bq24030, bq24031, bq24032,
bq24032A, bq24035, bq24038, bq24039
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SLUS618C–AUGUST 2004–REVISED JUNE 2005
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) VOUT; output current, IOUT = 0.25 A; channel 4 (CH4)
VBAT = 2.25 V; and I(PGM-CHG) = 1 A. This figure is the same as where 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
V
USB
OUT
DPPM Mode
V
AC
V
BAT
Figure 8. Remove AC (Low Battery) – PWR XFER to USB
Figure 9 illustrates when AC is applied, power transfers from USB to AC; PSEL = H; channel 1 (CH1) VAC = 5.4
V; channel 2 (CH2) V(USB) = 5 V; channel 3 (CH3) VOUT; output current, IOUT = 0.25 A; channel 4 (CH4) VBAT
=
3.5 V; and I(PGM-CHG) = 1 A. The charger is set for AC priority but is running off USB until AC is applied. When AC
is applied (1st div) and the USB FET opens (2nd div), the AC FET closes (3rd div) and the output recovers from
the DPPM threshold (8th div).
V
AC
V
USB
V
V
OUT
BAT
Break Before Make
V
OUT
Returns to Regulation (4.4 V, bq24032)
Charging Current Returns to I
pgm
DPPM Mode
Figure 9. Apply AC – PWR XFER From USB to AC
Figure 10 illustrates when USB is removed, power transfers from USB to AC; PSEL = L; channel 1 (CH1) VAC =
18
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