Wish list: Power/battery management IC

I mentioned I am playing with battery management. It is clear some interesting ICs out there. One of the problems is that there are so many ICs with so many variations, even if one just looks at one manufacturer like TI (who do some cool ICs).

So I thought I would try and explain what would be an ideal IC for some of my projects. From what I can tell this is all available in various ways with various ICs but not as one simple IC. I am not actually asking for much, honest. I have some of this pretty closely now but in a lot more components than is ideal.

There are some monster large QFN power management ICs out there as well, which seem overkill, and not sure I have yet found one with the "button" aspect.

So here is the list of what I would really like.

1. A small IC, probably not actually BGA, but small, a QFN package or even small SOP style if few enough pins. It does not need a lot of pins for what I am talking about. TI have some funky QFN style packages with larger pads for the power, that would be fine. Ideally not special handling at PCB manufacturer (hence not BGA).
2. A 3.37V LiPo connection for one LiPo cell.
3. A 5V power input connection, i.e. from USB.
4. A regulated 3.3V output - ideally 1A but at least 500mA. Can be switched off.
5. A simple push button input (see below). Maybe also button state output pin.
6. An I2C interface (see below).
7. Perhaps even a "reset" output, that rises once power has stabilised, drops before power off - this saves a couple more passives.
8. Perhaps even a LED output (I don't really need this).

Now the idea is simple, this provides both regulation for 3.3V working of a device, running from 5V and/or 3.7V LiPo, but also provides battery charging for the LiPo from 5V. There may need to be a pin to define charge rate, and even a pin for voltage output, but a fixed 3.3V saves more passives.

The regulated output could be a simple LDO type thing, or perhaps a synchronous step-down with integral FETs and small external passives. Minimal passives is ideal. Needs to run off 5V or 3.7V, i.e. work when there is no LiPo.

The idea of the button is simple. The device would have off or on modes. When off, and just on LiPo, its current needs to be a few uA at most, and no 3.3V output. But the button is used to turn on. The button could also have a last ditch "hold for 10 seconds" power off to allow it to be used as a system reset. It makes sense to turn "on" when powered up, and when 5V applied, as processor can decide to turn off if not needed.

I2C would allow checking state of battery, and 5V. Ideally an ADC for battery voltage, maybe even for 5V supply voltage too. Needs a way to check button state so it can be used when on for other functions, or perhaps a pin output to mirror the button. Needs a way to tell the device to go to "off" mode. A pin output mirroring button is probably best as this allows for processor (e.g. ESP32) in low power sleep when this chip is "on" and still use button to "wake up". There could be some special power regulation modes for extra low power but still "on" perhaps to allow this type of working as well as a proper "off".

I can't help feeling this fits the needs of a wide range of small battery operated devices.

If anyone knows of devices that tick some of these boxes, please do let me know.

Oh, and reverse polarity protection and reporting, thermal shutdown, etc.

Some feedback I have had, thank you all.

• https://www.ti.com/product/BQ25155

Faikin board ATE

The Faikin boards are a development board, a component to fit in to your Daikin air-con as your own project.

However, I do try and make sure they work before shipping, which means some testing. This means flashing some code and doing some tests.

Basically, there is always a small risk of badly placed, badly soldered, or faulty components on any board. It is rare, often less than 1 in 500 boards. But it is a risk.

TC2030-USB

The key component is a TC2030 lead - it means a simple pattern of pads and holes on the PCB (which essentially has no cost), and a suitable lead (which costs a bit more).

Oddly TC2030 seems to be one of the very few sprung pin header leads you can get for this. I would have expected way more, but they do seem pretty common and standard, and they just work.

The lead allows me to power the board and connect to USB to flash the processor module (ESP32-S3-MINI-1-N4R2). The programming batch process is pretty slick. I end up doing several in parallel and putting in anti-static bags, all pretty slick now. Yes, manual labour which I am not used to, but I am getting good at it. Amazingly the process of then labelling the bags takes pretty much the same amount of time.

