LP3947ISD-51 Datasheet, PDF (10/20 Pages) Texas Instruments – LP3947 USB/AC Adaptor, Single Cell Li-Ion Battery Charger IC

LP3947
SNVS298B – NOVEMBER 2004 – REVISED APRIL 2013
Table 3. LED Indicator Summary
Charger Off
Charging Li Ion Battery⁽¹⁾
Maintenance Mode
Charging Li Ion Battery after Passing Maintenance Mode
EN Pin = LOW
LDO Mode
5.6 Hr Safety Timer Flag/Battery Temperature Violation
RED LED
(CHG)
OFF
ON
OFF
OFF
OFF
OFF
ON
(1) Charging Li Ion battery for the first time after V_CHG-IN insertion.
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GREEN LED (EOC)
OFF
OFF
ON
ON
ON
OFF
ON
Ts PIN
The LP3947 continuously monitors the battery temperature by measuring the voltage between the Ts pin and
ground. Charging stops if the battery temperature is outside the permitted temperature range set by the battery’s
internal thermistor R_T and the external bias resistor R_S. A 1% precision resistor should be used for R_S. A curve 2
type thermistor is recommended for R_T. The voltage across R_T is proportional to the battery temperature. If the
battery temperature is outside of the range during the charge cycle, the LP3947 will suspend charging. As an
example, for a temperature range of 0°C to 50°C, a 10kΩ for the thermistor and a 4.1kΩ for R_s should be used.
When battery temperature returns to the permitted range, charging resumes from the beginning of the flow chart
and the 5.6 hr safety timer is reset. Refer to Figure 4. LP3947 Charger Flow Chart for more information.
In absence of the thermistor, Ts pin will be pulled high to VT and the LP3947 goes into LDO mode. In this mode,
the internal power FET provides up to 1.2 amp of current at the BATT pin. The LDO output is set to 4.1V or 4.2V,
depending on the programmed battery regulation voltage. When operating at higher output currents, care must
be taken not to exceed the package power dissipation rating. See “Thermal Performance of WSON Package”
section for more detail.
Table 4. Charger Status in Relation to Ts Voltage
Voltage on the Ts Pin
Ts ≥ 2.7V
2.427v ≤ Ts < 2.7V
0V ≤ Ts ≤ 1.39V
1.39V < Ts < 2.427V
Charger Status
LDO Mode
Charger Off
Charger On
LDO MODE
The charger is in the LDO mode when the Ts pin is left floating. This mode of operation is used primarily during
system level testing of the handset to eliminate the need for battery insertion. CAUTION: battery may be
damaged if device is operating in LDO mode with battery connected.
The internal power FET provides up to 1.2 amp of current at BATT pin in this mode. The LDO output is set to
4.1V. When operating at higher output currents, care must be taken not to exceed the package power dissipation
rating. See “Thermal Performance of WSON Package” section for more detail.
EN PIN
The Enable pin is used to enable/disable the charger, in both the charger mode and the LDO mode, see Figure 6
Figure 7. The enable pin is internally pulled HIGH to the CHG-IN pin. When the charger is disabled, it draws less
than 4 µA of current.
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