ATmega128RFA1

Power Measurement

ATmega128RFA1

• SoC (uC and Transceiver)• Up to 16 MHz (i.e. almost 16 MIPS)• Voltage range: 1.8v to 3.6v• 16K bytes RAM• 128 K Flash• Zigbee compliant transceiver

ATmega128RFA1

• Transceiver– TX Power up to 3.5 dBm (2.24 mW)– Speed -> 250 kb/s and 500 kb/s, 1 Mb/s, 2 Mb/s– Security -> AES (128 bits)– RX current -> 12.5 mA – TX current -> 14.5 mA (max output power)

Power Control Features

• Power Reduction Registers– PRR0 (TWI, Timers, etc)– PRR1 (one bit to shutdown transceiver)– PRR2 (for disabling the four SRAM blocks)

• Watchdog Timer

• Brown-Out detect (BOD)

Important Peripherals

• Timers• ADC• TWI (I2C) -> RTC wake up• WDT (wakeup or reliability enhancement)• Transceiver

Sleep Current

• Power down mode (deep sleep)• All peripherals disabled– PRR0 = 0xFF– PRR1 = 0xFF

• WDT enabled

Current = 800 nA

Sense & Send: Cycle Time

3.44 ms

Sense & Send: TX Time

1.68 ms

Sense & Send: Sense Current

4.2 mA

Sense & Send: TX Current

15.6 mA

Life Time Estimate

• Ampere Hour– Sense -> 2.05 x 10-6 mAH– Tx -> 7.28 x 10-6 mAH– Total (sense & send) -> 9.33 x 10-6 mAH

• In ‘one hour’– # of Tx -> 450– Sense & Send -> 4.1985 x 10-3 mAH– Sleep -> 2.88 x 10-6 mAH– Total (sense, send & sleep) -> 4.2 x 10-3 mAH

Life Time Estimate

• For a battery of 200 mAH

– # of hours we get is

200/4.2 x 10-3

i.e. 47619 hrs

or about 5 years

Additional Possible Optimization

• Frequency scaling– Static– Dynamic

• Use of Real-Time Clock– Keep watchdog timer disabled in sleep mode• RTC chip takes less current than the WDT

– Wake up on RTC alarm interrupt• More flexible (not just max of 8 sec)