LP3923_15 Datasheet, PDF (19/37 Pages) Texas Instruments – Cellular Phone Power Management Unit

LP3923
www.ti.com
SNVS567B – APRIL 2010 – REVISED MAY 2013
If the battery is deeply depleted and the overdischarge protection circuit is active, during startup the charger may
detect that the battery is not present. This can cause the charger to select a non-default charging current (LDO
mode default charging current).
CHARGER FUNCTION
Following the correct detection of an input voltage at the charger pin the charger enters a pre-charge mode. In
this mode a constant current of 50 mA is available to charge the battery to 2.8V. At this voltage level the charge
management applies the full rate constant current to raise the battery voltage to the termination voltage level
(default 4.2V). The full-rate charging current may be programmed to a different level at this stage. When
termination voltage (VTERM) is reached, the charger is in constant voltage mode and a constant voltage of 4.2V
is maintained. This mode is complete when the end of charging current (default 0.15C) is detected and the
charge management enters the maintenance mode. In maintenance mode the battery voltage is monitored for
the restart level (default VTERM - 100 mV) and the charge cycle is re-initiated to re-establish the termination
voltage level.
THERMAL SHUTDOWN
The Thermal Shutdown (TSD) function monitors the chip temperature to protect the chip from temperature
damage caused, for example, by excessive power dissipation. If the temperature exceeds a higher threshold
value of +160°C, the TSD_H bit in the Register 0x0C is set, and the chip will automatically run the Power Down
sequence.
The restart operation after Thermal Shutdown can be initiated only after the chip has cooled down to the +90°C
threshold. The APU_TSD_EN bit in the Register 0x1C is controlling the restart. If this bit is cleared (default) then
a Power On sequence is initiated normally through PWR_ON, CHG_IN or VBUS. If APU_TSD_EN is written to
logic 1 then an automatic Power Up sequence is initiated. All register settings preserved in such case. Power On
can be activated only if the junction temperature is less than the early warning lower threshold +90°C.
The temperature monitoring function has two charger threshold values that result in protective actions. When a
lower threshold of +105°C is exceeded, the TSD_L bit in Register 0x0C will be set, bit will reset it if the
temperature has decreased to lower than 15°C below the threshold.
When a upper charger threshold of +115°C is exceeded, the charger will reduce charging current to protect the
chip.
Parameter
Typ
Higher Threshold⁽¹⁾
160
Charger Early Warning⁽¹⁾
105
Early Warning Hysteresis⁽¹⁾
15
Charger Thermal Regulation
115
(1) Ensured by design.
Unit
°C
°C
°C
°C
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