0

0

Time

Time

0

0

4.1V

0

0

0

4.1V

0

VCHG-IN

VCHG-IN

VCHG-IN

VCHG-IN

Load < 50 mA

Load > 50 mA

0

0

Time

Time

0

0

4.1V

3.0V

0

VCHG-IN

0

VCHG-IN

0

3.0V

0

VCHG-IN

VCHG-IN

LP3947

www.ti.com

SNVS298B – NOVEMBER 2004 – REVISED APRIL 2013

Figure 6. Power Up Timing Diagram in Charger Mode (1.39V < Ts < 2.427V)

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.

I

2C 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.

Copyright © 2004–2013, Texas Instruments Incorporated

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Product Folder Links: LP3947