BQ24030-Q1 Datasheet, PDF (20/34 Pages) Texas Instruments – SINGLE-CHIP CHARGE AND SYSTEM POWER-PATH MANAGEMENT IC

bq24030-Q1
bq24031-Q1
SLUS793B – APRIL 2008 – REVISED OCTOBER 2009.................................................................................................................................................... www.ti.com
Battery Pre-Conditioning
During a charge cycle, if the battery voltage is below the V_(LOWV) threshold (3.0 V, typical), the bqTINY III series
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)
(4)
The bqTINY III series activates a safety timer, t_(PRECHG), during the conditioning phase. If V_(LOWV) threshold is not
reached within the timer period, the bqTINY III series 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. See the Timer Fault
Recovery section for additional details.
Battery Charge Current
The bqTINY III series 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
(BAT)
+
V_(SET) K_(SET)
R_SET
(5)
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.
With ISET2 low the V_(TMR) voltage remains at 2.5 V under normal operating conditions. In this case, the charge
rate is half the programmed current but the safety timer remains t_(CHG). If the bqTINY III series enters DPPM or
thermal regulation mode from this state, the safety timer immediately doubles and then the safety time is
adjusted (inversely proportionate) with the charge current.
See the Power-Path Management section 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 series monitors the battery-pack voltage between the BAT and VSS pins. When the
battery voltage rises to the V_O(BAT-REG) threshold (4.1-V or 4.2-V versions), the voltage regulation phase begins
and the charging current begins to taper down.
If the battery is absent, the BAT pin cycles between charge done (V_O(REG)) and charging (battery refresh
threshold, ~100 mV below V_O(REG)) (see Figure 11).
See Figure 12 for power up by battery insertion.
As a safety backup, the bqTINY III series also monitors the charge time in the charge mode. If charge is not
terminated within this time period, t_(CHG), the bqTINY III series turns off the charger and enunciates FAULT on the
STAT1 and STAT2 pins. See the DPPM operation under Case 1 for information on extending the safety timer
during DPPM operation. See the Timer Fault Recovery section for additional details.
Power Handoff
The design goal of the bqTINY III series is to keep the system powered at all times (OUT pin); first, by either AC
or USB input (priority chosen by PSEL) and lastly by the battery. The input power source is only considered
present if its power-good status is low. There is a break-before-make switching action when switching between
AC to USB or USB to AC, for t_SW-AC/USB, where the system capacitance should hold up the system voltage. Note
that the transfer of power occurs when the sources power-good pin goes high (open-drain output high = power
not present), which is when the input source drops to the battery's voltage. If the battery is below a useable
voltage, the system may reset. Typically, prior to losing the input power, the battery would have some useable
capacity, and a system reset would be avoided. If the battery is dead or missing, the system loses power unless
the PSEL pin is used to transfer power prior to shutdown.
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