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AnsweredHot!Which PIC18 for LCD, RTCC, low power

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szlovak
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2020/12/03 16:53:01 (permalink)
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Which PIC18 for LCD, RTCC, low power

Hi
 
I find parametric search on Microchip or Microchip Direct a bad joke, really. I need :
-MCU that has less or around of 500nA in full sleep mode at power supply in range of 2.0-3.6V, that holds RAM content, not that deep sleep marketing bla, bla that is almost useless
-using  a 32768Hz quartz with only few uA like 3-5 of current after wake up, also in temperature that can get up to 85 C, maybe around 60 C will be enough
-drive a LCD with 4 common, 64 segments
-64kB program memory
-eeprom would be nice but not necessarily
-RTCC would be even nicer, but it is not the main concern
 
I thought about PIC24FJ256GB412 witch is the lowest from some XLP brochure, but it turned out a marketing **. Really I don't know where they found that 170nA of current consumption in RTCC and 70nA in sleep. Probably it all refers to deep sleep. None of power modes has that consumption and what even worse, with higher temperature it goes to 15uA on 32k resonator!!
 
Device that we want to make from scratch originally had MSP430 from Ti, and what I can see it could drive LCD and has a nice current consumption over temperature ranges, but finding anything from microchip is a tough task. If anyone , anything , I would appreciate.
 
 
 
 
 
post edited by szlovak - 2020/12/03 16:56:37
#1
katela
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Re: Which PIC18 for LCD, RTCC, low power 2020/12/03 17:05:14 (permalink) ☼ Best Answerby szlovak 2020/12/04 04:45:59
+2 (2)
Did you use MAPS?

Free online Microcontroller Tutorials and Projects for Hobbyists and students. From beginners to advanced. Website: www.studentcompanion.co.za
YouTube Tutorials: https://www.youtube.com/StudentCompanionSA
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Kabak
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Re: Which PIC18 for LCD, RTCC, low power 2020/12/04 00:31:46 (permalink)
+1 (1)
PIC18F26K22
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NKurzman
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Re: Which PIC18 for LCD, RTCC, low power 2020/12/04 00:39:03 (permalink)
+2 (2)
Remember to get very low current your board must be very clean. The pins can’t be driving anything. And all internal profiles need to be turned off. There’s a list of what each item draws, like the internal oscillator and brown out reset. The real time clock Will most likely require you to wake up To periodically to service the time ( like once a second). It’s not a standalone real time clock chip built into the PIC.
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szlovak
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Re: Which PIC18 for LCD, RTCC, low power 2020/12/04 00:59:22 (permalink)
+1 (1)
thank you so much!! How it has happened that I've never seen this?
#5
Mysil
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Re: Which PIC18 for LCD, RTCC, low power 2020/12/04 04:26:51 (permalink) ☄ Helpfulby szlovak 2020/12/04 15:03:19
+3 (3)
 
There is PIC16F19xx   family of microcontrollers, which have builtin drive for segmented LCD display,
without need for external LCD display controller.
 
PIC16F191xx  family of devices, with PIC16F19156 with ability to control 96 LCD segments from a 28 pin package.
 
PIC18FxxK90 family of devices, also with drivers for segmented LCD display directly.
 
    Mysil
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szlovak
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Re: Which PIC18 for LCD, RTCC, low power 2020/12/04 04:46:36 (permalink)
+1 (1)
Kabak
PIC18F26K22


nope, it doesn't have lcd driver at all
#7
Howard Long
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Re: Which PIC18 for LCD, RTCC, low power 2020/12/04 08:15:20 (permalink)
+1 (1)
Mysil
 
There is PIC16F19xx   family of microcontrollers, which have builtin drive for segmented LCD display,
without need for external LCD display controller.
 
PIC16F191xx  family of devices, with PIC16F19156 with ability to control 96 LCD segments from a 28 pin package.
 
PIC18FxxK90 family of devices, also with drivers for segmented LCD display directly.
 
    Mysil




FWIW I've found that the PIC16LF191xx had quite a bit higher current draw than the older 16LF19xx series when driving static displays, that may or may not be a concern, but I was targetting a 1uA drain, that's pretty extreme for an MCU LCD application.
 
If it's a mux'd display that has greater current draw anyway, then I'd agree, the 16F191xx is a better choice.
#8
Howard Long
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Re: Which PIC18 for LCD, RTCC, low power 2020/12/04 08:32:22 (permalink) ☄ Helpfulby szlovak 2020/12/04 15:22:35
+2 (2)
OP: you don't say if the MCU needs to have the LCD operating when drawing 500nA?
 
The wake power up current is a tough one. Various bias circuits etc kick in during power up and it's often not pretty.*** see below
 
When I've compared PIC18F devices against PIC24FJ devices, practically speaking I've found that the PIC24FJxxxGA4xx outperforms the PIC18FxxK90 series in current consumption during LCD and sleep operation.
 
