address during board test. By simply switching to these chips, a step in manufacturing is omitted, saving time and money. Atmel also thought about companies who would like the MAC address be from their own pool of numbers- they would custom preprogram them as a special order. Overall, a pretty simple idea that will save customers time and money!