BQ24030-Q1 Datasheet, PDF (16/34 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
Figure 7 illustrates when AC is removed, power transfers to USB [PSEL = H (AC primary source), channel 1
(CH1) VAC = 5.4 V, channel 2 (CH2) V_(USB) = 5 V, channel 3 (CH3) V_OUT, output current I_OUT = 0.25 A, channel 4
(CH4) V_BAT = 3.5 V, and I_(PGM-CHG) = 1 A]. The power transfer from AC to USB only takes place after the primary
source (AC) is considered bad (too low, V_AC ≤ V_BAT + 125 mV) indicated by the ACPG FET turning off (open
drain not shown). Thus, the output drops down to the battery voltage before the USB source is connected (sixth
division). The output starts to recover when the USB FET starts to limit the input current (seventh division) and
the output drops to the V_(DPPM-REG) threshold.
USB Input Current Limit Is Reached
DPPM Mode
V_USB
V_OUT
V_AC
V_BAT
AC Declared Not Present, USB Power Applied
Figure 7. Remove AC – Power Transfer to USB
Figure 8 illustrates when AC (low battery) is removed, power transfers to USB [PSEL = H, channel 1 (CH1)
VAC = 5.4 V, channel 2 (CH2) V_(USB) = 5 V, channel 3 (CH3) V_OUT, output current I_OUT = 0.25 A, channel 4 (CH4)
V_BAT = 2.25 V, and I_(PGM-CHG) = 1 A]. This figure is the same as when the battery has more capacity. Note that
the output drops to the battery voltage before switching to USB power. A resistor divider between AC and ground
tied to PSEL can toggle the power transfer earlier, if necessary.
V_USB
V_OUT
DPPM Mode
V_AC
V_BAT
Figure 8. Remove AC (Low Battery) – Power Transfer to USB
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