Datasheet

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BATTERY CHARGE CURRENT
I
O(OUT)
+
ǒ
K
(SET)
V
(SET)
Ǔ
R
SET
(2)
BATTERY VOLTAGE REGULATION
CHARGE TAPER DETECTION, TERMINATION AND RECHARGE
I
(TAPER)
+
V
(TAPER)
K
(SET)
R
SET
(3)
I
(TERM)
+
V
(TERM)
K
(SET)
R
SET
(4)
Note ON bq24026 AND bq24027
SLEEP MODE
bq24020 , , bq24022 , , bq24023
bq24024 , bq24025 , bq24026
bq24027
SLUS549E – DECEMBER 2002 – REVISED NOVEMBER 2007
The bqTINY-II offers on-chip current regulation with a programmable set point. The resistor connected between
the ISET1 and V
SS
, R
SET
, determines the AC charge rate. The V
(SET)
and K
(SET)
parameters are specified in the
specifications table.
When charging from a USB port, the host controller has the option of selecting either a 100-mA or a 500-mA
charge rate using the ISET2 pin. A low-level signal sets the current at 100 mA, and a high-level signal sets the
current at 500 mA. A high-Z input disables USB charging
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 the V
O(REG)
threshold, the voltage-regulation phase begins and the charging current begins to
taper down.
As a safety backup, the bqTINY-II also monitors the charge time. If the charge is not terminated within the time
period specified by t
(CHG)
, the bqTINY-II turns off the charger and asserts a FAULT code on the STATx pins.
Please refer to the TIMER FAULT RECOVERY section for additional details.
The bqTINY-II monitors the charging current during the voltage-regulation phase. When the taper threshold,
I
(TAPER)
, is detected, the bqTINY-II initiates the taper timer, t
(TAPER)
. Charge is terminated after the timer expires.
The resistor connected between the ISET1 and V
SS
, R
SET
, determines the taper detection level. The V
(TAPER)
and
K
(SET)
parameters are specified in the specifications table. Note that this applies to both AC and USB charging.
The bqTINY-II resets the taper timer if the charge current rises above the taper threshold, I
(TAPER)
.
In addition to taper-current detection, the bqTINY-II terminates charge if the charge current falls below the I
(TERM)
threshold. This feature allows quick recognition of a battery-removal condition, or insertion of a fully charged
battery. Note that the charge timer and taper timer are bypassed for this feature. The resistor connected between
the ISET1 and V
SS
, R
SET
, determines the taper detection level. The V
(TERM)
and K
(SET)
parameters are specified in
the specifications table. Note that this applies to both AC and USB charging.
After charge termination, the bqTINY-II re-starts the charge when the voltage on the OUT pin falls below the
V
(RCH)
threshold. This feature keeps the battery at full capacity at all times.
The bq24026 and bq24027 monitor the charging current during the voltage-regulation phase. Once the taper
threshold, I
(TAPER)
, is detected, the bq24026/27 terminates the charge. There is no taper timer (t
(TAPER)
) for this
version.
The resistor connected between the ISET1 and V
SS
, R
SET
, determines the taper-detect level for AC input. For
USB charge, taper level is fixed at 10% of the 100- or 500-mA charge rate.
Also note that there is I
(TERM)
detection in the bq24026 and the bq24027.
The bqTINY-II enters low-power sleep mode if both AC and USB are removed from the circuit. This feature
prevents draining the battery in the absence of input supply.
Copyright © 2002 – 2007, Texas Instruments Incorporated Submit Documentation Feedback 13
Product Folder Link(s): bq24020 bq24022 bq24023 bq24024 bq24025 bq24026 bq24027