Hot!PIC18F2xK40 max output current

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Andy123
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2017/08/12 09:04:13 (permalink)
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PIC18F2xK40 max output current

I am looking at the datasheet for PIC18F24K40
http://ww1.microchip.com/downloads/en/DeviceDoc/40001843C.pdf
Page 533 listed max output current for digital I/O pin at +/-50mA that is unusually high.
Is this something that I can rely on or it would be better to check with support?
Usually this number is between 20 and 25 mA
 
If this is a true, then I can drive 40mA LED backlight without a transistor if I don't exceed total power dissipation.
This will simplify the design.
Thanks. 
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    mbrowning
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    Re: PIC18F2xK40 max output current 2017/08/12 09:18:19 (permalink)
    +1 (1)
    That's the ABSOLUTE max table, not operational characteristics. Operational characteristics are in parameters D360 and D370. I think some parts may have I/V curves where you can get typical output voltage at current, but this one doensn't have any such data (yet)
     
    ps - absolute max means if you exceed it you will likely damage the device.
    You could infer the output impedance from D360/D370 by dividing the voltage drop / rise from power/gnd by the current. This will give you a worst case output impedance to calculate how much current an output can drive/sink at a given voltage.
    post edited by mbrowning - 2017/08/12 09:31:44

    Mark
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    MBedder
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    Re: PIC18F2xK40 max output current 2017/08/12 09:29:37 (permalink)
    +1 (1)
    Do not mix up the Absolute Maximum Ratings with Electrical Specifications. See for example the similar specs from a non-preliminary datasheet of 18F25K80:
     
    Maximum output current sunk by PORTA<7:6> and any PORTB and PORTC I/O pins = 25 mA
    Maximum output current sunk by any PORTD and PORTE I/O pins = 8 mA
    Maximum output current sunk by PORTA<5:0> and any PORTF and PORTG I/O pins = 2 mA
    Maximum output current sourced by PORTA<7:6> and any PORTB and PORTC I/O pins = 25 mA
    Maximum output current sourced by any PORTD, PORTE and PORTJ I/O pins = 8 mA
    Maximum output current sourced by PORTA<5:0> and any PORTF, PORTG and PORTH I/O pins = 2 mA



    post edited by MBedder - 2017/08/12 09:31:08
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    Andy123
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    Re: PIC18F2xK40 max output current 2017/08/12 14:49:17 (permalink)
    +1 (1)
    I am coming from PIC18F23K22 and it has Max current 25mA Absolute Max:
    Maximum output current sunk by any I/O pin 25 mA
    Maximum output current sourced by any I/O pin 25 mA

    http://ww1.microchip.com/downloads/en/DeviceDoc/40001412G.pdf
    page 497 gives curves
    I was using it with 20mA for a quite some time with 5V power
     
    With K40 the Absolute Max is +/-50mA and I understand this is preliminary.
    Same for K42 parts, so this is not a typo.
     
    I have a feeling that they made changes and can handle a higher current. 
    For my design, I need not more than 40mA and assuming that datasheet is correct, it will not exceed Absolute Max
    post edited by Andy123 - 2017/08/12 14:53:42
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