Datasheet

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hiRef
loRef
Ts
Logic
charger
control
ntc
LM3658
SNVS328E –MAY 2005–REVISED MARCH 2007 www.ti.com
Charger Timer (T
CHG
)
The charge timer starts with the initiation of full-rate charging and has a duration of 5 hours for the LM3658. If the
charge current does not reach EOC, charging stops and STAT1 and STAT2 both turn on to indicate a bad
battery status. Once the charge control declares a bad battery, removing the input source is the only means to
clear the bad battery status.
Top-Off Timer (T
TOPOFF
)
Once the charger successfully completes constant current constant voltage charging, it enters top-off mode and
starts T
TOPOFF
timer. Topoff lasts 30 minutes for the LM3658. During top-off, charging stops when T
TOPOFF
reaches its count or when I
CHG
reaches 2.5% of the full-rate charge current. There is no time-out condition in top-
off mode.
When charging is interrupted either by battery temperature out of range or disabling the LM3658, the applicable
safety timer will store its count value for the duration of the interruption and subsequently resumes counting from
its stored count value when charging continues, only if the charger resumes to the same operation mode it was
in before the interrupt.
The LM3658SD-A version has selectable timers for T
CHG
and T
TOPOFF
. Based on the logic level applied to the
USB_sel pin, timers can be chosen as follow:
Input USB_SEL T
PREQUAL
T
CHG
T
TOPOFF
CHG_IN Low 30 minutes 10 hours 60 minutes
CHG_IN High 30 minutes 5 hours 30 minutes
USBpwr Low 30 minutes 10 hours 60 minutes
USBpwr High 30 minutes 5 hours 30 minutes
BATTERY TEMPERATURE MONITORING (SUSPEND MODE)
The LM3658 is equipped with a battery thermistor interface to continuously monitor the battery temperature by
measuring the voltage between the T
S
pin and ground. Charging is allowed only if the battery temperature is
within the acceptable temperature range set by a pair of internal comparators inside the LM3658. If the battery
temperature is out of range, STAT1 and STAT2 both turn off and charging is suspended. Timer holds its count
value.
The TS pin is only active during charging and draws no current from the battery when no external power source
is present.
If the TS pin is not used in the application, it should be connected to GND through 10kΩ pulldown resistor.
When the TS pin is left floating (battery removal), then the charger will be disabled as the TS voltage exceeds
the upper temperature limit.
The LM3658 battery temperature feature is tailored to use negative temperature coefficient (NTC) 103AT
thermistors with 10kΩ impedance. If alternative thermistors need to be used in the system, supplemental external
resistors are needed to create a circuit with equivalent impedance.
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