BQ24030_07 Datasheet, PDF (16/38 Pages) Texas Instruments – SINGLE-CHIP CHARGE AND SYSTEM POWER-PATH MANAGEMENT IC (bqTINY)

bq24030, bq24031, bq24032A
bq24035, bq24038
SLUS618F – AUGUST 2004 – REVISED NOVEMBER 2006
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(CH1) VAC = 5.4 V; channel 2 (CH2) V_OUT; channel 3 (CH3) I_OUT = 0 to 2.2 A to 0 A; channel 4 (CH4) V_BAT =
3.5 V; I_(PGM-CHG) = 1 A. In typical operation, bq24032A (V_OUT = 4.4 V_reg), through an AC adaptor overload
condition and recovery. The AC input is set for ~5.1 V (1.5 A current limit), I_(CHG) = 1 A, V_(DPPM-SET) = 3.7 V,
V_(DPPM-OUT) = 1.15 × V_(DPPM-SET) = 4.26 V, V_BAT = 3.5 V, PSEL = H, and USB input is not connected. The output
load is increased from 0 A to ~2.2 A and back to 0 A as shown in the bottom waveform. As the I_OUT 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 V_(DPPM-REG) 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_OUT Reg. @ 4.4 V (bq24032A)
V_{DPPM − OUT} = 4.26 V, DPPM Mode
V_OUT ≈ V_BAT, BAT Supplement Mode
I_CHG
I_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) V_OUT; output current, I_OUT = 0.25 A; channel
4 (CH4) V_BAT = 3.5 V; and I_(PGM-CHG) = 1 A. When the PSEL went low (1^st 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 4^th
division, the output has reached steady-state operation at V_(DPPM-REG) (charge current has been reduced due to
the limited USB input current). At the 6^th 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.
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