TEXAS INSTRUMENTS bq2057, bq2057C, bq2057W, bq2057T Technical data

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bq2057/C/W/T

Advanced Li-Ion Linear Charge

Management IC

Features

Ideal forsingle- and dual-cell Li-Ion
packs with coke or graphite anodes

0.3V dropout voltage
AutoComp™ dynamic compensa

tion ofbattery pack’s internal im
pedance

Optional temperature-monitoring
before and during charge

Integrated voltage and current
regulation with programmable
charge-current and high- or
low-side current sensing

Integrated cell conditioning for
reviving deeply discharged cells
and minimizing heat dissipation
during initial stage ofcharge

Better than
tion accuracy

Charge status output for LED or
host processor i nterface

Automatic battery-recharge feature
Charge termination by minimum

current
Low-power sleep mode
Packaging: 8-pin SOIC, 8-pin

TSSOP

±

1% voltage regula-

General Description

The BENCHMARQ bq2057 series
advanced Li-Ion linear charge­management ICs are designed for
cost-sensitive and compact portable
electronics. They combine high-

­accuracy current and voltage

­regulation, battery conditioning,

temperature monitoring, charge
termination, charge-status indi­cation, and AutoComp charge-rate
compensation in a single 8-pin IC.

The bq2057 continuously measures
battery temperature using an exter­nal thermistor. For safety reasons,
the bq2057 inhibits charge until the
battery temperature is within
user-defined thresholds. The bq2057
then charges th e battery in three
phases: conditioning, constant cur­rent, and constant voltage. If the bat­tery voltage is below the low-voltage
threshold V
trickle-charges to condition the bat­tery. The conditioning charge rate is
set at approximately 10% of the reg­ulation current. The conditioning
current also minimizes heat dissipa­tion in t he external pass-element
during the initial stage ofcharge.

After conditioning, the bq2057 ap
plies a constant current to the bat
tery. An external sense-resistor sets
the magnitude of the current. The
sense-resistor can be on either the

, th e bq2057

MIN

low or t h e high side of th e battery
without additional components. The
constant-current phase continues
until the battery reaches th e
charge-regulation voltage.

The bq2057 then begins the con
stant-voltage phase. The accuracy of
the voltage regulation is better than

±

1% over the operating-temperature
and supply-voltage ranges. For sin
gle and dual cells with either coke or
graphite anodes, the bq2057 is of
fered in four fixed-voltage versions:

4.1V, 4.2V, 8.2V, and 8.4V. Charge
stops when the current tapers to the
charge termination threshold,
V

. The bq2057 automatically re-

TERM

starts the charge if the battery volt­age falls belowthe V

The designer also may use the
AutoComp feature to reduce charg­ing time. This proprietary technique
allows safe and dynamic compensa­tion for t h e internal impedance of
the battery pack during charge.

Available Options

Part Number

-

-

bq2057 4.1V
bq2057C 4.2V
bq2057T 8.2V

bq2057W 8.4V

threshold.

RCH

Charge

Regulation

Voltage

-

-

-

Pin Connections

SLUS025B–JANUARY2000–REVISED JUNE 2000

Pin Names

SNS Current-sense input
BAT Battery-voltage input
V
TS Temperature sense

CC

Supply voltage

input

1

STAT Charge status output
V
CC Charge control output
COMP Charge-rate

Ground input

SS

compensation input

bq2057

Pin Descriptions

SNS Current-sense input

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

BAT Battery voltage input

Voltage sense-input tied directly to the posi
tive side ofthe battery.

V

CC

TS Temperaturesenseinput

VCCsupplyinput

Input for an external battery-temperature
monitoring circuit. Connecting this input to
Vcc/2 disables th i s feature.

BAT

STAT Charge status output

Tri-state indication of charge-in-progress,
charge-complete, andtemperature fault.

-

V

SS

-

Ground input

CC Charge-control output

Source-follower output that drives a n exter

-

nal pass-transistor for current and voltage
regulation.

-

COMP Charge-rate compensation input

Sets the charge-rate compensation level. The
voltage-regulation output may be pro

­grammed to vary as a function ofthe charge
current delivered to the battery.

V

SS

V

CC

POWER

ON

RESET

CC

COMP

SNS

TS

K

COMP

V

REG

CONTROL

V

SNS

V

, V

TS1

TS2

Figure 1. Functional Block Diagram

2

BLOCK

LED

STAT

VCC

STAT

2057FBD.eps

bq2057

Sleep Mode

LED = Hi-Z

V

≤ V

BAT

MIN

NO

Current

Regulation

Phase

LED = High

Voltage

Regulation

Phase

LED = HIGH

NO

YES

YES

NO

VCC > V

BAT

YES

Temperature

Check

TS > V

TS1

TS < V

TS2

Conditioning

Phase

LED = High

I

REG

I

≤ V

BAT

10

YES

NO

Temperature

Fault

LED = Hi-Z

Charge

Complete

LED = LOW

YES

≤ V

BAT

RCH

2057OFC.eps

Figure 2. Operational Flow Chart

Functional Description

Figure 1 is a functional block diagram, Figure 2 a n oper
ational flow chart, an d Figure 3 a typical charger sche
matic forthe bq2057.

