TEXAS INSTRUMENTS bq2054 Technical data

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bq2054

Lithium Ion Fast-Charge IC

Features

Safe charge of Lithium Ion bat

➤

tery packs

Voltage-regulated current-

➤

limited charging

Fast charge terminated by se

➤

lectable minimum current; safety backup termination on maximum time

Charging continuously qualified

➤

by temperature and voltage lim its

Pulse-width modulation control

➤

ideal for high-efficiency switchmode power conversion

➤ Direct LED control outputs dis-

play charge status and fault conditions

Pin Connections

ICTL

BAT

VCOMP

ICOMP

TERM

SNS

16-Pin Narrow

DIP or SOIC

PN205401.eps

LED2/DSEL

LED

MOD

LCOM

LED

TPWM

General Description

The bq2054 Lithium Ion Fast-

Charge IC is designed to optimize

charging of lithium ion (Li-Ion) chemistry batteries. A flexible pulse-width modulation regulator allows the bq2054 to control voltage

and current during charging. The

regulator frequency is set by an ex ternal capacitor for design flexibility. The switch-mode design keeps power dissipation to a minimum.

The bq2054 measures battery tem

perature using an external thermis tor for charge qualification. Charging begins when power is applied or on battery insertion.

For safety, the bq2054 inhibits charging until the battery voltage and temperature are within con-

Pin Names

TM Time-out programming

ICTL

BAT Battery voltage input

VCOMP Voltage loop comp input

ICOMP Current loop comp input

TERM

SNS Sense resistor input

TS Temperature sense input

input

Inrush current control output

Minimum current termination select input

figured limits. If the battery voltage is less than the low-voltage thresh old, the bq2054 provides low-current conditioning of the battery.

A constant current-charging phase re plenishes up to 70% of the charge ca pacity, and a voltage-regulated phase returns the battery to full. The charge cycle terminates when the charging

current falls below a user-selectable current limit. For safety, charging ter minates after maximum time and is suspended if the temperature is out side the preconfigured limits.

The bq2054 provides status indica tions of all charger states and faults for accurate determination of the battery and charge system condi tions.

TPWM Regulator timebase input

LED

Charge status output 3

LCOM Common LED output

System ground

5.0V±10% power

MOD Modulation control output

LED

Charge status output 1

/ Charge status output 2/

DSEL Display select input

6/99 H

bq2054

Pin Descriptions

TM Time-out programming input

This input sets the maximum charge time. The resistor and capacitor values are deter mined using Equation 5. Figure 7 shows the resistor/capacitor connection.

ICTL

BAT Battery voltage input

VCOMP Voltage loop compensation input

TERM

ICOMP Current loop compensation input

SNS Charging current sense input

Inrush current control output

is driven low during the fault or

ICTL charge-complete states of the chip. It is used to disconnect the capacitor across the battery pack terminals, preventing inrush currents from tripping overcurrent protection fea tures in the pack when a new battery is in serted.

BAT is the battery voltage sense input. This potential is generally developed using a high-impedance resistor divider network connected between the positive and the negative terminals of the battery. See Figure 4 and Equation 1.

This input uses an external R-C network for voltage loop stability.

Minimum current termination select

This three-state input is used to set I fast charge termination. See Table 2.

This input uses an external R-C network for current loop stability.

Battery current is sensed via the voltage de veloped on this pin by an external sense re sistor, R

, connected in series with the

SNS

negative terminal of the battery pack. See Equation 6.

MIN

TS Temperature sense input

This input is used to monitor battery tempera ture. An external resistor divider network sets the lower and upper temperature thresholds.

See Figure 6 and Equations 3 and 4.

TPWM Regulation timebase input

This input uses an external timing capacitor to ground to set the pulse-width modulation (PWM) frequency. See Equation 7.

LCOM Common LED output

Common output for LED in a high-impedance state during initiali zation to read programming input on DSEL.

MOD Current-switching control output

MOD is a pulse-width modulated push/pull output that is used to control the charging current to the battery. MOD switches high to enable current flow and low to inhibit current flow.

LED

–

Charger display status 1–3 outputs

LED

These charger status output drivers are for the direct drive of the LED display. Display modes are shown in Table 1. These outputs are tri-stated during initialization so that DSEL can be read.

for

DSEL Display select input

This three-level input controls the LED charge display modes. See Table 1.

VCCsupply

5.0V,±10% power

Ground

. This output is

1–3

bq2054

Charge Algorithm

The bq2054 uses a two-phase fast charge algorithm. In phase 1, the bq2054 regulates constant current (I I

) until V

MAX

bq2054 then transitions to phase 2 and regulates con stant voltage (V falls below the programmed I ing current must remain below I ore a valid fast charge termination is detected. Fast charge then terminates, and the bq2054 enters the Charge Complete state. See Figures 1 and 2.

