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SLUS549C − DECEMBER 2002 − REVISED AUGUST 2004
FUNCTIONAL DESCRIPTION
BATTERY CHARGE CURRENT
The bqTINY-II offers on-chip current regulation with programmable set point. The resistor connected between the
ISET1 and V , R
, determines the AC charge rate. The V
and K
parameters are specified in the
SS
SET
(SET)
(SET)
specifications table.
V
K
(SET)
(SET)
I
+
O (OUT)
R
SET
(2)
When charging from a USB port, the host controller has the option of selecting either 100 mA or 500 mA charge rate
using ISET2 pin. A low-level signal sets current at 100 mA and a high level signal sets current at 500 mA. A high-Z
input disables USB charging
BATTERY VOLTAGE REGULATION
The voltage regulation feedback is through the OUT pin. This input is tied directly to the positive side of the battery
pack. The bqTINY-II monitors the battery−pack voltage between the OUT and VSS pins. When the battery voltage
rises to V
threshold, the voltage regulation phase begins and the charging current begins to taper down.
O(REG)
As a safety backup, the bqTINY-II also monitors the charge time in the charge mode. If charge is not terminated within
this time period, t , the bqTINY-II turns off the charger and enunciates FAULT on the STATx pins. Please refer
(CHG)
to the TIMER FAULT RECOVERY section for additional details.
CHARGE TAPER DETECTION, TERMINATION AND RECHARGE
The bqTINY-II monitors the charging current during the voltage regulation phase. Once the taper threshold, I
,
(TAPER)
is detected the bqTINY-II initiates the taper timer, t
. Charge is terminated after the timer expires. The resistor
(TAPER)
connected between the ISET1 and V , R
, determines the taper detection level. The V
and K
SS
SET
(TAPER)
(SET)
parameters are specified in the specifications table. Note that this applies to both AC and USB charging.
V
K
(SET)
(TAPER)
I
+
(TAPER)
R
SET
(3)
The bqTINY-II 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-II 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
(TERM)
a fully charged battery. Note that charge timer and taper timer are bypassed for this feature. The resistor connected
between the ISET1 and V , R
, determines the taper detection level. The V
and K
parameters are
SS SET
(TERM)
(SET)
specified in the specifications table. Note that this applies to both AC and USB charging.
V
K
(TERM)
(SET)
I
+
(TERM)
R
SET
(4)
After charge termination, the bqTINY-II re-starts the charge once the voltage on the OUT pin falls below the V
threshold. This feature keeps the battery at full capacity at all times.
(RCH)
NOTE ON bq24026
The bq24026 monitors the charging current during the voltage regulation phase. Once the taper threshold, I
,
(TAPER)
is detected the bq24026 terminates the charge. There is no taper timer, t
for this version.
(TAPER)
The resistor connected between the ISET1 and V , R
charge, taper level is fixed at 10% of the 100- or 500-mA charge rate.
, determines the taper detection level for AC input. For USB
SS SET
Also note that there is I detection in bq24026.
(TERM)
13
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