LP3913 Datasheet, PDF (38/70 Pages) Texas Instruments – Power Management IC for Flash Memory-Based Portable Media Players

LP3913
SNVS489I – NOVEMBER 2006 – REVISED SEPTEMBER 2013
CHCTL Register (01)h Charger Control Register
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Access
Data
Reset
D7–6
rw
Termination voltage
00: 4.1V (Li Ion)
01: 4.2V (Li Polymer )
10: 4.38V (Li Polymer)
11: reserved
01
D5–2
I_CC: Full Rate Charge
current
0000: 100 mA
0001: 200 mA
0010: 300 mA
0011: 400 mA
0100: 500 mA
0101: 600 mA
0110: 700 mA
0111: 800 mA
1000: 900 mA
1001: 1000 mA
0000
D1
Charger enable
0: disabled
1: enabled
1
D0
End of Charge Select
0: 5%
1: 10%
1
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 V_FULLRATE, 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 V_{FULL_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 V_RESTART threshold, charging will resume in Full-Rate
Charging Mode.
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