(= V

CELL

CELL=VREG

BAT-VSNS

) rises to V

) until the charging current

threshold. The charg

MIN

for 120±40ms bef

MIN

REG

SNS

. The

Charge Qualification

The bq2054 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 pre-charge qualifi cation and temperature monitoring. The bq2054 first checks that the battery temperature is within the al lowed, user-configurable range. If the temperature is out of range, the bq2054 enters the Charge Pending state and waits until the battery temperature is within the allowed range. Charge Pending is enunciated by LED flashing.

MAX

Thermal monitoring continues throughout the charge cycle, and the bq2054 enters the Charge Pending state when the temperature out of range. (There is one excep tion; if the bq2054 is in the Fault state—see below—the

out-of-range temperature is not recognized until the bq2054 leaves the Fault state.) All timers are sus

pended (but not reset) while the bq2054 is in Charge

Pending. When the temperature comes back into range,

the bq2054 returns to the point in the charge cycle

where the out-of-range temperature was detected.

When the temperature is valid, the bq2054 then regu lates current to I period t transient voltage spikes that may occur when charge current is first applied), the chip begins monitoring V

CELL

expiration of time-out limit t

short), the bq2054 enters the Fault state. If V achieved before expiration of the time limit, the chip be

gins fast charging.

Once in the Fault state, the bq2054 waits until V cycled or a new battery insertion is detected. It then starts a new charge cycle and begins the qualification

process again.

(which prevents the chip from reacting to

.IfV

CELL

(=I

COND

does not rise to at least V

/5). After an initial holdoff

MAX

(e.g. the cell has failed

MTO

MIN

Voltage

before the

MIN

REG

COND

MIN

Current

Qualification

Figure 1. bq2054 Charge Algorithm

Fast Charge

Phase 1 Phase 2

Current

Time

GR205401.eps

MIN

Voltage

bq2054

BAT

Charge

VCC 4.5V

< V

LCO

Qualification Test

BAT

PASS: V

Fast

< V

BAT

REG

Chip On

Present

BAT

< V

BAT

< V

MIN

REG

HCO

Current

Regulation

@ I

COND

Phase 1 I = I

MAX

Temperature

in Range

t t > t

BAT

Temperature

Checks On

Battery

Status?

Fail: t = tQT or

< V

BAT

> V

< V

> V

MTO

LCO

HCO

LCO

HCO

Temperature Out

of Range or

Thermistor Absent

LED3 =1

Absent

< V

BAT

BAT > VHCO

Fault

MOD = 0

LCO

Charge

Pending

LED3 flash

MOD = 0

BAT

LCO

HCO

SNS

> I

BAT

MIN

SNS

t t

LCO

HCO

MTO

MIN

Phase 2

V = V

REG

Charge

Complete

BAT

< V

> V

LCO

HCO

Figure 2. bq2054 State Diagram

Temperature Out

of Range or

Thermistor Absent

Temperature In

Range, Return

to Original State

FG205401.eps

bq2054

Charge Status Display

Charge status is enunciated by the LED driver outputs LED

–LED3. Three display modes are available in the

bq2054; the user selects a display mode by configuring pin DSEL. Table 1 shows the three display modes.

The bq2054 does not distinguish between an overvoltage fault and a “battery absent” condition. The bq2054 enters the Fault state, enunciated by turning on LED

, whenever the battery is absent. The bq2054,

therefore, gives an indication that the charger is on even when no battery is in place to be charged.

Configuring the Display Mode and I

DSEL/LED is an LED driver pin as an output and a programming pin as an input. The selection of pull-up, pull-down, or no pull resistor programs the display mode on DSEL per Table 1. The bq2054 latches the programming data sensed on the DSEL input when any one of the following three events occurs:

1. V

2. The bq2054 leaves the Fault state.

rises to a valid level.

3. The bq2054 detects battery insertion.

The LEDs go blank for approximately 750ms (typical) while new programming data is latched.

Table 1. bq2054 Display Output Summary

Mode Charge Action State LED

Battery absent or over-voltage fault Low Low High

Pre-charge qualification Flash Low Low

DSEL = 0

(Mode 1)

Charge pending (temperature out of range) X X Flash

Battery absent or over-voltage fault Low Low High

DSEL = 1

(Mode 2)

Charge pending (temperature out of range) X X Flash

Battery absent or over-voltage fault Low Low High

Fast charge: current regulation Low High Low

DSEL = Float

(Mode 3)

Fast charge: voltage regulation High High Low

Charge pending (temperature out of range) X X Flash

Note: 1 = VCC; 0 = VSS; X = LED state when fault occurred; Flash =

Fast charging High Low Low

Charge complete Low High Low

Charging fault X X High

Pre-charge qualification High High Low

Fast charge Low High Low

Charge complete High Low Low

Charging fault X X High

Pre-charge qualification Flash Flash Low

Charge complete High Low Low

Charging fault X X High

MIN

is a bi-directional pin with two functions; it

sec. low,

sec high.

LED

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