ATR2406_06 Datasheet, PDF (21/25 Pages) ATMEL Corporation – Low-IF 2.4-GHz ISM Transceiver

ATR2406
A successful packet exchange needs the following charge
Q = Q1 + Q2 + Q3 + Q4 + Q5 + Q6 + Q7 + Q8 + Q9 + Q10 = 192.47 µAs
As the described system is a FHSS system with 5 different channels, the system has to do this
up to five times before the packet is acknowledged by the base station. The average will be
2.5 times. In the case of an interfered environment, some more retries may be required; there-
fore, it is assumed the factor will be 3. The power-up time is included only once, as the cycle
will be completed without powering up and down the handheld in order to be as power efficient
as possible.
Average current needed for a packet exchange:
155 µAs + (37.5 µAs × 3) = 267.5 µAs
If the device will be used 1000 times a day →3.1 µA
Average current in active mode:
→ System Power Down current:
Current ATmega88:
Current ATR2406:
Current VREG (+ ShutDown):
1.25 µA
1.0 µA
2.75 µA
Assumed average power-down current is 5 µA.
→Overall power consumption is 8.1 µA
It is assumed the system uses a small battery with a capacity of 100 mAh. This is
100.000 µAh.
→Battery lifetime will be around: 12345 hours = 514 days = 1.4 years.
The most important factor is to get the power-down current as low as possible!
Example:
Assume a system where the handheld is used just 10 times per day.
→ I_active = 0.031 µA
and assuming the power-down current of this device is just 4 µA.
→I = 0.031 µA + 4 µA = 4.03 µA
→Battery lifetime will be around 24807 hours = 1033 days = 2.83 years.
→Power-down current is the main factor influencing the battery lifetime.
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4779L–ISM–09/06