Nokia 616 Service Manual page 187

Company Confidential TFE-4/RV-1
Nokia Customer Care TF5 Technical Information
Vcar Switch
The Vcar Switch is a power switch that can switch off the car battery voltage (Vcar) in
the front Vaudio- and the VEBpwr-regulators. It is used when RU is in standby mode. By
using this switch the leakage currents of those voltage regulators are less sensitive for
reaching the 1mA standby criteria. Now only this switch is leakage sensitive. The switch
is controlled by the SMPSON control line of the Power control/Reset Block. The leakage
can be verified by measurement of the Vcarsw voltage when the device is in standby
(SMPSON = off). Now the Vcarsw level has to be low (about 0V). This can be verified at
test point J113.
The SMPSon signal has values of about 0V during standby and 4V to 5V when powered
up. In this case, Vcarswitch has to guarantee low serial resistance to minimize the heat
dissipation within V104. This can be verified by applying 3A load at VEBPWR and mea-
suring Vcarsw in this case.
SMPSON
Figure 8: HW-Realization of Vcar Switch
VAudio
The power supply VAudio is used to supply the power amplifier for the HF speaker. It is
designed by using low drop-regulator. Even when car voltage falls below 10V, it shall
provide a slidely reduced Voltage level against Vcar on VAudio power line.
Copyright © 2005 Nokia Corporation.
Issue 2.0 Mar/2005 Page 8a-15
Company Confidential