BQ24071 Datasheet, PDF(14/26 Page) Texas Instruments – SINGLE-CHIP LI-ION CHARGE AND SYSTEM POWER-PATH MANAGEMENT IC

English

English German Russian Spanish Italian Polish Chinese Japanese Korean French Portuguese	Language :

BQ24071 Datasheet, PDF (14/26 Pages) Texas Instruments – SINGLE-CHIP LI-ION CHARGE AND SYSTEM POWER-PATH MANAGEMENT IC

◁

bq24070

bq24071

SLUS694B â MARCH 2006 â REVISED AUGUST 2006

www.ti.com

FUNCTIONAL DESCRIPTIONS (continued)

Dynamic Power-Path Management (DPPM)

The theory of operation is the same as described in CASE 1, except that Q1 is restricted to the USB current

level selected by the ISET2 pin.

Note that the DPPM voltage, V(DPPM), is programmed as follows:

V(DPPMâREG) + I(DPPM) R(DPPM) SF

(2)

where

R(DPPM) is the external resistor connected between the DPPM and VSS pins.

I(DPPM) is the internal current source.

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

Feature Plots

Figure 5 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 5. DPPM and Battery Supplement Modes

Figure 6 illustrates when Mode is toggled low for 500 Âµs. Power transfers from AC to USB to AC; channel 1

Submit Documentation Feedback

▷