BQ2406X Datasheet, PDF (16/31 Pages) Texas Instruments – 1A SINGLE-CHIP Li-Ion/Li-Pol CHARGE MANAGEMENT IC WITH THERMAL REGULATION

bq2406x
SLUS689 – JUNE 2006
bq2460X MODE
STANDBY
CHARGING
SUSPEND
SUSPEND
CHARGING, TMR PIN NOT OPEN
CHARGING, TMR PIN OPEN
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Table 4. Pre-Charge Timer Operational Modes
V(OUT) > V_(LOWV)
X
Yes
Yes
No
No
X
PRE-CHARGE TIMER MODE
RESET
RESET
RESET
SUSPEND
COUNTING, EXTERNAL PROGRAMMED RATE
RESET
In SUSPEND mode the pre-charge timer is put on hold (i.e., pre-charge timer is not reset), normal operation
resumes when the timer returns to the normal operating mode (COUNTING). If V(BAT) does not reach the
internal voltage threshold V_(LOWV) within the pre-charge timer period a fault condition is detected, the charger is
turned off and the pre-charge safety timer fault condition is latched.
When the pre-charge timer fault latch is set the charger is turned off. Under those conditions a small current
I_FAULT is applied to the OUT pin, as long as input power (IN) is detected AND V(OUT) < V_(LOWV), as part of a
timer fault recovery protocol. This current allows the output voltage to rise above the pre-charge threshold
V_(LOWV), resetting the pre-charge timer fault latch when the pack is removed. Table 5 further details the
pre-charge timer fault latch operation.
Table 5. Pre-Charge Timer Latch Functionality
PRE-CHARGE TIMER FAULT LATCHED WHEN
Pre-charge timer timeout AND V(OUT) > V_(PRECH)
PRE-CHARGE TIMER FAULT LATCH RESET AT
CE rising edge or OVP detected
Input power removed (not detected)
New charging cycle started; see state diagram
Timer function disabled
THERMAL PROTECTION LOOP
An internal control loop monitors the bq2406x junction termperature (T_J) to ensure safe operation under input
voltage transients, or unexpected printed circuit board temperature increase. This loop monitors the bq2406x
junction temperature and reduces the charge current when the IC junction temperature exceeds an internally set
reference temperature, T_J(REG), (112°C, typical). The bq2406x has a minimum charge current, I(MIN_TJ(REG)),
in thermal regulation (200 mA, typical). If the input voltage is set too high, the junction temperature exceeds the
regulation point and approaches thermal shutdown.
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