User Manual

PCI Express MiniCard Hardware Integration Guide
28 Proprietary and confidential 213XXXX
Usage models
To calculate actual current consumption (and anticipated battery life), a usage
model is needed. As applications of the EM can vary widely, we can provide
only samples here.
Slotted mode sleep is assumed when not actively receiving or transmitting (SCI =
2).
Transmit power is assumed to be +3 dBm.
Table 4: Power consumption of a sample application
PDA with voice Field worker
(data only)
Remote data
logging
Upload (modem Tx)
20 e-mails / day
avg 5 kB each
1000 kB / day 40 kB / hr
Download (modem Rx)
40 e-mails / day
avg 5 kB each
500 kB web use
500 kB / day 100 kB / day
Coverage / data rate
1x / 80 kbps 1x / 80 kbps IS-95 / 14.4 kbps
Hours of operation
16 / day
(off 8 hrs / day)
8 / day
(off 16 hrs / day)
24 / day
Total power consumed over
24 hours
250 mAh 60 mAh 200 mAh
Back-power issues
Preventing back-power when the modem is off
Note: Without proper input protection, the modem may draw
sufficient current to remain powered, even when the normal
supply power is removed.
Active low signals may be deasserted (driven high) by the host when the modem
is not needed. This applies 3.0 V to the modem on these pins and presents the
risk of back-powering.
All connector inputs must be either high impedance (>20 kohm), or driven low,
when the modem is powered off. This is required to prevent back-powering the
modem.
USB signals can be driven while the modem is disabled.