BQ24070RHLRG4 Datasheet, PDF(14/31 Page) Texas Instruments – SINGLE-CHIP LI-ION CHARGE AND SYSTEM POWER-PATH MANAGEMENT IC

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BQ24070RHLRG4 Datasheet, PDF (14/31 Pages) Texas Instruments – SINGLE-CHIP LI-ION CHARGE AND SYSTEM POWER-PATH MANAGEMENT IC

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bq24070

bq24071

SLUS694F â MARCH 2006 â REVISED DECEMBER 2009

www.ti.com

SF is the scale factor as specified in the specification table.

Feature Plots

Figure 6 illustrates DPPM and battery supplement modes as the output current (IOUT) is increased; channel 1

(CH1) VAC = 5.4 V; channel 2 (CH2) VOUT; channel 3 (CH3) IOUT = 0 to 2.2 A to 0 A; channel 4 (CH4) VBAT = 3.5

V; I(PGM-CHG) = 1 A. In typical operation, bq24070/1 (VOUT = 4.4 Vreg), 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 Ã V(DPPM-SET) = 4.26 V, VBAT = 3.5 V, Mode = 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 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.

VAC

VOUT

VOUT Reg. @ 4.4 V (bq24070)

VDPPM â OUT = 4.26 V, DPPM Mode

, VOUT â VOUT BAT Supplement Mode

ICHG

IOUT

Figure 6. DPPM and Battery Supplement Modes

Figure 7 illustrates when Mode is toggled low for 500 Î¼s. 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 Mode 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 Mode 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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