TABLE 2. LED Indicator Summary

RED LED

(CHG)

GREEN LED

(EOC)

Charger Off

OFF

OFF

Charging Li Ion Battery*

ON

OFF

Maintenance Mode

OFF

ON

Charging Li Ion Battery after Passing Maintenance Mode

OFF

ON

EN Pin = LOW

OFF

ON

LDO Mode

OFF

OFF

5.6 Hr Safety Timer Flag/Battery Temperature Violation

ON

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

sion resistor should be used for R

is recommended for R

tional 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 10k

Ω 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

3. 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 oper-

ating at higher output currents, care must be taken not to

exceed the package power dissipation rating. See “Thermal

Performance of LLP Package” section for more detail.

Charger Status in Relation to Ts Voltage

Voltage on the Ts Pin

Charger Status

Ts

≥ 2.7V

LDO Mode

Voltage on the Ts Pin

Charger Status

2.427v

0V

≤ Ts ≤ 1.39V

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 “Ther-

mal Performance of LLP 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 Figures 5, 6. 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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