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Is there a processor that works with a maximum current of 50
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MCUprogrammer



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Is there a processor that works with a maximum current of 50
PostPosted: Tue Mar 21, 2023 3:00 am     Reply with quote

It will have 8 bit DAC.
It will produce 3.1KHz frequency with PWM.
It will work with 5V supply.
I am looking for a processor with a minimum of 16 legs and a maximum of 28 legs. Do you know a processor?
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Ttelmah



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PostPosted: Tue Mar 21, 2023 4:49 am     Reply with quote

Every single PIC....

Completely dependant on how fast you run the processor. Run at 4MHz,
and I cannot think of any PIC processor that draws more than a couple of
mA.
Also depends massively on what else you are running. On your previous
questions about this over half the current was other things on the board.
PCM programmer



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PostPosted: Tue Mar 21, 2023 4:57 am     Reply with quote

Go to this Microchip page:
https://www.microchip.com/maps/microcontroller.aspx

1. At the top, in the CPU box, select the type of PIC that you want,
such as "8 bit PIC". De-select the other types, such as 32-bit, and Future.

Wait a few seconds each time you change something, because it takes
time for the page to automatically reload with the results.

2. In the CPU Type section, choose "8 Bit PIC MCU".

3. In the Packages / Pin Count section, set the left column for 16 and
the right column for 28.

4. Go down to the IC/OC/PWM section, and set PWM Chan = 1
in the left column. Don't touch the right-side column.

Look in "Search Results" to see the PICs available.
temtronic



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PostPosted: Tue Mar 21, 2023 5:05 am     Reply with quote

You don't specifically say it but It sounds like you want a battery to power the PIC and not 'Mains' ? is '50' 50 milliamps or 50 microamps ?
If this is true, then you need to look at 'low voltage' series of PICs and cut code that minimizes power. There are dozens of simple 'tricks' to minimize current comsumption.
If this is a battery operated project then you need to post design details like time it has to operate (week, 3 months, 4 years ?? ). Can it go to sleep ?
Microchip has an application Note ( AN608 ? ) about saving power, it's a must read.
As Mr. T points out , it's what's connected to the PIC that'll draw more current.
MCUprogrammer



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PostPosted: Tue Mar 21, 2023 5:16 am     Reply with quote

@Ttelmah Yes, you are right. I was using the LCD and LEDs to debug and suppress some values while designing the board. But as a result, LCDs and LEDs are no longer needed. What they want to do is just what I asked. Also I am reading inputs with 10us interrupt. If I try to do this with crystal with 4Mhz I will have problems with command execution. Or I can test it.
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MCUprogrammer



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PostPosted: Tue Mar 21, 2023 5:19 am     Reply with quote

@PCM programcısı The problem is that the page opens too late for me. It freezes. And I am not getting full results.
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MCUprogrammer



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PostPosted: Tue Mar 21, 2023 5:21 am     Reply with quote

@temtronic No, it will not work on batteries. It will work with the motherboard's power supply. I'm talking about 50 milliamps.
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temtronic



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PostPosted: Tue Mar 21, 2023 5:59 am     Reply with quote

OK, 50 milliamps is a HUGE amount of current ,so any PIC will easily work...
but..
it's all in the 'details',like we now know you have some ( 1,5,2 ?) inputs that have a 10us interrupt in addition to the PWM and DAC outputs.
since you have inputs, what pullup values have you chosen ? At 5 V you might be able to use 100k, 1M or even 10M,depending on the source of the signals
if this 'module', 'daughterboard' is active 24/7 , then 'sleep' mode isn't possible ? if timing is critical, you need xtal/caps but there might be a 'low xtal ' power configuration ?

kinda curious about the 50ma limit. seems 'silly' that anyone would design/use such a small power supply today as it'd cost nothing more to make/use one good for 100ma or even 250ma.
MCUprogrammer



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PostPosted: Tue Mar 21, 2023 6:29 am     Reply with quote

No, there is actually no such thing as a 50ma limit. It may be lower. I gave the supply voltages to an MCU I was wondering about. For example, let's take PIC18F26Q71. I made the MCLE connections. I used HFINOSC16MHZ. I'm assuming that I feed it with a 7805, which reduces 12volt to 5v as power in the circuit. How many mA does this processor draw at idle? So if I connect a serial DDM/Avometer to the MCU's supply line, what will I see? Does it draw very low ma? So initially it draws, for example, 20ma. Then it increases as LCD, LED, Button etc are connected. Yes, I'm okay with that. But when I connect DDM/avometer to the processor, I see a minimum of 85ma and a maximum of 120ma. I'm probably making a mistake somewhere.

