LP3921 Datasheet, PDF (19/34 Pages) National Semiconductor (TI) – Battery Charger Management and Regulator Unit with Integrated Boomer® Audio Amplifier

VTERM[1]
0
0
1
1
TABLE 6. Charging Termination Voltage Control
VTERM[0]
0
1
0
1
Termination Voltage (V)
4.1
4.2 (Default)
4.3
4.4
TABLE 7. End Of Charge Current Control
PROG_EOC[1]
0
0
1
1
PROG_EOC[0]
0
1
0
1
End of Charge Current
0.1 (Default)
0.15C
0.2C
0.25C
Note: C is the set charge current.
TABLE 8. Charging Restart Voltage Programming
PROG_VRSTRT[1]
0
0
1
1
PROG_VRSTRT[1]
0
1
0
1
Restart Voltage(V)
V_TERM - 50 mV
V_TERM - 100 mV
V_TERM - 150 mV
V_TERM - 200 mV
TABLE 9. USB Charging Selection
USB_Mode_En
0
1
0
1
CHG_Mode_En
0
0
1
1
Mode
Fast Charge
Fast Charge
USB
USB
Current
Default or Selection
Default or Selection
100 mA
450 mA
Battery Charge Management
A charge management system allowing the safe charge and
maintenance of a Li-Ion battery is implemented on the
LP3921. This has a CC/CV linear charge capability with pro-
grammable battery regulation voltage and end of charge cur-
rent threshold. The charge current in the constant current
mode is programmable and a maintenance mode monitors for
battery voltage drop to restart charging at a preset level. A
USB charging mode is also available with 2 charge current
levels.
CHARGER FUNCTION
Following the correct detection of an input voltage at the
charger pin the charger enters a pre-charge mode. In this
mode a constant current of 50 mA is available to charge the
battery to 3.0V. At this voltage level the charge management
applies the default (100 mA) full rate constant current to raise
the battery voltage to the termination voltage level (default
4.2V). The full rate charge current may be programmed to a
different level at this stage. When termination voltage
(V_TERM) is reached, the charger is in constant voltage mode
and a constant voltage of 4.2V is maintained. This mode is
complete when the end of charge current (default 0.1C) is
detected and the charge management enters the mainte-
nance mode. In maintenance mode the battery voltage is
monitored for the restart level (4.05V at the default settings)
and the charge cycle is re-initiated to re-establish the termi-
nation voltage level. For start up the EOC function is disabled.
This function should be enabled once start up is complete and
a battery has been detected. EOC is enabled via register
CHGCNTL1, Table 10.
The full rate constant current rate of charge may be pro-
grammed to 19 levels from 50 mA to 950 mA. These values
are given in Table 5 and Table 13.
The charge mode may be programmed to USB mode when
the charger input is applied and the battery voltage is above
3.0V. This provides two programmable current levels of
100 mA and 450 mA for a USB sourced supply input at
CHG_IN. Table 9.
EOC
EOC is disabled by default and should be enabled when the
system processor is awake and the system detects that a
battery is present.
PROGRAMMING INFORMATION
TABLE 10. Register Address 8h'10: CHGCNTL1
BIT
NAME
FUNCTION
2
En_EOC Enables the End Of Charge current
level threshold detection. When set
to '0' the EOC is disabled.
The End Of Charge current threshold default setting is at
0.1C. This EOC value is set relative to C the set full rate con-
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