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3. TECHNICAL BRIEF
Trickle Charge Current
When the battery voltage is below the minimum battery voltage VMIN given in the electrical specification,
the charger operates in a trickle/preconditioning mode, where the charge current is typically 14% of the
programmed charge current for the cradle input. If power comes from the USB input, the trickle mode
current is approximately 53mA.
End-of-Charge Indication
The CHG pin internal open-drain MOSFET turns off when the charge current falls below the IMIN threshold,
which is programmable for the cradle input and fixed for the USB input. Once the end-of charge-current is
reached, the CHG status will be latched. The latch can be reset at one of the following conditions:
1. The part is disabled and re-enabled
2. The selected input source has been removed and reapplied
3. The USBON turns LOW and turns back to HIGH for the USB input
4. The BAT pin voltage falls below the CV mode threshold Regardless of the CHG pin status, however, the
charger does not turn off as long as an input power source is attached.
Power Presence Indication
When either the USB or the cradle input voltage is above the POR threshold, the PPR pin internal open-
drain MOSFET turns on indicating the presence of input power.
Power-Good Range
Even if there is a power present, the charger will not deliver any current to the output if the powergood
conditions are not met. The following two conditions together define the power-good voltage range:
1. VCDRL or VUSB > VPOR
2. VCDRL or VUSB - VBAT > VOS
where the VOS is the offset voltage for the input and output voltage comparator, discussed shortly.
Both VPOR, VOS have hysteresis, as given in the Electrical Specification table.
The charger will not charge the battery if the input voltage does not meet the power-good conditions.
Thermal Foldback (Thermaguard™)
The thermal foldback function reduces the charge current when the internal temperature reaches the
thermal foldback threshold, which is typically 100°C. This protects the charger
from excessive thermal stress at high input voltages.
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