bq24030, bq24031, bq24032,
bq24032A, bq24035, bq24038, bq24039
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SLUS618C–AUGUST 2004–REVISED JUNE 2005
0 A to ~2.2 A and back to 0 A as shown in the bottom waveform. As the IOUT load reaches 0.5 A, along with the
1-A charge current, the adaptor starts to current limit, the output voltage drops to the DPPM-OUT threshold of
4.26 V. This is DPPM mode. The AC input tracks the output voltage by the dropout voltage of the AC FET. The
battery charge current is then adjusted back as necessary to keep the output voltage from falling any further.
Once the output load current exceeds the input current, the battery has to supplement the excess current and the
output voltage falls just below the battery voltage by the dropout voltage of the battery FET. This is the battery
supplement mode. When the output load current is reduced, the operation described is reversed as shown. If the
DPPM-OUT voltage was set below the battery voltage, during input current limiting, the output falls directly to the
battery's voltage.
Under USB operation, when the loads exceeds the programmed input current thresholds a similar pattern is
observed. If the output load exceeds the available USB current, the output instantly goes into the battery
supplement mode.
V
AC
V
OUT
V
V
Reg. @ 4.4 V (bq24032)
OUT
= 4.26 V, DPPM Mode
DPPM − OUT
V
OUT
9 V , BAT Supplement Mode
BAT
I
I
CHG
OUT
Figure 5. DPPM and Battery Supplement Modes
Figure 6 illustrates when PSEL is toggled low for 500 µs. Power transfers from AC to USB to AC; 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. When the PSEL went low (1st div), the AC FET opened, and the
output fell until the USB FET turned on. Turning off the active source before turning on the replacement source is
referred to as break-before-make switching. The rate of discharge on the output is a function of system
capacitance and load. Note the cable IR drop in the AC and USB inputs when they are under load. At the 4th
division, the output has reached steady-state operation at the DPPM voltage level (charge current has been
reduced due to the limited USB input current). At the 6th division, the PSEL goes high and the USB FET turns off
followed by the AC FET turning on. The output returns to its regulated value, and the battery returns to its
programmed current level.
16
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