LP3913 datasheet(38/70 Pages) TI1

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LP3913

SNVS489I – NOVEMBER 2006 – REVISED SEPTEMBER 2013

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CHCTL Register (01)h Charger Control Register

D7–6

D5–2

Access

Data

Termination voltage

ICC: Full Rate Charge

Charger enable

End of Charge Select

current

00: 4.1V (Li Ion)

0000: 100 mA

0: disabled

0: 5%

01: 4.2V (Li Polymer )

0001: 200 mA

1: enabled

1: 10%

10: 4.38V (Li Polymer)

0010: 300 mA

11: reserved

0011: 400 mA

0100: 500 mA

0101: 600 mA

0110: 700 mA

0111: 800 mA

1000: 900 mA

1001: 1000 mA

Reset

0000

Battery Charger Operating Modes

Pre-Qualification Mode

Lithium batteries cannot be subjected to a high current when the battery voltage is under a certain threshold,

otherwise the longevity of the battery would be compromised. Below this threshold of VFULLRATE, which typically

measures 2.85V, the charger circuit supplies a pre-qualification charge current. If the wall adapter is charging the

battery, the charger circuit supplies a constant current of 10% of the programmed charge current. If the USB is

charging the battery, the charger circuit supplies a constant 50 ma charge current. When the battery voltage

reaches VFULL_RATE, the charger transitions from pre-qualification to full-rate charging. In Pre-qualification mode,

the STAT2, STAT1, and STAT0 bits in the charger supervisory register are respectively low, low, high.

Full-Rate Charging Mode

The full-rate charge cycle is initiated following the successful completion of the pre-qualification mode. During

Full-Rate charging, the battery voltage steadily increases while charged with a constant current (CC). The three

charger status bits STAT2, STAT1 and STAT0 are respectively low, high, and low. The full-rate charge current is

selected using the Charge Control Register, which defaults to 100 mA.

It is recommended to charge Li-Ion batteries at a rate of 1C, where “C” is the capacity of the battery. As an

example, it is recommended to charge a battery with a capacity of 800 mAh at 800 mA, or 1C. Charging at a

higher rate may compromise the quality and lifetime of the battery.

Constant-Voltage (CV) Charging Mode

The battery voltage increases rapidly as a result of full-rate charging and once it reaches the programmable

termination voltage of either 4.1V, 4.2V or 4.38V, the charger will move to constant-voltage charge mode. During

this mode, the charge current gradually decreases while the battery remains at the termination voltage. The

termination voltage can be selected to be either 4.1V, 4.2V or 4.38V by programming bits D6 and D7 in the

Charger Control register to accommodate different battery chemistries. In CV charging mode, the Charge Control

Status bits STAT2, STAT1 and STAT0 are respectively logic 0, logic 1 and logic 1.

TOP-OFF Charging Mode

When the charge current reduces to the EOC threshold (programmable to 5% or 10% of programmed full rate

charge current), constant voltage charging will continue for an additional 21 minute TOP-OFF time period. In

TOP-OFF charging mode, the Charge Control Status bits STAT2, STAT1 and STAT0 are respectively logic 1,

logic 1 and logic 1. At the end of the TOP-OFF period, the charger transitions to Charge Cycle Complete.

Charge Cycle Complete

During Charge Cycle Complete, the charger is automatically disabled, regardless of the state of the Charge

Enable Bit. In Charge Cycle Complete, the STAT2, STAT1 and STAT0 bits are respectively logic 1, logic 0 and

logic 1. When the Battery Voltage drops below the VRESTART threshold, charging will resume in Full-Rate

Charging Mode.

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