is there sth. wrong with LPC1114

lpcware · ‎06-15-2016

Content originally posted in LPCWare by lxttian on Sat Oct 16 23:12:48 MST 2010
I had burn several LPC1114 in the circuit below.After I use it for hours, the PWM signal produce by LPC1114 became square wave limited between 3.3V and 2.5V. Is it possible that the LPC1114 is too unstable.Or the value of the resistor is not proper,or the may be sth. wrong with other parts of my circuit?
[B][/B]

Original Attachment has been moved to: 1100761_I2C.zip

lpcware · ‎06-15-2016

Content originally posted in LPCWare by lxttian on Mon Oct 18 02:19:42 MST 2010

Quote: rcazalis
Hi,

The high current pin is PIO0_7, not any pin?
I've also realised you don't use it as high current drive but high current sink... which is not what it is capable of.
In datasheet it says PIO0_7 can drive 20mA and sink 3 to 4mA.

You will most likely need to change your schematic : drive both diodes from the anode (and reduce resistor) or add two FET as Zero advised.

Romain

You can seethe figure 15 in LPC1114 datasheet;
Fig 15. Typical LOW-level output current IOL versus LOW-level output voltage VOL

if IOL represent the sink current,we can see it can sink current up to several mA.

And in fig 16,its standard pins can only drive several mA.

lpcware · ‎06-15-2016

Content originally posted in LPCWare by rcazalis on Sun Oct 17 23:50:29 MST 2010
Hi,

The high current pin is PIO0_7, not any pin?
I've also realised you don't use it as high current drive but high current sink... which is not what it is capable of.
In datasheet it says PIO0_7 can drive 20mA and sink 3 to 4mA.

You will most likely need to change your schematic : drive both diodes from the anode (and reduce resistor) or add two FET as Zero advised.

Romain

lpcware · ‎06-15-2016

Content originally posted in LPCWare by lxttian on Sun Oct 17 19:50:51 MST 2010

Quote: Zero
Did you try to change some of this values? I'm not sure, what you are trying to do.
Don't know the value of VCC1. If I should guess, I would blame your circuit:
If VCC1=3.3V and the LED costs about 1.2V (just guessing, don't know the exact value of TLP521) you are trying to switch your optocoupler with 2V/1000 Ohm = 2mA. That's not much. Don't know how you calculated this resistor, but my first idea would be to use a 680 Ohm resistor to increase the forward current.
Another optocoupler (with lower min. forward current like 6N138) could help also.
Of course LPC11xx can't draw currents like 10mA (to ensure a proper operation of LED / optocoupler), so it would be a good idea to use an additional transistor (or FET) to switch the LED (google for 'optocoupler input').

High-current output driver (20 mA) on one pin.
That is from the first page in LPC1114 datasheet, is that mean it can draw the same amount current ?

lpcware · ‎06-15-2016

Content originally posted in LPCWare by Ex-Zero on Sun Oct 17 02:00:20 MST 2010
Did you try to change some of this values? I'm not sure, what you are trying to do.
Don't know the value of VCC1. If I should guess, I would blame your circuit:
If VCC1=3.3V and the LED costs about 1.2V (just guessing, don't know the exact value of TLP521) you are trying to switch your optocoupler with 2V/1000 Ohm = 2mA. That's not much. Don't know how you calculated this resistor, but my first idea would be to use a 680 Ohm resistor to increase the forward current.
Another optocoupler (with lower min. forward current like 6N138) could help also.
Of course LPC11xx can't draw currents like 10mA (to ensure a proper operation of LED / optocoupler), so it would be a good idea to use an additional transistor (or FET) to switch the LED (google for 'optocoupler input').