Electronic Guru help...!

x in the city

Hi Guys..



I am wondering if I go about making either of these systems..........

http://www.atmel.com/dyn/resources/prod_documents/DOC0597.PDF


http://www.atmel.com/dyn/resources/prod_documents/DOC0524.PDF

would the Vcc voltage be constant (stable) while it goes about its tasks or driving the ADC, Termo....?

Reason being is I want to have some control over the Vcc of the mcu (with a buck converter cum programmable supply) and have 'smart' intelligence commands sent from the mpu to the buck requesting specific voltages depending in its activity.

I am aware that the current/voltages might be minimal, but it doesnt matter too much, the main thing is to have some communication between the mpu and the power source.


Ideally, I would like to have the mpu perform intensive operations with huge fluctuations in the current and or voltage.

.......if you made it this far, well done..

Cheeble

x in the city wrote: »

would the Vcc voltage be constant (stable) ....?

Vcc will be constant/stable within the capabilities of the voltage regulator.

Not quite sure this is the answer you were looking for?

Cheeble-eers

FarmerGreen

Li-Po battery and monitor charge state to determine level of processor activity.

x in the city

Li-Po battery and monitor charge state to determine level of processor activity.

?

can you explain this a bit more?

Can I perform internal tasks that will use up a lot of current and thus alter the vcc rail anyone know?

such as an ALU or something....

its the control of the vcc rail which is key,,,..!

Cheeble

Can I perform internal tasks that will use up a lot of current and thus alter the vcc rail anyone know?

That depends almost entirely on the power supply.

If you've a stiff Vcc rail then no. If you've a poor regulator then yes.

Cheeble-eers

backboiler

Clarifying your aim will help get you a useful answer
Are you trying to demonstrate that the current changes with different operations?
If so you may be better investigating the low-power modes of the CPU. Alternatively you could have a variable-speed external oscillator feeding the CPU's clock input. CMOS gates only really use power when switching so if you slow down the CPU clock you get lower power consumption. Data sheet say it can go all the way down to 0 Hz but it'll not control much at that speed :cool:
Changing the actual supply voltage mid-operation is not a good idea as it may cause the CPU's power supply monitoring circuitry to flag a brown-out condition and reset.

spideog7

Isn't the uC meant to have a fairly constant supply voltage? I think this is especially important for A/D conversion cause it's used as a reference?

Also most uC can be setup to sleep themselves when they aren't required, so they'll drop to a minimal supply current and wait for an interrupt.

x in the city

backboiler wrote: »

Clarifying your aim will help get you a useful answer
Are you trying to demonstrate that the current changes with different operations?
If so you may be better investigating the low-power modes of the CPU. Alternatively you could have a variable-speed external oscillator feeding the CPU's clock input. CMOS gates only really use power when switching so if you slow down the CPU clock you get lower power consumption. Data sheet say it can go all the way down to 0 Hz but it'll not control much at that speed :cool:
Changing the actual supply voltage mid-operation is not a good idea as it may cause the CPU's power supply monitoring circuitry to flag a brown-out condition and reset.

ya, I know all that but what I wish to do is have some intelligence so that the cpu/mpu knows when to slow down the clock etc..

at the moment i am getting an atmel can dev board with i2c

going to hook it up to a lp3907 ic which is a dc/dc programmable ic.

i can specify outputs on it from the mpu

next stage is have a load attached to the lp3907 output(s)
and see if i can manage them accodrig to activity going on etc...

x in the city

spideog7 wrote: »

Isn't the uC meant to have a fairly constant supply voltage? I think this is especially important for A/D conversion cause it's used as a reference?

Also most uC can be setup to sleep themselves when they aren't required, so they'll drop to a minimal supply current and wait for an interrupt.

intels use a vrd system to communicate requirements to a dc/dc buck converter via VID codes

if the system was put into hibernate is may for example tell the buck regulator to send me 800mv, im going to sleep...(this is sent from the vid codes)

delux

would the Vcc voltage be constant (stable) while it goes about its tasks or driving the ADC, Termo....?

The output of the regulator would be constant unless the system draws more current than the max allowed. If that happened the regulator output would drop which is not what you want. That's why regulators have different ratings, you choose a rating well above what you need.

ya, I know all that but what I wish to do is have some intelligence so that the cpu/mpu knows when to slow down the clock etc..

To slow down the clock you would need to use a micro with an internal oscillator or use an external crystal for the primary oscillator and a slow crystal for the secondary oscillator. But the micro would need to support clock switching for this to work.

Also most uC can be setup to sleep themselves when they aren't required, so they'll drop to a minimal supply current and wait for an interrupt.

This is what most designers do to lower power. Have you checked the electrical specs for the micro? There is a huge different between active and powerdown currents. There is a minimal difference between active currents with VDD set to different levels - is it really worth the trouble????!

..for example tell the buck regulator to send me 800mv

I'm not sure any ATMELs will allow VDD down to 800mV. Probably something like 1.8V minimum. If you drop VDD down to 800mV you're in undefined territory and the micro will most likely not run when you raise VDD unless you bring it down to 0V first.

If you're copying those app notes with the LCDs or segment displays you could lower system power by cutting power to the LCD/segment display with MOSFETs when they are not being used.