Nokia Customer Care TF5 Technical Information
Company Confidential TFE-4/RV-1
Issue 2.0 Mar/2005 Copyright © 2005 Nokia Corporation. Page 8a-21
Company Confidential
The SMPSon signal is set high (>4V) under two conditions, Powerok is high and ignition
sense is active or Powerok is high and B2Bpoweroffx is high. Both conditions are pro-
vided by D300 and V301. V302 is responsible for the level shifting of the 1.8V level pro-
vided by the phone engine to the 5V logic-level of D300. Further more, the level shifted
here, RS232POWEROFFX, which is the 4V translation of B2BPOWEROFFX signal, is gener-
ated here
Poweronx
Figure 15: Poweronx realization
The Poweronx function block generates a pulses of 0.5Hz, with a length of approximately
1 second high and 1 second low, when VEBpwr is active. The output voltage is 4.2V (like
VEBpwr)..
IGNS Level shifter
This block is responsible to translate the Ignition sense signal, which is 0n 12V level
(connected Car battery), to the 5V logic level for the startup logic and to 1.8V level for
the phone engine. The comparator N302 cares that the IGNS5V signal is only high when
the Sense input is higher than 9V level. The 1.8V level shifter is realized by voltage
divider R304/R307.
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