Product category:
Microprocessors, Microcontrollers and DSPs
News Release from: Atmel Corporation | Subject: ATmega169P and ATmega165P
Edited by the Electronicstalk Editorial
Team on 21 March 2006
Microcontrollers sleep for years on a
battery
New microcontrollers incorporate a power-saving technology that provides multiyear battery-life in lighting control, security, keyless entry, ZigBee and other applications.
Atmel Corporation has released the first two AVR microcontrollers to incorporate a power-saving technology that provides multiyear battery-life in lighting control, security, keyless entry, ZigBee and other applications that spend most of their time in sleep mode The picoPower technology reduces "power-save" power consumption to as little as 650nA, even with the 32kHz clock running and superior brown-out detection, the industry's lowest
This article was originally published on Electronicstalk on 18 Nov 2005 at 8.00am (UK)
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The two picoPower devices now available are the ATmega169P with a 4x25 segment LCD controller, and the ATmega165P general purpose microcontroller.
Both microcontrollers have 16Kbyte of Flash memory, 512byte EEPROM and 1Kbyte SRAM.
They feature a 10bit ADC, USART, SPI, two-wire interface and operate from 1.8 to 5.5V with up to 16MIPS throughput.
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Fourteen additional 8bit picoPower AVR microcontrollers will be added within the next 12 months.
picoPower microcontrollers consume down to 340uA in active mode, 150uA in idle mode at 1MHz, 650nA in power-save mode and 100nA in power-down mode.
They will be pin-, performance- and code-compatible with existing AVR microcontrollers.
According to Asmund Saetre, Atmel's AVR Marketing Manager: "Multiple-year battery lives are becoming mandatory in a wide variety of applications".
"People don't really relish the idea of changing the battery in their car key or home HVAC system".
"Battery life has become so important that it is even a part of the ZigBee specification".
"ZigBee end-products must have a battery life of at least two years or they won't be certified".
"The systems for which we developed picoPower share one attribute; they spend most of their time doing nothing, but have features that draw unnecessary power even when they are in sleep mode".
"Although saving a few nanoamps here and there may not seem like a big deal, in systems that spend the vast majority of their time inactive, incremental improvements in sleep mode power consumption can add years to the battery life of the end product".
"Atmel has focused on eliminating or drastically reducing the power drain from oscillators, brownout detectors, I/O pin leakage and the like to achieve the lowest power MCUs on the market", Saetre concluded.
Atmel's picoPower technology utilises a variety of innovative techniques that eliminate unnecessary power consumption in power-down modes.
These include an ultra low power 32kHz crystal oscillator, automatic disabling and re-enabling of brown out detection (BOD) circuitry during sleep modes, a power reduction register (PRR) that completely powers down individual peripherals, and digital input disable registers that turn off the digital inputs to specific pins.
Many systems must keep track of time even when they are powered down.
Atmel has been optimised its 32kHz crystal oscillator to let the total power consumption of the device with a RTC be as low as 650nA.
Brownout detectors (BODs) detect when the power supply falls below the threshold required for operation and then issue a power-on reset to protect valuable data.
Without this protection, a power failure could cause catastrophic damage to the controller and make it inoperable.
The accuracy of BODs is directly proportional to the current they consume.
Low- or zero-power BODs tend to be both slow and inaccurate, while more accurate, faster BODs consume a lot of power.
As BODs usually remain on in sleep mode, they represent a substantial drag on battery life.
As a result, most vendors of ultra-low-power MCUs, sacrifice accuracy and speed to lower current consumption.
Atmel has taken a new approach, by creating a BOD with enough current to provide accurate detection at 1.8, 2.7 and 4.5V with 2us response time.
Power is saved by automatically disabling the BOD during sleep mode and re-enabling it when the controller wakes up - before it executes any instructions.
This approach provides superior protection with substantially less power drain.
Low pin-count MCUs frequently mix analogue-to-digital-conversion (ADC) and digital I/O on the same pins.
This can lead to current leakage through the digital I/O buffer.
Atmel has solved this problem with a dedicated input disable register (DIDR) that let the software disconnect all digital buffers from inputs that are used for ADC readings.
A power reduction register (PRR) on picoPower AVR MCUs contains control bits for disabling the entire clock distribution to unused peripheral modules.
The power reduction register is controlled by software that allows the user to turn on and off peripheral modules at any time.
The current state is frozen and all I/O registers are inaccessible when the peripheral module is disabled by the power reduction register.
When re-enabled, the peripheral module continues in the same state as before it was disabled.
Disabling one peripheral module results in a reduction of 5 to 10% of the total power consumption in active mode and 10 to 20% of the total power consumption in idle mode.
Atmel has also implemented dynamically configurable clock gating techniques that freeze the clock in parts of the circuit when they are not required.
On reactivation, the module restarts in the same state as before.
Clock-gating can also be used to reduce noise and improve the ADC performance in situations that require higher resolution measurements.
Conventional MCUs leave the Flash on during active mode, causing unnecessary static power consumption at low operating frequencies of a few megahertz or less.
AVR microcontrollers use a technique called Flash sampling that enables the Flash for a few nanoseconds to sample the array's contents and then immediately disables it, substantially reducing this source of current leakage.
The ATmega165P and the ATmega169P are available now in production quantities in 64-pin TQFP and 64-pin QFN packages.
ATmega165P is priced at $2.15 and ATmega169P with LCD controller is priced at $2.25 for 10,000 units.
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