LP3947ISD-51 National Semiconductor, LP3947ISD-51 Datasheet - Page 7

• 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
LP3947 CHARGER OPERATION
The LP3947 charge cycle is initiated with AC adaptor or USB
power source insertion. If the voltage on the CHG-IN pin
meets under-voltage (V
TSHD
then pre-qualification cycle begins (see Figure 1). In this
cycle, a safe current level, less than 70mA, is pumped into
the battery while the voltage across the battery terminals is
measured. Once this voltage exceeds 3.0V, the controller
will initiate constant current fast charge cycle. If the CHG-IN
pin is connected to an AC adaptor, the default charge current
is 500 mA and I
parameter. If the CHG-IN pin is connected to the USB port,
constant current cycle will start with a default of 100 mA.
During this cycle, the 5.6 hr safety timer starts counting.
If the 5.6 hr safety timers times out during constant current
cycle, charging is terminated. As the battery is charged
during constant current mode, the voltage across pack ter-
minal increases until it reaches 4.2V (or 4.1V). As soon as
pack terminal reaches 4.2V (or 4.1V), the controller starts
operating in constant voltage mode by applying regulated
) requirements, and the Adaptor OK signal is detected,
2
C interface can be used to program this
UVLO-TSHD
), over-voltage (V
FIGURE 2. LP3947 with External Switch
OVLO-
7
V
the charge current, I
and when it drops below 0.1C (default value), the EOC
signal is activated indicating successful completion of the
charge cycle. The EOC current can be programmed to 0.1C,
0.15C, or 0.2C. The default value is 0.1C. After completing
the full charge cycle, the controller will start the maintenance
cycle where battery pack voltage is monitored continuously.
During the maintenance cycle, if the pack voltage drops 200
mV below the termination voltage, charge cycle will be initi-
ated providing that the wall adaptor is plugged in and is alive.
Charging terminates when the battery temperature is out of
range. For more explanation, please refer to “Ts Pin” section.
The LP3947 with I
selecting the charge current, battery regulation voltage and
EOC current. The LP3947 operates in default mode during
power up. See the “I
When charging source comes from the USB port, charging
starts with 100 mA (low power mode, ISEL = high). The USB
controller can set the ISEL pin low to charge the battery at
500 mA. A simple external circuit selects between an AC
adaptor or the USB port. The circuit is designed with priority
given to the AC adaptor.
BATT
voltage across the battery terminals. During this cycle,
2
C interface allows maximum flexibility in
2
CHG
C Interface” section for more detail.
, continues to decrease with time
20111006
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