Charge Qualification and Conditioning

When power is applied, the bq2057 starts a charge-cycle
if a battery is already present or when a battery is in

NO

serted. Charge qualification is based on battery temper
ature and voltage. The bq2057 suspends charge if the
battery temperature is outside the V

­and suspends charge until the battery temperature is

­within th e allowed range. The bq2057 also checks the

TS1

to V

battery voltage. If the battery voltage is below the
low-voltage threshold V
trickle-charge to condition the battery. The conditioning
charge rate I

-

regulation current. The conditioning current also mini

is set at approximately 10% of the

COND

, th e bq2057 uses

MIN

3

TS2

-

range

-

bq2057

R

DC+

DC-

SNS

0.2Ω

0.1µF

Q1

FZT788B

R1
1kΩ

78

CC

1

SNS

3

V

CC

6

V

C2

SS

bq2057

COMP

BAT

STAT

D2

V

CC

V

CC

2

4

TS

5

D1

R2
2kΩ

R

T1

R

T2

C1

0.1µF

PACK+

PACK-

TEMP

Figure 3. Low-Dropout Single- or Dual-Cell Li-Ion Charger

Battery

2057ldc.eps

NTC

Pack

mizes heat dissipation in the external pass-element dur­ing t he initial stage ofcharge. See Figure 4 for a typical
charge-algorithm.

Current Regulation

The bq2057 regulates current while the battery-pack
voltage i s less than the regulation voltage, V
bq2057 monitors charge current a t the SNSinput by the
voltage drop across a sense-resistor, R
the battery pack. I n high-side current sensing configura
tion (Figure 5), R
pins, and in low-side sensing (Figure 6) the R

is placed between the Vcc and SNS

SNS

, in series with

SNS

placed between Vss (battery negative) and SNS (charger
ground) pins.

Charge-current feedback, applied through pin SNS,
maintains regulation around a threshold ofV
lowing formula calculates the value ofthe sense resistor:

V

SNS

SNS

=

REG

I

where I

R

is the desired charging current.

REG

SNS

. The

REG

SNS

. The fol

Voltage Monitoring and Regulation

Voltage regulation feedback is through pin BAT. This in
put is tied directly to the positive side of the battery
pack. The bq2057 monitors t he battery-pack voltage be
tween the BAT and V
four fixed-voltage versions for single- and dual-cells with

pins. The bq2057 is offered in

SS

either coke or graphite anodes: 4.1V, 4.2V, 8.2V, and

8.4V.
Other regulation voltages can be achieved by adding a

voltage divider between the positive and negative termi­nals of th e battery pack. The voltage divider presents a
scaled battery pack voltage to BAT input. (See Figures 7
and 8.) The resistor values R
divider ar e calculated bythe following equation:

R

B1

-

is

=∗

B2

R






and RB2for the voltage

B1

V

CELL



N



−

1

REG

V



where

N=Number ofcellsin series

-

V

= Desired regulation voltage pe r cell

CELL

Charge Terminationand Re-Charge

The bq2057 monitors the charging current during the
voltage-regulation phase. The bq2057 declares a “battery­complete” condition a nd terminates charge when the
current tapers off to the charge termination threshold,
V

. A new charge cycle begins when the battery volt

TERM

age falls below the

-

-

VRCH

threshold.

-

4

bq2057

I

COND

Low-Current

Conditioning

Phase

V

PACK

V

REG

I

REG

V

MIN

I

REG

=

10

Current

Regulation

Phase

V

BAT

(Shown with the optional AutoComp feature)

Voltage Regulation Phase

I

BAT

GR2057b.eps

I

FULL

I

REG

=

10

Figure 4. Typical Charge Algorithm

DC+

R

SNS

DC-

2057HSCS.eps

bq2057

1

SNS

2

BAT

3

V

CC

4

TS

COMP

CC

V

STAT

8
7
6

SS

5

Figure 5. High-Side Current Sensing

BAT+

BAT-

DC+

bq2057

DC-

1
2
3
4

SNS
BAT
V

CC

TS

COMP

CC

V

STAT

R

SNS

SS

Figure 6. Low-Side Current Sensing

5

BAT+

8
7
6
5

BAT-

2057LSCS1.eps

bq2057

DC+

R

SNS

DC-

DC+

BAT+

BAT+

R

B1

bq2057

1
2
3
4

SNS
BAT
V

CC

TS

COMP

CC

V

STAT

SS

R

8
7
6
5

B2

BAT-

2057OVDHSC.eps

DC-

bq2057

1

SNS

2

BAT

3

V

CC

4

TS

COMP

CC

V

STAT

8
7
6

SS

5

R

B1

R

B2

R

SNS

2057OVDLSC.eps

BAT-

Figure 7. Optional Voltage Divider for

Non-Standard Regulation Voltage,

(High-Side Current Sensing)

