BQ24030 Datasheet, PDF (11/20 Pages) Texas Instruments – SINGLE-CHIP CHARGE AND SYSTEM POWER-PATH MANAGEMENT IC (bqTINYI)

bq24030, bq24032, bq24035
www.ti.com
SLUS618 – AUGUST 2004
FUNCTIONAL DESCRIPTIONS (continued)
Autononous Power Source Selection
Note that 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 the 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
PSEL STATE
Low
High
AC
Present ⁽¹⁾
Absent ⁽²⁾
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
CHARGE RATE
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) Present is defined as input being at ahigher voltage than the BAT voltage.
(2) AC Absent is defined as AC input notpresent (sleep mode) or Q1 turned off due to overvoltage inbq24035.
Boot-Up Sequence
In order to facilitate the system startup and USB enumeration, the bqTINY-III offers a proprietarty boot-up
sequence. Upon 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.
Power Path Management
The bqTINY-III 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 priopirty 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).
AC Adapter
AC
VDC
OUT
USB Port
D+
D−
VBUS
GND
GND
Q1
USB
30 mΩ
BAT
Q3
Q2
bq2403x
Figure 4. Power Path Management
PACK+
+
PACK−
System
UDG−04082
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