BQ24030 Datasheet, PDF (14/20 Pages) Texas Instruments – SINGLE-CHIP CHARGE AND SYSTEM POWER-PATH MANAGEMENT IC (bqTINYI)

bq24030, bq24032, bq24035
SLUS618 – AUGUST 2004
www.ti.com
Battery Pre-Conditioning
During a charge cycle if the battery voltage is below the V_(LOWV) threshold, the bqTINY-III applies a precharge
current, I_O(PRECHG), to the battery. This feature revives deeply discharged cells. The resistor connected between
the ISET1 and VSS, R_SET, determines the precharge rate. The V_(PRECHG) and K_(SET)parameters are specified in
the specifications table. Note that this applies to both AC and USB charging.
I_O
(PRECHG)
+
V_(PRECHG)
R_SET
K_(SET)
(3)
The bqTINY-III activates a safety timer, t_(PRECHG), during the conditioning phase. If V_(LOWV) threshold is not
reached within the timer period, the bqTINY-III turns off the charger and enunciates FAULT on the STAT1 and
STAT2 pins. The timeout is extended if the charge current is reduced by DPPM. Please refer to the Timer Fault
Recovery section for additional details.
Battery Charge Current
The bqTINY-III offers on-chip current regulation with programmable set point. The resistor connected between
the ISET1 and VSS, R_SET, determines the charge level. The charge level may be reduced to give the system
priority on input current (see DPPM). The V_(SET) and K_(SET) parameters are specified in the specifications table.
I_O
(OUT)
+
V_(SET) K_(SET)
R_SET
(4)
When powered from a USB port, the input current available (0.1 A/0.5 A) is typically less than the programmed
(ISET1) charging current and therefore the DPPM feature attempts to keep the output from being pulled down by
reducing the charging current.
For the bq24032 the charge level, during AC operation only (PSEL=High), can be changed by a factor of 2 by
setting the ISET2 pin high (full charge) or low (half charge). The voltage on the ISET1 pin, VSET1, is divided by
2 when in the half constant current charge mode. Note that With PSEL low the ISET2 pin controls only the
0.1 A/0.5 A USB current level.
Please also refer to section titled Power Path Management for additional details.
Battery Voltage Regulation
The voltage regulation feedback is through the BAT pin. This input is tied directly to the positive side of the
battery pack. The bqTINY-III monitors the battery-pack voltage between the BAT and VSS pins. When the
battery voltage rises to V_O(REG) threshold, the voltage regulation phase begins and the charging current begins to
taper down.
As a safety backup, the bqTINY-III also monitors the charge time in the charge mode. If charge is not terminated
within this time period, t_(CHG), the bqTINY-III turns off the charger and enunciates FAULT on the STAT1 and
STAT2 pins. Refer to the DPPM operation under Case 1, for information on extending the safety timer during
DPPM operation. Please refer to the Timer Fault Recovery section titled for additional details.
Temperature Regulation and Thermal Protection
In order to maximize charge rate, the bqTINY-III features a junction temperature regulation loop. If the power
dissipation of the IC results in a junction temperature greater than the T_J(REG) threshold, the bqTINY-III throttles
back on the charge current in order to maintain a junction temperature around the T_J(REG) threshold. To avoid
false termination, the taper detect function is disabled while in this mode.
The bqTINY-III also monitors the junction temperature, T_J, of the die and disconnects the OUT pin from AC or
USB inputs if T_J exceeds T_(SHTDWN). This operation continues until T_J falls below T_(SHTDWN) by the hysteresis level
specified in the specification table.
There is no thermal protection for the battery supplement mode. The Q2 FET continues to connect the battery to
the output (system), if input power is not sufficient. However, there is a short circuit protection circuit that limits
the battery discharge current such that the maximum power dissipation of the part is not exceeded, under typical
design conditions
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