LP3913 Datasheet, PDF (37/70 Pages) Texas Instruments – Power Management IC for Flash Memory-Based Portable Media Players

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Adapter
USB
VDD
CHG_DET
USBPWR
LP3913
SNVS489I – NOVEMBER 2006 – REVISED SEPTEMBER 2013
Q1
Q2
VBATT
Li-Ion Cell
Charge Status Indication
Two LEDs connected to the LP3913 are used to indicate the status of the charging. The CHG pin is connected to
a red LED that is enabled when an external power source is connected and the battery is charging. The second
STAT pin is connected to a green LED. When the battery charging transitions from CC to CV mode, then the
green LED is blinking with a 50% duty cycle and a period of 1 second. When the battery is fully charged, then the
green LED is always on.
Both LEDs are off when there is no external power connected.
Table 3. Truth Table for the LED Status Indicators
Condition
No Charger or USB
Charger off
Pre-Qualification
Constant Current CC
Constant Voltage CV
EOC / Top-OFF charging
Charge cycle complete
ERROR (Battery Temp, Thermal shutdown)
Safety Timer Expired
RED LED
OFF
ON
ON
ON
ON
ON
ON
50% duty cycle
50% duty cycle
GREEN LED
OFF
OFF
OFF
OFF
50% duty cycle
ON
ON
OFF
OFF
50% duty cycle indicates the LED is pulsed on/off for equal times at a frequency of 1 Hz.
The RED pin and GREEN pin are connected to a regulated driver to ensure that the brightness is independent
from the external power. The LEDs need to be connected between the CHG / STAT pins and GND.
Thermal Charger Power FET Regulation
The internal power FET Q2 in the linear charger module is thermally regulated to the junction temperature of
115°C to ensure optimal charging of the battery. The charge current is limited by the charge current selected in
the Charger Control Register but is also thermally limited to prevent the junction from overheating during high
charge currents at high ambient temperatures as the package power dissipation is limited.
Thermal regulation ensures maximum charge current and superior charge rate without exceeding the power
dissipation limits of LP3913.
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