LP3947ISD-51 National Semiconductor, LP3947ISD-51 Datasheet - Page 11

• Manufacturer Part Number: LP3947ISD-51
• Description: CHARGER, USB, I2C, POWERWISE, LLP-14
• Manufacturer: National Semiconductor

Specifications of LP3947ISD-51

• Battery Type: Li-Ion
• Input Voltage: 6V
• Battery Charge Voltage: 4.2V
• Charge Current Max: 750mA
• Battery Ic Case Style: LLP
• No. Of Pins: 14
• No. Of Series Cells: 1
• Operating Temperature Range: -40°C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Application Notes
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 con-
nected 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
FIGURE 5. Power Up Timing Diagram in Charger Mode (1.39V
FIGURE 6. Power Up Timing Diagram in LDO Mode (Ts ≥ 2.7V)
(Continued)
11
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 tem-
perature range, the 5.6 hr safety timer will reset upon recov-
ery of the battery temperature.
I
I
parameters as shown in Table 3. 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.
2
2
C INTERFACE
C interface is used in the LP3947 to program various
<
Ts
<
2.427V)
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