BQ24030_07 Datasheet, PDF (13/38 Pages) Texas Instruments – SINGLE-CHIP CHARGE AND SYSTEM POWER-PATH MANAGEMENT IC (bqTINY)

bq24030, bq24031, bq24032A
bq24035, bq24038
www.ti.com
SLUS618F – AUGUST 2004 – REVISED NOVEMBER 2006
FUNCTIONAL DESCRIPTIONS (continued)
bq24038 Differences
The bq24038 replaces USBPG with pin VBSEL, to enable user selection of the charge voltage. In addition, pin
ACPG was modified to PG. PG is active low when either AC power or USB power is detected.
Autonomous Power Source Selection, PSEL Control Pin
The PSEL pin selects the priority of the input sources (high = AC, low = USB), if that primary source is not
available (based on ACPG, USBPG signal), then it uses the secondary source. If neither input source is
available, then the battery is selected as the source. With the PSEL input high, the bqTINY III-series attempts to
charge from the AC input. If AC input is not present, the USB is selected. If both inputs are available, the AC
adapter has priority. With the PSEL input low, the bqTINY III-series defaults to USB charging. If USB input is
grounded, then the bqTINY III-series charges from the AC input at the USB charge rate (as selected by ISET2).
This feature can be used in system where AC and USB power source selection is done elsewhere. The PSEL
function is summarized in Table 1.
Table 1. Power Source Selection Function Summary
PSEL STATE
Low
High
AC
Present ⁽²⁾
Absent ⁽³⁾
Present
Absent
Present
Absent
Present
Absent
USB
Absent
Present
Present
Absent
Absent
Present
Present
Absent
CHARGE
SOURCE
AC
USB
USB
N/A
AC
USB
AC
N/A
MAXIMUM
CHARGE RATE⁽¹⁾
ISET2
ISET2
ISET2
N/A
ISET1
ISET2
ISET1
N/A
SYSTEM
POWER
SOURCE
AC
USB
USB
Battery
AC
USB
AC
Battery
USB BOOT-UP
FEATURE
Enabled
Enabled
Enabled
Disabled
Disabled
Disabled
Disabled
Disabled
(1) Battery charge rate is always set by ISET1, but may be reduced by a limited input source (ISET2 USB mode) and I_OUT system load.
(2) Present is defined as input being at a higher voltage than the BAT voltage (sources power good is low).
(3) AC Absent is defined as AC input not present (ACPG is High) or Q1 turned off due to overvoltage in bq24035.
Boot-Up Sequence
In order to facilitate the system start-up and USB enumeration, the bqTINY III-series offers a proprietary boot-up
sequence. On the first application of power to the bqTINY III-series, this feature enables the 100-mA USB
charge rate for a period of approximately 150 ms, (t_(BOOT-UP)), ignoring the ISET2 and CE inputs setting. At the
end of this period, the bqTINY III-series implements CE and ISET2 inputs settings. Table 1 indicates when this
feature is enabled. See Figure 13.
Power-Path Management
The bqTINY III-series powers the system while independently charging the battery. This features reduces the
charge and discharge cycles on the battery, allows for proper charge termination, and allows the system to run
with an absent or defective battery pack. This feature gives the system priority on input power, allowing the
system to power up with a deeply discharged battery pack. This feature works as follows (note that PSEL is
assumed HIGH for this discussion).
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