BQ2406X Datasheet, PDF (21/31 Pages) Texas Instruments – 1A SINGLE-CHIP Li-Ion/Li-Pol CHARGE MANAGEMENT IC WITH THERMAL REGULATION

bq2406x
www.ti.com
SLUS689 – JUNE 2006
CHARGE SAFETY TIMER
As a safety mechanism the bq2406x has a user-programmable timer that monitors the total fast charge time.
This timer (charge safety timer) is started at the end of the pre-conditioning period. The safety charge timeout
value is set by the value of an external resistor connected to the TMR pin (R_TMR); if pin TMR is left open
(floating) the charge safety timer is disabled.
The charge safety timer time-out value is calculated as follows:
T_(CHG) = [K_(CHG)× R_(TMR)]
The safety timer operation modes are shown in Table 7
Table 7. Charge Safety Timer Operational Modes
bq2460X
STANDBY
CHARGING
SUSPEND
SUSPEND
CHARGING, TMR PIN NOT OPEN
CHARGING, TMR PIN OPEN
V(OUT) > V_(LOWV)
X
No
No
Yes
Yes
X
CHARGE SAFETY TIMER MODE
RESET
RESET
RESET
SUSPEND
COUNTING
RESET
In SUSPEND mode the charge safety timer is put on hold (i.e., charge safety timer is not reset), normal
operation resumes when the timer returns to the normal operating mode (COUNTING). If charge termination is
not reached within the timer period a fault condition is detected. Under those circumstances the LED status is
updated to indicate a fault condition and :
1. bq24060/61/62/64/65/66: charger is turned off and the charge safety timer fault condition is latched.
2. bq24063, TE = LO: charger is turned off and the charge safety timer fault condition is latched.
3. bq24063 TE pin, = HI: charger is not turned OFF, timer fault condition is latched and indicated in STAT1,
STAT2 pins. Charger is turned OFF when TE :HI→LO, and charge current is below termination threshold
I_(TERM).
When the charge safety timer fault latch is set and the charger is turned off a small current IFAULT is applied to
the OUT pin, as long as input power (IN) is detected AND V(OUT) < V_(RCHG), as part of a timer fault recovery
protocol. This current allows the output voltage to rise above the recharge threshold V_(RCHG) if the pack is
removed, and assures that the charge safety timer fault latch is reset if the pack is removed and re-inserted.
Table 8 further details the charge safety timer fault latch operation.
Table 8. Charge Safety Timer Latch Functionality
CHARGE SAFETY TIMER FAULT LATCHED AND
V(OUT) > V_(RCHG)
V(OUT) < V_(RCHG)
CHARGE SAFETY TIMER FAULT LATCH RESET AT
CE rising edge, or OVP detected
Input power removed (not detected)
New charging cycle started; see state diagram
CE rising edge, or OVP detected
Input power removed (not detected)
New charging cycle started; see state diagram
LDO MODE OPERATION
The bq24060/61/62/64/65/66 devices operate as a LDO when the timer pin TMR is left open (floating). The
bq24063 operates as an LDO when TE = HI.
When the LDO mode is set, the termination is disabled, and the charger is ON as long as the charging process
is enabled.
When the LDO mode is set the termination is disabled and an external host can monitor the charge current at
pin ISET, making it possible to continue the battery charging process until the charge current tapers down to a
value lower than the internally set termination threshold (10% of fast charge programmed current).
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