LP3947ISD-51 National Semiconductor, LP3947ISD-51 Datasheet - Page 9

• 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

AC Adaptor Mode
USB Mode
Application Notes
CHARGE CURRENT SELECTION IN CONSTANT
CURRENT MODE
In the AC adaptor mode, the LP3947 is designed to provide
a charge current ranging from 100 mA to 750 mA, in steps of
50 mA, to support batteries with different capacity ratings.
The default value is 500 mA. No external resistor is required
BATTERY VOLTAGE SELECTION
The battery voltage regulation can be set to 4.1V or 4.2V by
default. Please refer to the Ordering Information table for
more detail.
END OF CHARGE (EOC) CURRENT SELECTION
The EOC thresholds can be programmed to 0.1C, 0.15C or
0.2C in the LP3947. The default value is 0.1C, which pro-
vides the highest energy storage, but at the expense of
longer charging time. On the other hand, 0.2C takes the
least amount of charging time, but yields the least energy
storage.
Monitoring the Diff Amp output during constant voltage cycle
can provide an accurate indication of the battery charge
status and time remaining to EOC. This feature is particularly
useful during constant voltage mode. The current sense
circuit is operational in the LDO mode as well. It can be used
to monitor the system current consumption during testing.
HIGH
HIGH
LOW
LOW
MODE Pin
TABLE 1. Charge Current Selection in AC Adaptor/USB Mode
(Continued)
FIGURE 4. Charge Current Monitoring Circuit (Diff-Amp)
HIGH
LOW
HIGH
LOW
ISEL Pin
ISEL polarity is irrelevant. Default 500 mA charge current. Can be
reprogrammed via I
100 mA charge current
Default 500 mA charge current. Can be reprogrammed via I
9
to set the charge current in the LP3947. In the USB mode,
the LP3947 will initially charge with 100 mA (ISEL = high). By
setting the ISEL pin low, charge current can be programmed
to 500 mA. In addition, with ISEL = low, the charge current
can be programmed to different values via the I
CHARGE CURRENT SENSE DIFFERENTIAL AMPLIFIER
The charge current is monitored across the internal 120 mΩ
current sense resistor. The differential amplifier provides the
analog representation of the charge current. Charge current
can be calculated using the following equation:
Where voltage at Diff Amp output (V
charge current (I
LED CHARGE STATUS INDICATORS
The LP3947 is equipped with two open drain outputs to drive
a green LED and a red LED. These two LEDs work together
in combinations to indicate charge status or fault conditions.
Table 2 shows all the conditions.
2
C.
Functions
CHG
) is in amps.
20111009
DIFF
2
C.
) is in volt, and
2
C interface.
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