Datasheet

T
=4.26V, DPPMMode
Reg.@4.4V(bq24032A)
V
OUT
V
AC
I
CHG
I
OUT
V
OUT
V
DPPM − OU
V
OUT
V
BAT
,BATSupplementMode
≈
bq24030, bq24031
bq24032A, bq24035, bq24038
SLUS618H –AUGUST 2004–REVISED OCTOBER 2009............................................................................................................................................... www.ti.com
(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.
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.
16 Submit Documentation Feedback Copyright © 2004–2009, Texas Instruments Incorporated
Product Folder Link(s): bq24030, bq24031 bq24032A, bq24035, bq24038