LP3947ISD-51 Datasheet, PDF (11/20 Pages) Texas Instruments – LP3947 USB/AC Adaptor, Single Cell Li-Ion Battery Charger IC

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LP3947
SNVS298B – NOVEMBER 2004 – REVISED APRIL 2013
V_CHG-IN
V_CHG-IN
0
V_CHG-IN
0
V_CHG-IN
0
0
4.1V
3.0V
0
0
Time
3.0V
0
0
Time
Load < 50 mA
Load > 50 mA
Figure 6. Power Up Timing Diagram in Charger Mode (1.39V < Ts < 2.427V)
V_CHG-IN
V_CHG-IN
0
V_CHG-IN
0
4.1V
0
V_CHG-IN
0
4.1V
0
0
Time
0
0
Time
Figure 7. Power Up Timing Diagram in LDO Mode (Ts ≥ 2.7V)
MODE PIN
The mode pin toggles the LP3947 between the AC adaptor mode and the USB mode. When CHG-IN is
connected to a USB port, this pin must be set low. When CHG-IN is connected to an AC adaptor, this pin must
be tied high to either the BATT pin or to the wall adaptor input. Caution: MODE pin should never be tied to CHG-
IN pin directly, as it will turn on an internal diode.
5.6 HR SAFETY TIMER IN CHARGER MODE
The LP3947 has a built-in 5.6 hr back up safety timer to prevent over-charging a Li Ion battery. The 5.6 hr timer
starts counting when the charger enters the constant current mode. It will turn the charger off when the 5.6 hr
timer is up while the charger is still in constant current mode. In this case, both LEDs will turn on, indicating a
fault condition.
When the battery temperature is outside the specified temperature range, the 5.6 hr safety timer will reset upon
recovery of the battery temperature.
I²C INTERFACE
I²C interface is used in the LP3947 to program various parameters as shown in Table 5. The LP3947 operates
on default settings following power up. Once programmed, the LP3947 retains the register data as long as the
battery voltage is above 2.85V.
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