But I see the following values in the Absolute Maximum Ratings section of the Electrical Specifications section of the datasheet.
Maximum current(1)
• ten VSS pins -40°C ≤ TA ≤ +85°C 350 mA
85°C < TA ≤ +125°C 120 mA

• on VDD pins (28-pin devices) -40°C ≤ TA ≤ +85°C 250 mA
85°C < TA ≤ +125°C 85 mA

• on VDD pins (40-pin devices) -40°C ≤ TA ≤ +85°C 350 mA
85°C < TA ≤ +125°C 120 mA

• on any standard I/O pin ±50 mA

Clamp current, IK (VPIN < 0 or VPIN > VDD) ±20 mA
Total power dissipation(2) 800 mW

So a maximum PIC can draw 350ma?
And also, you said there are tricks to reduce current consumption. Can you give a few examples?
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temtronic



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PostPosted: Tue Mar 21, 2023 7:13 am     Reply with quote

Think of the 'absolute maximum specs' are those someone measure just before the PIC destroyed itself. Like a speed limit sign on a highway that says 100Kmh. you can drive all day at 62, but go 110 and you die.

You need to look at 'typical operating' values. For that PIC, at 64MHz, 3v it's about 15ma so seeing 85-120ms is a HUGE problem. It it's true, then that PIC has to be warm to the touch,a finger will tell you.
You need to figure out WHY you're reading that high a current !


I'm curious and have to ask why so concerned about power, since you have more than 50ma available and it's not on batteries ?
Ttelmah



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PostPosted: Tue Mar 21, 2023 8:11 am     Reply with quote

and the point about the maximum power ratings there is they have to be taken
in conjunction with what the pins are rated to deliver. You can deliver a
maximum of 50mA out of each pin. Drive 8 pins and you'd draw 400mA.
The total max is saying 'yes each pin can deliver this, but you cannot
drive this on all the pins at once, without overheating the chip'.
On rated current, typically a PIC at 5v, will draw about 2.2* the same chip
at 3V. Just slightly less than a square law with voltage change. Pretty close
to linear with frequency change. So your chip is rated to draw 2.5mA at
3V, with the peripherals enabled. At 5V, just under 5.5mA. However load a
single pin with a 50mA load and suddenly the consumption is 55mA.
jeremiah



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PostPosted: Tue Mar 21, 2023 8:22 am     Reply with quote

MCUprogrammer wrote:
Yes, I'm okay with that. But when I connect DDM/avometer to the processor, I see a minimum of 85ma and a maximum of 120ma. I'm probably making a mistake somewhere.


This sounds like either an electrical design issue or an incorrect measurement setup. I'm running pic24's at 32MHz without going to sleep and I am sitting in the 20mA range (and part of that is my ICD programmer).

If current draw is really important to you, the first thing you need to do is make an "isolated" development board with just the PIC and the necessary parts for the PIC only (any power regulators, capacitors, crystals, etc). See what your current draw is. It should be low current draw. Then start adding stuff bit by bit and when the current draw increases you'll know what is causing the high current.

There's also software considerations, but you need to get the baseline electrical design correct first.
Ttelmah



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PostPosted: Tue Mar 21, 2023 8:33 am     Reply with quote

and of course on the particular PIC he mentions, you have the ability to
power off each peripheral separately. Only turn on the ones you are actually
using, and you can halve the consumption straight away.
MCUprogrammer



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PostPosted: Tue Mar 21, 2023 9:12 am     Reply with quote

@temtronic Thank you very much for the clear example Smile
There are extra components in the circuit. I am doing ISA BUS control. And the idle current is 500mA. The less power it uses, the better. Smile
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PostPosted: Tue Mar 21, 2023 9:15 am     Reply with quote

@Ttelmah and jeremiah I will do so. I'm going to turn off the peripheral I'm not using. And I will try step by step. Thanks for the answers.
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