BQ24030_07 Datasheet, PDF(22/38 Page) Texas Instruments – SINGLE-CHIP CHARGE AND SYSTEM POWER-PATH MANAGEMENT IC (bqTINY)

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BQ24030_07 Datasheet, PDF (22/38 Pages) Texas Instruments – SINGLE-CHIP CHARGE AND SYSTEM POWER-PATH MANAGEMENT IC (bqTINY)

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bq24030, bq24031, bq24032A

bq24035, bq24038

SLUS618F â AUGUST 2004 â REVISED NOVEMBER 2006

www.ti.com

(PRECHG)

V(PRECHG)

RSET

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, RSET, 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.

(OUT)

V(SET) K(SET)

RSET

(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.

The charge level for the bq24032A/38, 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, V(SET), 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.

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 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-series monitors the battery-pack voltage between the BAT and VSS pins. When the

battery voltage rises to the VO(BAT-REG) threshold (4.1-V, 4.2-V, or 4.36-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 (VO(REG)) and charging (battery refresh

threshold, ~100 mV below VO(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 theTimer 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 inputââpriority 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 tSW-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 was dead or missing, the system would lose power

unless the PSEL pin was used to transfer power prior to shutdown.

If this is a concern, there is a simple external solution. Externally toggling the PSEL (bq24030/31/5/8) pin

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