USB Charger
For the USB charger, a switch-mode charging topology is used to efficiently step down the input voltage. As
with the wall charger, the USB charger starts in trickle mode with 80 mA charging current when the battery
voltage is less than 3.4V. When the battery voltage is equal 3.4V, the USB will go into enumeration mode.
USB charger shuts down during USB enumeration and it will be able to charge 450 mA after enumeration.
Dedicated USB can charge up to 1.0 A , depending on the particular host that the USB is connected to ( USB
1.1 = 80 mA, USB 2.0= 450 mA, dedicated charger = 1.0 A ).
The JUNO BB ASIC (D2800) will read the USB STAT1 and STAT2 signals from the LOVIISA PMU to check USB
status. The USB will configure the JUNO baseband as an A-device or B-device by checking the ID_OUT signal
from the PMU.
The DISCHRG signal controls the VBUS discharger.
Figure 39 USB charger
RM-497
System Module
Page 5 – 20 COMPANY CONFIDENTIAL Issue 1
Copyright © 2010 Nokia. All rights reserved.
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