bq24030, bq24031, bq24032,
bq24032A, bq24035, bq24038, bq24039
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SLUS618C–AUGUST 2004–REVISED JUNE 2005
FUNCTIONAL DESCRIPTIONS (continued)
bq24039 Differences
The bq24039 operates differently from other core parts when dealing with PSEL, USB charge levels, and charge
termination levels. Pin 8 is changed fro PSEL to ISET3. However, the PSEL function was tied high internally,
making the input AC adaptor the first choice when present. When AC is present, the PSEL pin is not externally
available to transfer to the USB input (toggle PSEL low).
The ISET3 pin, when set high, can be thought of as a 2x multiplier for the ISET2 current program level (USB
100/500 mA -> 200/1000 mA). The ISET3 also programs the termination level to C/10 when set high and C/25
when set low, for all charging sources.
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 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 defaults to USB charging. If USB input is grounded, then the
bqTINY-III 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(1)
PSEL STATE
AC
USB
CHARGE
SOURCE
MAXIMUM
SYSTEM
POWER
SOURCE
USB BOOT-UP
FEATURE
CHARGE RATE(2)
Present(3)
Absent(4)
Present
Absent
Absent
Present
Present
Absent
Absent
Present
Present
Absent
AC
USB
USB
N/A
AC
ISET2
ISET2
ISET2
N/A
AC
USB
USB
Battery
AC
Enabled
Enabled
Enabled
Disabled
Disabled
Disabled
Disabled
Disabled
Low
Present
Absent
ISET1
ISET2
ISET1
N/A
USB
AC
USB
AC
High
Present
Absent
N/A
Battery
(1) Table 1 is for all ICs with the following exception: For bq24039, the PSEL is tied high internally and ISET3 determines if bootup is
enabled (ISET3 = Low = ENABLED; ISET3 = High = DISABLED).
(2) Battery charge rate is always set by ISET1, but may be reduced by a limited input source (ISET2 USB mode) and IOUT system load.
(3) Present is defined as input being at a higher voltage than the BAT voltage (sources power good is low).
(4) AC Absent is defined as AC input not present (ACPG is High) or Q1 turned off due to overvoltage in bq24035/39.
Boot-Up Sequence
In order to facilitate the system start-up and USB enumeration, the bqTINY-III offers a proprietary boot-up
sequence. On the first application of power to the bqTINY-III, 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 implements CE and ISET2 inputs settings. Table 1 indicates when this feature is enabled.
See Figure 13.
13
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