The flashed code then operates the LED on board so I know it is all flashed and working. Simple. Basically, to get as far as an LED means partition table, boot loader, and code, all working (all signed and checked) to get as far as the sequence for a WS2812 LED. So this is not just some GPIO happens to be low, this is proof of code running cleanly - a good test.

But this only tests the USB, power, reset, and ESP32-S3 module and flash and RAM. Not all of the other electronics for Tx and Rx with the Daikin. These extra bits have some components because they have to level shift to 5V open drain logic with pull ups as used by Daikin.

TC2030-USB+

Can I test these remaining components? Well yes, I can...

The trick is to take the final pins that go to the Daikin for Tx and Rx, and feed them on to two spare pins on the TC2030 spare pads.

Then I make a custom lead that has USB but shorts those two pads.

This means my code can do a loop back test on the final Tx/Rx from the Faikin board, and indicate red not green on the LED if it is not seeing a loop back.

This tests almost all of then components (there are a couple of ESD diodes which it doesn't test other than that they are not a short - but that works as a visual inspection mostly).

Always valuable lessons learned as I go.

Battery life

I am doing well learning my way with battery based circuits. But it has taken some time to get the hang of it.

ESP32 deep sleep

The first thing is the ESP32 can go deep sleep, with controls of some GPIOs that can have set states and be used to wake from sleep, or a timer. Using this with a simple LDO regulator from a 3.7V LiPo I know I can make a device that lasts for several weeks on a charge from a pretty small battery because the Watchy does this. The nice thing is this is deep sleep most of the time, with timed wake to update display every minute. It works, and I have made similar circuits myself.

Leaks

However, some of my designs are not as long lasting, maybe a few days of idle/off time. The reason is that the idle current needs to be very very low, a few uA. Deep sleep on the ESP32 is that low, which is ideal.

Well, except you can set GPIOs in some states and that could use current. If careful though, e.g. week pull on a GPIO input to a button which is not normally pressed, you can indeed keep the current that low.

But there is one annoyance that has led to standby times of more like a day, and that is the nice WS2812 style status LED I use. Its idle current when off is still typical 350uA, which, by comparison to the CPU is huge! There can then be other devices that use power, and even the LDO will leak some.

The solution was a simple pair of FETs to switch the LED off, though for a single status LED I could probably power directly from a GPIO, which may be a neater solution.

This has led to many days standby - well probably indeed the few weeks as I measured on the Watchy.

More LEDs

Once example where this was a lot more of a problem, leading to standby times of more like a few hours at most, was the IronMan glove with 88 LEDs, so idle was more like 30mA. That was a mistake, and one reason I wanted to improve things a lot.

Point of load / power distribution ICs

Whilst a simple pair of FETs works well for controlling power to LEDs, there are some devices really intended for this, which are very cheap, and really quite clever. An example is the TI TPS22916. It is tiny (0.78mm x 0.78mm), has power in and out, GND, and a control input, and that is it.

Its job is to switch power input to output, simple as that, but it has a slew rate to reduce input current surges, and the control input is a simple logic level, active high, that will switch from as little as 1V, so will work directly from a GPIO, no other external components at all. It also has thermal cut out.

This makes it much smaller and neater than a dual FET, plus two resistors, and better and safer (the slew rate and thermal cut out). It also has a standby of typical 0.1uA, so basically nothing.

This makes it ideal to control the LEDs, even when only one status LED.

But there is more

I think I can do better. The idle ESP32 has some current and the LDO will have some even when idle. What if I could eliminate almost all power usage when off.

This is my plan...

I'll explain...

This idea is the LiPo (the connector at the top) feeds in to two of these switch ICs. It could be just one if all I wanted was an on button. This idea is the button links the battery to the switch IC control - the switch IC even has a built in pull down so no extra component needed. When button is pressed power comes on.

Then a GPIO (PWR) is driven from the processor - if I only had one switch IC it would be linked to the button to logically hold it pressed. This keeps the power on until the processor commits suicide by lowering that GPIO level.

By using two switch ICs I can still keep things on from a GPIO, but by linking the button to a GPIO input, I can still detect the button pressed when on. Button press does nothing for power when power is already on, but the CPU can tell the button is pressed, and use that, including using it as a power off switch if wanted.