I did an example project, 1.8uA with both the the RTCC and LCD on using the PIC24FJ256GA410. I did not check beyond room temperature though. As a matter of interest, what is the use case for extended temperature? 
 
See my Youtube ref yyoR0o5YBVI for this project, and the eevblog link to forum post in the video's shownotes (sorry setting hyperlink is getting unauthorized error)
 
*** Edit: this is the case for power up, not wake from sleep: usually wake up current is similar to run current, however it can take a while for oscillators to stabilise, so this wake time often needs to be taken into account for power budgets depending on duty cycle, wake time and wake up time.
 
 
post edited by Howard Long - 2020/12/04 08:52:57
#9
Howard Long
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Re: Which PIC18 for LCD, RTCC, low power 2020/12/04 08:40:18 (permalink)
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Also from my post #38 here https://www.eevblog.com/forum/blog/eevblog-1242-memory-lcdsupercapslow-power-design/msg2669508/#msg2669508
 
Yesterday I did some evaluation testing with a few devices, notably PIC16LF1904, PIC16LF1934 and PIC16LF19175 that are largely pin for pin compatible drop in devices. 1ku pricing is $1.18, $1.46 and $1.19 respectively. All are available in 40 pin 5x5mm UQFN, but I used the DIP variants for this.

The best I managed so far at 3V with the display operating but with the CPU in sleep is on a PIC16LF1904, at 410nA plus 14nA per on-segment with the display attached, in static mode. This was using the internal LF oscillator, but no RTC functionality (I don't believe an RTC is a requirement in this case).

Measurements are taken with a Keithley 238 SMU and triaxial cable assemblies to the DUT. The MCUs were on solderless breadboard, and the debugger and any other probing removed. The LCD is DE 117-RS-20/7.5 soldered on a breakout board that had been cleaned in an ultrasonic cleaner.

As usual, you should never trust the datasheet when it comes to low power current draw specs: sometimes it's better, sometimes it's worse, and often the difference is dramatic. Judging by the quality of the quoted figures, I strongly suspect they use unsupervised interns on this work. Measuring sub-uA takes care and attention.

I found some interesting facets regarding the sleep currents. Sleep currents are important because they can be a show stopper before you've turned on a single LCD segment.

The typical sleep current for the PIC16LF1904 is listed as 160nA @ 3V, I was measuring only 17nA. The same applied to the PIC16LF1934 where the datasheet quotes 80nA @ 3V, and I achieved 16nA right off the bat. It's times like this you question your own measurement skills. Replacing the PIC with a 10Mohm resistor gave expected results, allaying any fears of a gross operator error.

On the other side of the coin, the PIC16LF19175 (a recommended replacement for the PIC16LF1934) measured 275nA at 1.8V, but at 3V it was a very different story, with in excess of 3uA (spec says 350nA). It's not clear to me why this is, but after spending half an hour tweaking I put it to one side, and concentrated on the PIC16LF1904, and getting the LCD operating.


 
#10
Howard Long
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Re: Which PIC18 for LCD, RTCC, low power 2020/12/04 08:41:51 (permalink)
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szlovak
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Re: Which PIC18 for LCD, RTCC, low power 2020/12/04 15:01:41 (permalink)
+1 (1)
Howard Long
 As a matter of interest, what is the use case for extended temperature? 
 




Thank you for much information!! It will be an application that is very near to hot water. I have to take it into consideration. 85 is most likely not going to happen, probably, but something above 60 most definitely will. I think, that what I have left, is to try it out all myself or choose maybe other brand of MCU. I will have 6uA average available current draw, but you never know under what conditions device will work. Some goes here and there and you are out of battery juice. LCD might be refreshed very slowly for my application, it will be totally fine to do so, but it has 4 coms. We would have to rewrite design maybe and use other LCD. So stability over temperature is the key problem, and that 15uA is very bad for that pic24 (and god knows how much in idle) , especially that they say it openly in manual, so I'll  probably will use PIC18F87K90, PIC18F97J94 or similar because of bigger memory available. That cryptographic engine was interesting...
post edited by szlovak - 2020/12/04 16:11:35
#12
Howard Long
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Re: Which PIC18 for LCD, RTCC, low power 2020/12/05 03:18:45 (permalink)
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If you're muxing, IME whatever solution you choose you'll be lucky to achieve ITRO 5uA per intermediate level common because biasing is expensive in current terms.
 
What is the 15uA are you referring to on the PIC24?
#13
Howard Long
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Re: Which PIC18 for LCD, RTCC, low power 2020/12/05 04:23:08 (permalink)
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By the way, regarding the PIC24FJ256GB412, I've found some notes I wrote some time ago regarding the need to turn off the USB transceiver for minimum sleep current, even if you never initialised it.
 

