BQ24070_14 Datasheet, PDF(15/33 Page) Texas Instruments

English

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

BQ24070_14 Datasheet, PDF (15/33 Pages) Texas Instruments – System Power-Path Management IC

◁

www.ti.com

bq24070, bq24071

SLUS694G â MARCH 2006 â REVISED DECEMBER 2014

Device Functional Modes (continued)

8.4.2 Standy Mode - V(IN) > VI(BAT)and CE (Chip Enable) Pin = Low

The CE (chip enable) digital input is used to disable or enable the IC. A high-level signal on this pin enables the

chip, and a low-level signal disables the device and initiates the standby mode. The bq2407x enters the low-

power standby mode when the CE input is low with input present. In this suspend mode, internal power FET Q1

(see Figure 3) is turned off; the battery (BAT pin) is used to power the system through Q2 and the OUT pin. This

feature is designed to limit the power drawn from the input supply (such as USB suspend mode).

8.4.3 Battery Charge Mode - V(IN) > VI(BAT), Battery Present, CE pin = High and DPPM Pin Not Floating

8.4.3.1 Automous Power Selection and Boot-Up Sequence

The MODE control pin selects the priority of the input sources. If an input source is not available, the battery is

selected as the source. With the MODE pin high, the bq2407x charges from the input at the charge rate set by

the ISET1 pin. With the MODE pin low, the bq2407x defaults to the USB charging at the charge rate, and the

supply current is limited by the ISET2 pin (100 mA for ISET2 = Low, 500 mA for ISET2 = High). This feature

allows the use of a single connector (mini-USB cable), where the host programs the MODE pin according to the

source that is connected (AC adaptor or USB port). Table 2 summarizes the MODE pin function.

Table 2. Power Source Selection Function Summary

MODE STATE

Low

High

ADAPTER

Present

Absent

Present

Absent

MAXIMUM

CHARGE RATE(1)

ISET2

N/A

ISET1

N/A

SYSTEM

POWER

SOURCE

USB

Battery

USB BOOT-UP

FEATURE

Enabled

Disabled

(1) Battery charge rate is always set by ISET1, but may be reduced by a limited input source (ISET2 USB mode) and IOUT system load.

With Mode= Low, in order to facilitate the system start-up and USB enumeration, the bq2407x offers a

proprietary boot-up sequence. On the first application of power to the bq2407x, this feature enables the 100-mA

USB charge rate for a period of approximately 150 ms, (t(BOOT-UP)), ignoring the ISET2 and CE inputs setting.

At the end of this period, the bq2407x implement CE and ISET2 input settings. See Figure 9.

V(OUT) is regulated to VO(OUT-REG) as long as the the system load, I(SYS), plus the battery charge current, IO(BAT),

set by ISET1 does not exceed the maximum input current of

IIN = 2 A if MODE is high or

IIN set by ISET2 if MODE is low.

If V(OUT) drops to the DPPM pin preset value, V(DPPM) Ã SF, due to a limited amount of input current, then the

battery charging current is dynamically reduced until the output voltage stops dropping. If the system demands

more current than the input can provide, the output voltage drops just below the battery voltage and Q2 turns on

which allows the battery to supplement the input current to the system. The DPPM circuity is explained in detail

in Power-Path Management. The following sections explain the battery charge process in detail. Floating the

DPPM pin disables battery charging.

Product Folder Links: bq24070 bq24071

Submit Documentation Feedback

▷