On Wed, 22 Dec 2010 17:55:30 +0000 (UTC), zipwize said:
> Recently I had to get sleep mode to work for the PIC16F688. I have MCLR
> set as internal. I'm using the internal RC oscillator. I have two outputs
> going to transistors to drive LED's. I have two switch inputs with pull
> up resistors. I'm running the device from 3 type 675 coin batteries. I
> had so much trouble getting the current down. I was getting hundreds of
> uA. It would float all over the place from 1.2mA to 100uA. Finally I
> discovered that if I connect about 5K I could get the sleep mode current
> down to 70nA. It was consistant. I'm using wake up on pin change and I
> only have the two switch inputs enabled. I set all the other pins as
> input. I have nothing else connected. I use ICSP with a ICD-3. I fixture
> the tiny board with probes to connect the ICSP pins.=20
>=20
> If MCLR is internal, why do I have to tie it low to get low sleep
> current? Is there a better way?=20

You need to set unused pins as outputs or else tie them to + or ground.
You can use internal pullups, floating inputs draw current. However I
don't think MCLR has one on the '688 so it definitely must be tied
somewhere.

Bob

--=20
http://www.fastmail.fm - Email service worth paying for. Try it for free

--=20
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.