Texas Instruments BQ2054SNTR, BQ2054SN, BQ2054PN Datasheet

Features

➤

Safe charge of Lithium Ion bat

tery packs

➤

Voltage-regulated currentlimited 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

General Description

The bq2054 Lithium Ion FastCharge 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-

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.

Lithium Ion Fast-Charge IC

bq2054

TM Time-out programming

input

ICTL

Inrush current control output

BAT Battery voltage input

VCOMP Voltage loop comp input

ICOMP Current loop comp input

TERM

Minimum current termination select input

SNS Sense resistor input

TS Temperature sense input

PN205401.eps

16-Pin Narrow

DIP or SOIC

LED2/DSEL

LED

MOD

LCOM

LED

TPWM

ICTL

BAT

VCOMP

ICOMP

TERM

SNS

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

LED

/ Charge status output 2/

DSEL Display select input

Pin Connections

Pin Names

6/99 H

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

Inrush current control output

ICTL

is driven low during the fault or 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 Battery voltage input

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.

VCOMP Voltage loop compensation input

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

TERM

Minimum current termination select

This three-state input is used to set I

MIN

for

fast charge termination. See Table 2.

ICOMP Current loop compensation input

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

SNS Charging current sense input

Battery current is sensed via the voltage de

veloped on this pin by an external sense re

sistor, R

SNS

, connected in series with the negative terminal of the battery pack. See Equation 6.

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

1–3

. This output is

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

–

LED

Charger display status 1–3 outputs

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.

DSEL Display select input

This three-level input controls the LED

1–3

charge display modes. See Table 1.

VCCsupply

5.0V,±10% power

Ground

bq2054

Charge Algorithm

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

SNS

MAX

) until V

CELL

(= V

BAT-VSNS

) rises to V

REG

. The

bq2054 then transitions to phase 2 and regulates con

stant voltage (V

CELL=VREG

) until the charging current

falls below the programmed I

MIN

threshold. The charg

ing current must remain below I

MIN

for 120±40ms bef

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.

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.

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

COND

(=I

MAX

/5). After an initial holdoff

period t

(which prevents the chip from reacting to transient voltage spikes that may occur when charge current is first applied), the chip begins monitoring V

CELL

.IfV

CELL

does not rise to at least V

MIN

before the

expiration of time-out limit t

MTO

(e.g. the cell has failed

short), the bq2054 enters the Fault state. If V

MIN

achieved before expiration of the time limit, the chip be

gins fast charging.

Once in the Fault state, the bq2054 waits until V

is cycled or a new battery insertion is detected. It then starts a new charge cycle and begins the qualification process again.

bq2054

GR205401.eps

MAX

MIN

COND

MIN

REG

Current

Voltage

Qualification

Time

Phase 1 Phase 2

Fast Charge

Voltage

Current

Figure 1. bq2054 Charge Algorithm

Chip On

VCC 4.5V

Temperature

Checks On

Battery

Status?

Temperature

in Range

Temperature Out

of Range or

Thermistor Absent

Qualification Test

Current

Regulation

@ I

COND

Phase 2

V = V

REG

Fault

LED3 =1

MOD = 0

Charge

Complete

Charge

Pending

LED3 flash

MOD = 0

Phase 1 I = I

MAX

Temperature Out

of Range or

Thermistor Absent

Temperature In

Range, Return

to Original State

BAT

< V

LCO

BAT

> V

HCO

t t > t

MTO

BAT

< V

LCO

BAT

> V

HCO

Fail: t = tQT or

BAT

< V

LCO

BAT

> V

HCO

Present

LCO

< V

BAT

< V

HCO

BAT

< V

MIN

PASS: V

BAT

MIN

BAT

< V

REG

BAT

REG

Fast

Charge

SNS

> I

MIN

SNS

MIN

t t

MTO

FG205401.eps

Absent

BAT

< V

LCO

BAT > VHCO

BAT

LCO

BAT

HCO

BAT

LCO

BAT

HCO

Figure 2. bq2054 State Diagram

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

MIN

DSEL/LED

is a bi-directional pin with two functions; it 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

rises to a valid level.

2. The bq2054 leaves the Fault state.

3. The bq2054 detects battery insertion.

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

bq2054

Mode Charge Action State LED

LED

DSEL = 0

(Mode 1)

Battery absent or over-voltage fault Low Low High

Pre-charge qualification Flash Low Low

Fast charging High Low Low

Charge complete Low High Low

Charge pending (temperature out of range) X X Flash

Charging fault X X High

DSEL = 1

(Mode 2)

Battery absent or over-voltage fault Low Low High

Pre-charge qualification High High Low

Fast charge Low High Low

Charge complete High Low Low

Charge pending (temperature out of range) X X Flash

Charging fault X X High

DSEL = Float

(Mode 3)

Battery absent or over-voltage fault Low Low High

Pre-charge qualification Flash Flash Low

Fast charge: current regulation Low High Low

Fast charge: voltage regulation High High Low

Charge complete High Low Low

Charge pending (temperature out of range) X X Flash

Charging fault X X High

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

sec. low,

sec high.

Table 1. bq2054 Display Output Summary

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