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Output voltage
08-03-2012, 03:15 PM,
#1
Output voltage
Is the output voltage of the Pinguino PIC32 OTG limited to 3.3V?
Or is there a way to get 5V out?
Can't find any information about the output voltages on the web.
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08-03-2012, 07:07 PM,
#2
RE: Output voltage
Unless you add a suitable device you'll get at most what the chip can do - which is in the data sheet. It won't be as much as 3.3V (because there's always a drop from the chip's supply voltage, due to internal silicon).

John
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08-03-2012, 07:27 PM,
#3
RE: Output voltage
Some output can be configured as open drain to drive 5 Vcc load.
Not yet supported in Pinguino, but it could be easily implemented ( with a #define for example ).

(08-03-2012, 03:15 PM)Dries Wrote: Is the output voltage of the Pinguino PIC32 OTG limited to 3.3V?
Or is there a way to get 5V out?
Can't find any information about the output voltages on the web.

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08-03-2012, 08:51 PM,
#4
RE: Output voltage
Yes. That won't raise the "output voltage" of the actual chip but it kind of is a way around it (as is using a relay or amplifier or solid state switch or ...).

John
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22-05-2012, 02:34 PM,
#5
RE: Output voltage
I have a quite similar problem: If I am right the default (main) Voltage of the Pinguino is 3.3V and it is mostly marked as VDD in the datasheed. With the use of open drain, all digital pins can provide up to 5V which is a voltage that is also accepted by all digital input pins (max. 5.5V)
But the analog and analog/digital pins only accept Voltages up to VDD + 0.03V = 3.33V. This can't be raised to 5V, can it? I am a bit confused with the use of "VDD" here, but as far as I have understood it VDD only means the Voltage used by the chip which is 3.3V here. This would mean that I can use 5V only for the digital input pins and would have to use the 3.3V pin to provide voltage for analog measurements with a potentiometer or something else.
On the other hand, do analog and analog/digital pins provide only 3.3V if they are used as output, or can you enable open drain here to?
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22-05-2012, 03:28 PM, (This post was last modified: 22-05-2012, 03:29 PM by pingotg.)
#6
RE: Output voltage
No it can't be raised to 5V.

All the limitations depend exactly on the actual chip and so vary between the various boards. You need to consult the Microchip datasheet carefully.

Be careful because recently Microchip found they had WRONGLY MARKED some pins as 5V-tolerant!! Use a current datasheet and do not rely on a schematic in case it uses the old data in that respect.

The datasheets each say which pins can be open drain (if you program them to be).

John
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22-05-2012, 04:28 PM,
#7
RE: Output voltage
(22-05-2012, 03:28 PM)pingotg Wrote: Be careful because recently Microchip found they had WRONGLY MARKED some pins as 5V-tolerant!! Use a current datasheet and do not rely on a schematic in case it uses the old data in that respect.

The datasheets each say which pins can be open drain (if you program them to be).

I have the Pinguino PIC32 and the current datasheed says the digital inputs are 5V tolerant, so I think it is better to use the analog/digital inputs with only 3.3V. If I connect 3.3V with a matching resistor to the analog input, the read value will give me an idea for which voltage the pin is designed, if it is 1023 the maximum voltage is likely to be 3.3V.
I'll post it when I am done with that.
Is my assumption right that VCC always is 3.3V on my Pinguino PIC32 and 5V is only for Digital Pins and powering components like engines, leds etc.?
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22-05-2012, 05:15 PM, (This post was last modified: 22-05-2012, 05:16 PM by pingotg.)
#8
RE: Output voltage
Please realise you must only trust the Microchip data (*). You seem to be trusting the Olimex data to be all you need, but it isn't.

I advise against making any assumptions Smile

Generally, any analog pin needs a reference voltage (often known as AREF) and I expect the max value corresponds to that.

(*) and your brain, as (like anyone) occasionally Microchip's technical authors make mistakes

John
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24-05-2012, 04:47 PM,
#9
RE: Output voltage
Well, then I think I have to read more technical datasheets Smile
The reference voltage AREF is 3.3V in the datasheets, so that should be the limit for the analog ports. Still had no time to measure the actual outputs and find out what the range of analog inputs is, hopefully the next days.
But what is the benefit of providing 5V supply on digital ports and accepting only 3.3V on analog ports? For the compability to Arduinos, a general 5V consistency would have been great.
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25-05-2012, 02:21 PM, (This post was last modified: 25-05-2012, 02:21 PM by pingotg.)
#10
RE: Output voltage
I expect that, because the silicon process is for 3.3V, Microchip could just have limited everything to 3.3V but decided any 5V would be better than that. Going further probably would have cost silicon area and that means money.

John
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