U1PWRCbits.USLPGRD=0;
U1PWRCbits.USUSPND=1;
U1PWRCbits.USBPWR=0;

// Enable the low power regulator during sleep (seems to save about 5uA)
RCONbits.RETEN=1;

// Disable all peripherals we can
PMD1=0xFFFF;
PMD2=0xFFFF;
PMD3=0xFFFF;
PMD4=0xFFFF;
PMD5=0xFFFF;
PMD6=0xFFFF;
PMD7=0xFFFF;
PMD8=0xFFFF;
Sleep();

#14
szlovak
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Re: Which PIC18 for LCD, RTCC, low power 2020/12/05 12:47:30 (permalink)
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Howard Long
If you're muxing, IME whatever solution you choose you'll be lucky to achieve ITRO 5uA per intermediate level common because biasing is expensive in current terms.
 
What is the 15uA are you referring to on the PIC24?


page 503, parameter "DC61" low voltage sleep. I think it's the most low power mode there is with RAM retention


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NKurzman
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Re: Which PIC18 for LCD, RTCC, low power 2020/12/05 14:30:37 (permalink)
+1 (1)
Keep in mind those currents are for the core only, not the entire chip. To get those car ones you need to disable every peripheral, and not be syncing or sourcing anything on the pins.
#16
ric
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Re: Which PIC18 for LCD, RTCC, low power 2020/12/05 14:33:09 (permalink)
+1 (1)
syncing -> sinking :)
 

I also post at: PicForum
Links to useful PIC information: http://picforum.ric323.co...opic.php?f=59&t=15
NEW USERS: Posting images, links and code - workaround for restrictions.
To get a useful answer, always state which PIC you are using!
#17
Howard Long
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Re: Which PIC18 for LCD, RTCC, low power 2020/12/06 08:36:20 (permalink)
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szlovak
Howard Long
If you're muxing, IME whatever solution you choose you'll be lucky to achieve ITRO 5uA per intermediate level common because biasing is expensive in current terms.
 
What is the 15uA are you referring to on the PIC24?


page 503, parameter "DC61" low voltage sleep. I think it's the most low power mode there is with RAM retention






FWIW, here were the room temp figures I collected for a PIC24FJ256GA410 under various conditions, and I achieved similar on the GB versions, which roughly coincide with the datasheet. There is some weirdness when going into deep sleep with these devices, as the Vcap drops below 1.2V, for a few seconds the current drain actually increases while, I assume, biasing of some transistors puts them into a linear region. It does settle at about 70nA though.
 
Neither the sleep nor the run currents, when taken in isolation, are great on this device. However, when viewed as a whole system, if you need stuff like RTCC and LCD with low duty cycle on the core, it can be useful.
 
FWIW, I found some notes on the PIC16LF1906 1/4 mux 1/3 bias LCD tests that I made. I had it running in sleep with the LCD, T1OSC xtal mode and TMR1 peripherals operating at 1.679uA @ 3.0V in 1/4 mux mode @16Hz frame time using the low power internal resistive dividers. When physically connected to an LCD, each OFF segment added 22nA and each ON segment added 40nA with a DE188-RU-30/7.5 8 digit 5mm height display. When out of sleep, I found that the most efficient processor speed using the INTOSC was at 16MHz, 919uA @3.0V. Sleep current with no peripherals was 15nA @3.0V, and 729nA @3.0V running TMR1 on T1OSC xtal mode.
 
 

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Antipodean
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Re: Which PIC18 for LCD, RTCC, low power 2020/12/06 13:36:50 (permalink)
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szlovak
-using  a 32768Hz quartz with only few uA like 3-5 of current after wake up, also in temperature that can get up to 85 C, maybe around 60 C will be enough
-drive a LCD with 4 common, 64 segments

 
Been following Howard Longs investigations and intrigued with the figures he is producing. But if you need to run at temperature then the current consumption IS going to go up - it is a fact of semiconductor physics.
 
Also does your intended LCD operate at the desired temperature? They do have a limited upper temperature limit.
 

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#19
Howard Long
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Re: Which PIC18 for LCD, RTCC, low power 2020/12/06 16:42:45 (permalink)
+2 (2)
I just ran my PIC16LF1906 1:4 MUX 1/3 bias 8 digit LCD project with sleep active LCD & TMR1+T1OSC, and 4s wake up on a ~10^-6 duty cycle @16MHz. all at 3.0V.
 
25C: 1.99uA
60C: 2.25uA
85C: 2.59uA.
 
YMMV, but I'd try it out, it's nowhere near as bad as the datasheet suggests.
 
I heated up the device with a hot air iron on the top of the package and measured the temperature with a thermocouple pushed underneath the package.
 
 

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#20
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