The concept is that when logically off (and this means no wake up on timer, properly off), the only leaking current is of the order of 0.1uA (x2) through the switch ICs. Not even leakage via the LDO or the deep sleep processor applies. This should allow the battery to last a long time, e.g. even a tiny 150mAh should last decades in idle, with the batteries own internal leakage being more of an issue.

So, ordering some sample boards to test.

Update:

The new boards have arrived, and the good news is that the power on/off works as expected. It was a tad fiddly making power down work, needed held GPIO in open drain mode, but it worked.

The only snag is that the button does not work on USB only with no battery. It connects the input to the battery, and there is no battery. My hope was the charger circuit would be providing some voltage on the battery pins that would allow the button to work, and indeed, at one point it seemed to, but no, this is not the case. So I need a new way for the button to work. The main idea is a two poll button, which means one side to a GPIO for button working logic, and the other to the power control for power on. The good news is that can make it work using just one power controller and not two. Now to hunt for a nice two poll button!

Tax, duty, VAT, GST, Tariffs on import?

I sell stuff on Tindie. (see www.tindie.uk).

Now, when you get it, if not in UK, your courier may charge you some amount of tax, duty, VAT, GST, tariff, or admin fee on receipt. Pain in the arse, I know.

So could we sort this as seller?

Well, basically, we have no way to know what tax, duty, VAT, GST, tariffs, or admin fees might apply. It is not even a simple per-country thing - it depends what you are selling, and the country, and in some cases even matters what region in the country where you are located. If you are registered for VAT/GST in your country you may be able to avoid some charges on import. It is simply impossible for us to work this out, even if we wanted to.

And, of course, in some countries (sorry USA), the tariff may change from day to day at the whim of a mad man, so really we would have no clue. 

Even if we knew?

Even if we knew the exact amount you are liable to pay, I have no easy way to "pre-pay" that as sender. Some couriers clearly do this (my experience being EU based VAT, and even some US shippers to UK, surprisingly), but Royal Mail, which we use, do not seem to have any way - we just have a customs form to complete on sending, and you end up paying the extras on receipt - we have not way to pre-pay your import costs.

Even if we could pre-pay?

But even if we could work out what is due, and even if we have a way to pre-pay it for you, what then?

Well simple, it adds to the cost for us, so we would simply add to the price. Indeed, that could mean more, as setting our price higher to cover such charges probably impacts the charges as they are often a percentage of sale price. So actually, if we could work out what was due, and pre-pay it, it may mean we end up charging you even more that if you just paid it on import.

So, tough.

Simple answer is we quote a price, we charge a price, and you get to pay your government any import duty, tax, VAT, GST, tariffs or whatever when it arrives. Sorry.

Canon CT-21

So, I like it. But there is some learning...

Colour

One aspect is setting colour options, and ensuring it knows the paper type, else you get too dark or too blue, or whatever. This is a general thing anyway with colour printing, but on my PRO-1000 I only printed on the same proper photo paper all the time, and so it always just worked. On the CT-21 I have a roll of A1+ "coated" paper. It needs slightly different settings.

Paper Size

This is where it gets fun...

The paper is A1+ width, i.e. 610mm (A1 is 594mm). Fair enough, it means you can print over size, and cut down with bleed over the edge of the print. The catch is you need a big cutter or are good are cutting against a straight edge.

Just to be clear, A1+ is not the max size, it will print up to 18m long from a roll - a banner, which is just crazy!

The print driver essentially allows basic size options, for example, for A1, it can be A1 with 5mm margins, A1 borderless, or A1 oversize borderless. The A1 is great if you are putting in a frame with more than 5mm edges. A1 borderless is great if the frame has little or no border, or if cutting to A1 exactly. Oversize A1 is great for that bleed over the edge, but still has margins of a few mm on the A1+ paper each side and at the ends of the print.

Then there is a "scale to borderless roll" which goes to around 609mm wide, a slight white edge each side. It also cuts the length in to the edge of the print by a few mm. This means you get an over size print with two cut edges and two very narrow white edges.

