TFE-4/RV-1 Company Confidential
TF5 Technical Information Nokia Customer Care
Page 8a-20 Copyright © 2005 Nokia Corporation. Issue 2.0 Mar/2005
Company Confidential
Description of the HW Realization
Vcar-Check
Figure 13: Vcar-Check Realization
This block consists of two comparators, N300 and N301, which checks if the VCAR volt-
age is in the right operating range. When VCAR is in the right range both comparators
will have 5V(=Vwake) at the output. When the Vcar is over the limit of 15V N300 will
switch to ground level on output and Powerok will be forced low. The limit is determined
by R301/R306 and the reference level of 2.5V(=VWAKE/2) which is provided by the R305/
R300 combination.
Same happens when Vcar falls below 9V, in this Case the output of N301 will be forced
low and Powerok will be forced to ground. This limit is determined by the combination
R309/R310 and the 2.5V reference.
SMPS startup
Figure 14: SMPS startup realization
IGNS5V
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