BQ2954_13 Datasheet, PDF(3/23 Page) Texas Instruments

English

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

BQ2954_13 Datasheet, PDF (3/23 Pages) Texas Instruments – Lithium Ion Charge Management IC

◁

bq2954

VSS

VCOMP

BAT

SNS

VCC

ITERM

TPWM

Power-On

Reset

MTO

Timer

Voltage

Reference

Oscillator

DSEL

CSEL

Charge

Control

State

Machine

Display

Control

PWM

Regulator

LED1

LED2

BTST

CHG

LCOM

MOD

ICOMP

BD2954.eps

Figure 1. Functional Block Diagram

Functional Description

The bq2954 functional operation is described in terms of

the following (Figure 1):

I Charge algorithm

I Charge qualification

I Charge status display

I Configuring the display and termination

I Voltage and current monitoring

I Battery insertion and removal

I Temperature monitoring

I Maximum time--out

I Charge regulation

I Recharge after fast charge

Charge Algorithm

The bq2954 uses a two-phase fast-charge algorithm. In

phase 1, the bq2954 regulates constant current until the

voltage on the BAT pin, VBAT, rises to the internal

threshold, VREG. The bq2954 then transitions to phase 2

and regulates constant voltage (VBAT = VREG) until the

charging current falls below the programmed IMIN

threshold. Fast charge then terminates, and the bq2954

enters the Charge Complete state. (See Figure 2.)

Charge Qualification

The bq2954 starts a charge cycle when power is applied

while a battery is present or when a battery is inserted.

Figure 2 shows the state diagram for the bq2954. The

bq2954 first checks that the battery temperature is

within the allowed, user-configurable range. If the tem-

perature is out of range, the bq2954 remains in the

QUALIFICATION state (S01) and waits until the battery

temperature and voltage are within the allowed range.

If during any state of charge, a temperature excursion

occurs HOT, the bq2954 proceeds to the DONE state

(S04) and indicates this state on the LED outputs and

provides no current. If this occurs, the bq2954 remains

in the DONE state unless the following two conditions

are met:

I Temperature falls within valid charge range

I VBAT falls below the internal threshold,VRCHG

If these two conditions are met, a new charge cycle be-

gins. During any state of charge, if a temperature ex-

cursion occurs COLD, the bq2954 terminates charge and

returns to the QUALIFICATION state (S01). Charge re-

starts if VBAT and temperature are in valid range.

When the temperature and voltage are valid, the bq2954

enters the CONDITIONING state (S02) and regulates

current to ICOND (=IMAX/10). After an initial holdoff pe-

riod tHO (which prevents the IC from reacting to tran-

sient voltage spikes that may occur when charge current

is first applied), the IC begins monitoring VBAT. If VBAT

does not rise to at least VMIN before the expiration of

▷