Voltage is measured with Fluke DVM and oscope for noise/level tracking. I
can reproduce using a stabilized variable power source, or a dedicated LDO.

I use 5x100nF low ESR ceramic capacitors for bypass all VDD + AVDD pins.
In addition to that, the VCAP is 10uF tantalum but tested with 10uF ceramic
too.

All GND, VDD and pins are depicted with best layout practices, etc.
In fact, this happens even if I program the official PIM in the Explorer 16
with Pickit3, so I do not think is the circuit.

Regards,
Ariel Rocholl



On Tue, Mar 11, 2014 at 1:46 PM, <alan.b.pearce@stfc.ac.uk> wrote:

> > I've been using devices from this family for a while and all them,
> according to
> > my experience with PICKIT3, seems to require at least 3.5VDC while bein=
g
> > programmed, otherwise fail to program. Sometimes I can get them to
> > program as low as 3.35VDC but most of the time they won't, whereas 3.5V=
DC
> > seems to be good enough 90% of the time. I've never been able to progra=
m
> > these parts with 3.0VDC which is within specs.
> >
> >
> > The programmer used is PICKIT3 with external power in a circuit, but
> behaves
> > the same if I connect an isolated device to PICKIT3 itself, using self
> power or
> > external power. No difference.
> >
> >
> >  The microchip programming specification for these parts is 3.0-3.6V
> > (parameter D111 on DS70619B document) with an instantaneous current
> > during programming of 200mA (parameter D114). Looking into the errata f=
or
> > these parts does not mention anything regarding programming voltages th=
at
> > could lead to think this is a known issue.
>
> My response would be to ask how you are measuring the voltage.
>
> Using the PicKit3? This, to me, would be a highly suspect way to do it.
>
> A DVM at the chip itself? This would be the best way, especially if it is
> a known calibrated DVM, and ideally has a max/min function like the Fluke
> 89 IV or similar meters, which will track the voltage changes and allow y=
ou
> to read them out later.
>
> How is the PCB arranged? Planes for both Vcc & Gnd, with recommended caps
> on all power pins? Note that the Vcap pin MUST have the recommended cap
> value on it. IIRC the recommended value is 10uF ceramic or other low ESR,
> although IIRC they do say you can go to 4.7uF. I do seem to remember this
> issue coming up in the Microchip forums, and this being a MUST DO.
> --
> Scanned by iCritical.
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