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SLUS530D − SEPTEMBER 2002 − REVISED SEPTEMBER 2003
FUNCTIONAL DESCRIPTION
BATTERY PRE-CONDITIONING
During a charge cycle if the battery voltage is below the V
threshold, the bqTINY applies a precharge current,
(LOWV)
I
, to the battery. This feature revives deeply discharged cells. The resistor connected between the ISET
O(PRECHG)
and V , R
, determines the precharge rate. The V
and K
parameters are specified in the
SS
SET
(PRECHG)
(SET)
specifications table.
V
K
(SET)
(PRECHG)
I
+
O (PRECHG)
R
SET
(3)
threshold is not reached
The bqTINY activates a safety timer, t
, during the conditioning phase. If V
(LOWV)
(PRECHG)
within the timer period, the bqTINY turns off the charger and enunciates FAULT on the STAT1 and STAT2 pins. Refer
to Timer Fault Recovery section for additional details.
BATTERY CHARGE CURRENT
The bqTINY offers on-chip current regulation with programmable set point. The resistor connected between the ISET
and V , R
table.
, determines the charge rate. The V
and K
parameters are specified in the specifications
SS SET
(SET)
(SET)
V
K
(SET)
(SET)
I
+
O (OUT)
R
SET
(4)
BATTERY VOLTAGE REGULATION
Voltage regulation feedback is accomplished through the BAT pin. This input is tied directly and close to the positive
side of the battery pack. The bqTINY monitors the battery-pack voltage between the BAT and VSS pins. When the
battery voltage rises to V
taper down.
threshold, the voltage regulation phase begins and the charging current begins to
O(REG)
As a safety backup, the bqTINY also monitors the charge time in the charge mode. If termination does not occur within
this time period, t , the bqTINY turns off the charger and enunciates FAULT on the STAT1 and STAT1 pins. Refer
(CHG)
to the Timer Fault Recovery section for additional details.
CHARGE TAPER DETECTION, TERMINATION AND RECHARGE
The bqTINY monitors the charging current during the voltage regulation phase. Once the taper threshold, I
,
(TAPER)
is detected the bqTINY initiates the taper timer, t
. Charge is terminated after the timer expires. The resistor
(TAPER)
connected between the ISET and V , R
, determines the taper detection level. The V
and K
SS
SET
(TAPER)
(SET)
parameters are specified in the specifications table.
V
K
(SET)
(TAPER)
I
+
(TAPER)
R
SET
(5)
The bqTINY resets the taper timer in the event that the charge current returns above the taper threshold, I
.
(TAPER)
In addition to the taper current detection, the bqTINY terminates charge in the event that the charge current falls below
the I threshold. This feature allows for quick recognition of a battery removal condition or insertion of a fully
(TERM)
charged battery. Note that taper timer is not used for I
detection. The resistor connected between the ISET
(TERM)
and V , R
, determines the taper detection level. The V
and K
parameters are specified in the
SS
SET
(TERM)
(SET)
specifications table.
V
K
(TERM)
(SET)
I
+
(TERM)
R
SET
(6)
12
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