LP3921 Datasheet, PDF (24/41 Pages) National Semiconductor (TI) – Battery Charger Management and Regulator Unit with Integrated Boomer® Audio Amplifier

LP3921
SNVS580A – AUGUST 2008 – REVISED MAY 2013
Table 15. Register Address 8h'13: CHGSTATUS1 (continued)
BIT
NAME
FUNCTION (if bit = '1')
0
PRECHG
Set during precharge.
Charger Status Register 2 Read only
Table 16. Register Address 8h'13: CHGSTATUS2
BIT
NAME
FUNCTION (if bit = '1')
1
Tout_ConstV
Set after timeout in CV phase.
0
BAD_BATT
Set at bad battery state.
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IMON CHARGE CURRENT MONITOR
Charge current is monitored within the charger section and a proportional voltage representation of the charge
current is presented at the IMON output pin. The output voltage relationship to the actual charge current is
represented in the following graph and by the equation:
V_IMON(mV) = (2.47 x I_CHG)(mA)
1.729
1.235
0.247
100
500
700
CHARGE CURRENT (mA)
Figure 8. IMON Voltage vs. Charge Current
Note that this function is not available if there is no input at CHG_IN or if the charger is off due to the input at
CHG_IN being less than the compliance voltage.
LDO Information
OPERATIONAL INFORMATION
The LP3921 has 7 LDO's of which 3 are enabled by default, LDO's 1,2 and 3 are powered up during the power
up sequence. LDO's 4, 5 and 6 are separately, externally enabled and will follow LDO2 in start up if their
respective enable pin is pulled high. LDO2, LDO3 and LDO7 can be enabled/disabled via the serial interface.
LDO2 must remain in regulation otherwise the device will power down. While LDO1 is enabled this must also be
in regulation for the device to remain powered. If LDO1 is disabled via I²C interface the device will not shut down.
INPUT VOLTAGES
There are two input voltage pins used to power the 7 LDO's on the LP3921. V_IN2is the supply for LDO3, LDO4,
LDO5, LDO6 and LDO7. V_IN1is the supply for LDO1 and LDO2.
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