Confused? Well, yes, too many options.

What I did was make the oversize with print close as you can, and ended up with nice over size A1. The snag is they don't fit in the clip frames so needed cutting, on all four sides.

Now, it can, of course, do A2 on the same roll, sideways - well A2+ (all the same issues, just on the other two edges).

But A3 and smaller I can use the sheet feeder and plain or photo paper, etc. However it does not do borderless at all on the sheet feed, always at least 5mm borders, so a tad more limiting.

Three sided borderless

There is yet another option - 3 sided borderless, and I realise now that this is actually what I need to use.

It prints the image the size you selected, so typically A1 exactly (to then go in a frame, but no scaling or cropping involved from the original artwork). But prints it as far to one edge as it can, and then cuts the start and end. This means you have two cut edges, one very close to edge, and one margin. The margin means only having to cut (or fold over) that one side of four. This makes it very easy to put in a clip frame, or only one cut to use with no frame.

This also means I could print smaller sizes, A3, A4, etc. These are extra easy as the (now quite large) margin fits in my guillotine. It also means all the same (roll) paper with the same colour settings, and edge to edge, unlike using the sheet feeder.

This is an example of A1 three sided borderless - only one side needs cutting or folding over. This is 840mm left to right.

Some more of my videos

I have done a couple of videos on my circuit boards.

The fun one, I hope, is the "shopping channel" style one.

But also a more instructive one on making circuit boards.

And one on the Faikin boards specifically.

Canon PRO-1000 vs CT-21

I have had a Canon PRO-1000 for some time, it is an amazing printer. It is a must for someone producing professional photographic image prints. I cannot stress how good quality it is.

But I have just replaced with a Canon CT-21. So I felt it's worth explaining why, and what difference it makes.

Do I need a photo printer?

The first point is whether I need a photo printer. It is my only colour printer, and I do print photos for the family that get framed and go on walls, and so on. But I print stuff like a menu with a colour logo on it, etc, which seems overkill to use a PRO-1000.

Basically, I probably do not need a professional photo printer, really. It is just my usual overkill.

What is my use now?

Given the ability to print up to A2, I have actually been using it for posters for the pub. They are stunning.

Is A2 big enough?

The catch is, posters at a pub, may want more, like A1. So I decided to get the TC-21, which is an A1 poster printer that takes roll paper feed. If someone accidentally orders A0 clip frames at the pub, I may be in trouble.

What of TM-255?

I considered the TM-255 - it uses 5 inks, not 4, but has a base, and is just so big. It looks great, but I simply did not have space. The TC-21 fits on my bench. The ™-255 is also high volume and stupidly quick, but the TC-21 is not a problem for what I need in terms of print speed.

Key points in favour of the PRO-1000

• The photo print quality is just amazing, cannot be faulted.
• It does edge to edge printing on most paper sizes (oddly not A5), which is very cool. Even A2.

Key points in favour of TC-21

• It does A1+. Indeed, it will do 610mm wide and 18m long if you want!!!
• It does roll paper feed (which I am using for A1+ or A2+), but it can take narrower paper roll.
• It does sheet feed (no need to take out rolls feed, just manual sheet feed via top loader), all the way down to A6. Very handy.
• Easy colour refill - the PRO-1000 is easy, but this is only 4 inks.

Some downsides for PRO-1000

• It uses 12 inks, this is a feature in terms of quality but a pain in terms of costs and hassle with ink. It also gets through "maintenance kits" which also cost.
• If you do not use for a while, weeks, it will waste a lot of ink and take ages to start up. But it will then print perfectly. I don't know if the TC-21 does this.

Some downsides of the TC-21

• It is bigger, check dimensions, but wider by quite a bit. Well, obviously it has to be.
• It does not do edge to edge well - it can get very close on roll feed, maybe 1mm each side, and cut with no margin top/bottom. But not at all on sheet feed. This is perhaps its main lack of feature.
• It is only CMYK not 12 inks, but the photo printing is still good, and good enough by far for some family photos.

I do not know running costs yet, but the results are pretty good.