5V buck converter
Today, I finished testing new lightweight boost converter. It is intended as a replacement for my ever-popular 3.3V to 5V converter. The new one is built around Texas Instruments’ TPS61240. It has slightly less output current (rated at 400ma) but is much simpler ( uses just 3 external components ), has several protections built-in, as well as undervoltage lockout (UVLO), which makes this power supply suitable for portable DIY devices.
Take a look at the title picture as well as the datasheet. Here is why I like this controller. First, it has been designed for battery-operated applications – thanks to built-in 2.1V undervoltage lockout it is safe to run this converter from 3 NiMH cells or one LiPo; when battery voltage drops down to UVLO threshold, the converter automatically shuts down. Second, the working frequency of the converter is 3.5MHz, which means that small and inexpensive MLCC inductor can be used. The converter also works well with ceramic capacitors. The total part count is 4 including the IC, and all components are cheap. Lastly, over-temperature and over-voltage protections make this simple supply quite robust.
tps61240 testing
The following picture shows the test setup. A pair of 10 Ohm 10W sand resistors make a 250ma load. Oscilloscope probe inserted into BNC connector directly soldered to the output and ground. Blue cylinder on the right is a magnetic probe used (after amplification, peak detecting and pulse forming) to trigger the oscilloscope from the inductor current pulse. While running with this load, converter IC and inductor are cooler than load resistors. When loaded to the maximum, converter gets quite warm but still runs stable.
The power supply can be used as ordinary 3.3V to 5V converter. It also has an ENABLE pin, which can be used to turn the IC on and off. By default, ENABLE pin is tied to VOUT. In order to use it, it is necessary to cut a trace inside a solder jumper.
I’m planning to start producing this converter and offer it for sale in about a month. In the meantime, I have about 10 blank PCBs left from prototyping run. If anyone is interested, drop me a line – the PCB is free, you’ll only pay shipping.
Oleg.
Sure, wouldn’t mind one of those pcbs if they are still around. Send me an email and we can set it up.
Uhm, that’s a boost converter, not a buck converter.
“boost”, as in “boosts the voltage”.
Thanks for catching this – fixed!
Very nice!! I’m definitely interested in on of the prototyping PCBs if you have one available. I’m looking forward to these being available for purchase, too. –Michael
Hi Oleg. I looked for an eagle footprint of the TPS61240. Could not find one: I guess you made one yourself?
Would you share it?
Sure -> http://www.circuitsathome.com/wp/wp-content/uploads/2011/01/CH_TI.zip . This is my TI library, with TPS61240 and some other parts, too.
Hi
I would like to use it to power both atmel MCU 3.3v and usb memory 5v
can it be done with one model?
do I need 2 models?
any other suggestion how it can be done? (regulator?)
thanks
You can’t get 2 voltages from one booster. If you need 2, generate one from another. For example, regulate to 5V and then drop 5V to 3.3V with LDO. It will depend on currents necessary for your 5V and 3.3V loads, sometimes it’s more beneficial to have 3.3V as a base and then boost it to 5V.
i would like to purchase the remainding PCB off you, i am currently trying to use power CY7C63723C-SXC controller (5V) from mini-pci-e. which is 3.3V
I have plenty – how much do you need?
I would like to buy an assembled version of this board. If that is not available, the bare PCB and any available parts you have in stock would be great. This board is more useful to me than the SparkFun LiPower because you have exposed an Enable pin.
The PCB is available here -> http://www.circuitsathome.com/products-page/power-supplies/ I don’t have anything else left, sorry.
That looks like the board for the LTC3426 chip. For my app, I need shutdown to disconnect the output load, which is not done by the LTC3426 chip but is done by the TPS61240 chip. Do you have any boards for the TPS61240?
I looked around and can’t find any PCBs left. This is the link to BatchPCB, you can order it here -> link
[…] is disconnected from the input battery, making the MOSFET in the above circuit unnecessary. A converter board has been designed by Circuits@Home, and I currently have some on order. Because the MOSFET is not […]
Are you producing this converter anymore? I would like to purchase two of them if so.
Thanks,
Daryl
I’m afraid I’m not ready to sell them yet. Have you looked at this -> http://www.sparkfun.com/products/10255 ?
I ordered some bare boards from BatchPCB, as Oleg suggested. They sent me more than I ordered; I can mail you two if you send me your address (no charge), tabb99 at gmail.com. Building them was my intro to SMD soldering. I think the Hot Air Rework station” from SparkFun was the key to soldering the converter chip.
This is what always happens when you order small boards from BatchPCB – they make a panel from several orders starting from big boards and then fill all unused space with small ones.
[…] part of my Arduino Power Controller project, I ordered and received the PCBs for the Circuits@Home boost converter utilizing the Texas Instruments’ TPS61240 chip. My SMD soldering experience is close to […]
This is a great find. It took me several weeks of on and off browsing…
When will the assembled part be available?
I’d love to get my hands on a few of these boards but the BatchPCB link no longer works due to their move to OSH Park. Does anyone have any for sale or the gerbers or other design files?
Hi Oleg, are you selling this? Interested to get a couple of them, but I can’t seem to find them in the store.
Thanks!
No, I’m not, sorry.
Great article!
Hand soldering that SON package should be fun!
Did you place thermal vias through the thermal pad on the PCB?
I am laying a board out and I am wondering if they were necessary.
Thanks!
In my experience, vias through the central pad make soldering easier so I always place them.
Is the assembled part available now ?
this one has never made it to production
Thanks Oleg.
Can you advise any alternative?
Check pololu.com .