ATmega8515 power consumption

I am struggling to get the power consumption of sensor device down.
According to the datasheet (page 208, top graph), the ATmega8515 I use, uses
slightly less than 1mA @ 3.3V and 1MHz internal clock while active. But I
measure around 2.3mA. Even when I stop all I/O and go into an endless loop,
it still uses 2.1mA. Is Atmel showing off here or am I missing something?

Meindert

Meindert Sprang wrote:

> According to the datasheet (page 208, top graph), the ATmega8515 I use, uses
> slightly less than 1mA @ 3.3V and 1MHz internal clock while active. But I
> measure around 2.3mA. Even when I stop all I/O and go into an endless loop,

Did you hi-z all the GPIOs?
Did you measure current into Vcc pin _and_ current out of Vss pin?

"larwe" <zwsdotcom@gmail.com> wrote in message
news:1140005210.128403.246930@g43g2000cwa.googlegroups.com...
>
> Meindert Sprang wrote:
>
> > According to the datasheet (page 208, top graph), the ATmega8515 I use,
uses
> > slightly less than 1mA @ 3.3V and 1MHz internal clock while active. But
I
> > measure around 2.3mA. Even when I stop all I/O and go into an endless
loop,
>
> Did you hi-z all the GPIOs?

Yes, in fact, I disconnected ALL I/O's and enabled ALL pull-ups. So the only
active circuits where the VCC and GND connected to the power supply and one
pull-up resistor to the RST input. I'd call this a completely isolated AVR.

> Did you measure current into Vcc pin _and_ current out of Vss pin?

No but the Vss and Vss (GND) where the only connected pins, together with
the 10k pull up in RST.

Meindert

Meindert Sprang wrote:

> Yes, in fact, I disconnected ALL I/O's and enabled ALL pull-ups. So the only
> active circuits where the VCC and GND connected to the power supply and one
> pull-up resistor to the RST input. I'd call this a completely isolated AVR.

Any timers running? Worthwhile going down the peripherals list and
making sure everything is switched off.

Brownout detection enabled? Try turning it off.

"larwe" <zwsdotcom@gmail.com> wrote in message
news:1140011985.291845.151910@g14g2000cwa.googlegroups.com...
>
> Meindert Sprang wrote:
>
> > Yes, in fact, I disconnected ALL I/O's and enabled ALL pull-ups. So the
only
> > active circuits where the VCC and GND connected to the power supply and
one
> > pull-up resistor to the RST input. I'd call this a completely isolated
AVR.
>
> Any timers running? Worthwhile going down the peripherals list and
> making sure everything is switched off.

No timers, just one external interrupt, but I tested with interrupts
disabled.

> Brownout detection enabled? Try turning it off.

Makes no difference.

Meindert

[snip]
>
> Yes, in fact, I disconnected ALL I/O's and enabled ALL pull-ups. So the 
> only
> active circuits where the VCC and GND connected to the power supply and 
> one
> pull-up resistor to the RST input. I'd call this a completely isolated 
> AVR.
>
[snip]
>
If you "enabled ALL pull-ups" then it's not isolated. Each input pin held at 
0V will source nearly 0.1mA at vcc=3.3.

Peter

"Peter" <meltyb@hotmail.com> wrote in message
news:dsvd36$opp$1$8300dec7@news.demon.co.uk...
> If you "enabled ALL pull-ups" then it's not isolated. Each input pin held
at
> 0V will source nearly 0.1mA at vcc=3.3.

I wrote "Yes, in fact, I disconnected ALL I/O's and enabled ALL pull-ups".
Take that literally. I cut away all components on the board, leaving just
the power supply and the processor. So there is nothing left to pull a pin
down.

Meindert

Meindert Sprang wrote:

> I wrote "Yes, in fact, I disconnected ALL I/O's and enabled ALL pull-ups".
> Take that literally. I cut away all components on the board, leaving just
> the power supply and the processor. So there is nothing left to pull a pin

Starting to scrape the bottom of the barrel for answers here... but did
you program $FF into all the output latches (even for pins config'd as
input)?

"larwe" <zwsdotcom@gmail.com> wrote in message
news:1140014767.196794.18210@g14g2000cwa.googlegroups.com...
>
> Meindert Sprang wrote:
>
> > I wrote "Yes, in fact, I disconnected ALL I/O's and enabled ALL
pull-ups".
> > Take that literally. I cut away all components on the board, leaving
just
> > the power supply and the processor. So there is nothing left to pull a
pin
>
> Starting to scrape the bottom of the barrel for answers here... but did
> you program $FF into all the output latches (even for pins config'd as
> input)?

Yes, that is what I meant with "enabled ALL pull-ups" ;-)

Meindert

Meindert Sprang wrote:
> Yes, in fact, I disconnected ALL I/O's and enabled ALL pull-ups. So the only
> active circuits where the VCC and GND connected to the power supply and one
> pull-up resistor to the RST input. I'd call this a completely isolated AVR.

My bet would be on a peripheral that isn't disabled.

For the 8515 (pre-mega), Dave vanHorn has some resources here as a 
starting point to initialize all the peripherals: 
http://www.dvanhorn.org/Micros/Avr/Software.php

Or perhaps running the code in AVR Studio to see if the peripheral 
registers are all getting disabled.  (The emulator's not foolproof, of 
course, but it creates its share of "aha!" moments.)

Richard