Temperature Monitoring

The bq2057 continuously monitors temperature by mea­suring the voltage between the TS and V
tive- or a positive-temperature coefficient thermistor
(NTC, PTC) and an external voltage-divider typically de­velop this voltage. (See Figure 9.) The bq2057 compares
this voltage against its internal V
to determine if charging is allowed. (See Figure 10.) The

TS1

temperature sensing circuit is immune to any fluctuation
in the V
the internal thresholds (V
V

CC

, since both the external voltage divider and

CC

.

DC+ DC+

RT1

DC-

RT2

and V

TS1

R

SNS

bq2057

1

SNS

2

BAT

3

V

CC

4

TS

pins. A nega-

SS

and V

TS2

thresholds

TS2

) are referenced to

8

COMP

7

CC

6

V

SS

5

STAT

BAT+

BAT-

Thermistor

Figure 8. Optional Voltage Divider for

Non-Standard Regulation Voltage,

(Low-Side Current Sensing)

The resistor values ofR
following equations:

ForNTCthermistors

R=

T1

R=

T2

1

SNS

2

BAT

3

V

CC

4

TS

DC-

and RT2are calculated by th e

T1

()

∗∗

TH TC

5R R

()()

∗

TC TH

3R-R

()

∗∗

TH TC

5R R

()()()

∗−∗

TC TH

2R 7R

BAT+

bq2057

COMP

V

STAT

8
7

CC

6

SS

5

R

T1

Thermistor

R

T2

BAT-

R

SNS

2057TSC.eps

High-Side Current Sensing Low-Side Current Sensing

Figure 9. Temperature Sensing Circuits

6

bq2057

V

CC

Temp Fault

V

TS2

Normal Temp Range

V

TS1

Temp Fault

V

SS

2057TSIT.eps

Figure 10. bq2057 TS Input Thresholds

ForPTC thermistors

5R R

TH TC

∗∗




R=

T1

R=

T2

()()

TH T C

3R-R

∗



()

∗∗

TH TC

5R R

()()()

∗−∗

TH TC

2R 7R






Condition STAT Pin

Battery conditioning and charging High
Charge complete Low
Temperature fault or sleep mode High-Z

Automatic Charge-Rate
Compensation

To reduce charging time, the bq2057 uses the propri
etary AutoComp technique to compensate safely for in
ternal impedance ofthe battery pack.

Figure 11 outlines th e major components of a single-cell
Li-Ion battery pack. The Li-Ion battery pack consists of
a cell, protection circuit, fuse, connector, current
sense-resistors, and some wiring. Each of these compo
nents contains some resistance. Total impedance of the
battery pack is the su m of th e minimum resistances of
all battery-pack components. Using the minimum resis­tance values reduces the odds for overcompensating.
Overcompensating may activate the safety circuit of the
battery pack.

Compensation is through input pin COMP (Figure 12).
A portion of the current-sense voltage, presented
through this pin, is scaled by a factor of K
summed with t h e regulation threshold, V
cess increases t h e output voltage to compensate for the

REG

battery pack’s internal impedance and for undesired
voltage drops i n thecircuit.

and

COMP

. This pro-

-

-

-

where RTCis the cold-temperature resistance and RTHis
the hot-temperature resistance of the thermistor, as
specified by the thermistor manufacturer.

R

or RT2can be omitted if only one temperature set

T1

ting (Hot or Cold) isrequired.
Applying a voltage between the V

oldstopin TS disables t hetemperature-sensing feature.

TS1

and V

TS2

thresh

Low-Power Mode

The bq2057 enters the sleep mode if the VCCfalls below
the voltage at the BAT input. This feature prevents
draining the battery pack during the absence ofV

.

CC

Charge Status Display

The bq2057 reports t he status of the charger on the
tri-state STAT pin. The three states include “charge in
progress, charge complete, andtemperature fault.

-

Wire

R2

FUSE

Discharge

Protection
Controller

Wire

Cell

WireWire

Charge

2057SCLIP.eps

Terminal

-

BAT+

Terminal

BAT-

Figure 11. Typical Components of a

Single-Cell Li-Ion Pack

7

bq2057

DC+

DC-

R

COMP2

R

SNS

High-Side Current Sensing

R

1
2
3
4

COMP1

SNS
BAT
V

TS

bq2057

CC

COMP

CC
V

STAT

8
7
6

SS

5

BAT+

Figure 12. AutoComp Circuits

AutoComp setup requires the following information:

Total impedance ofbattery pack (Z
Maximum charging current (I

The voltage drop V
the battery pack can then becalculated by

across the internal impedance of

Z

V

Z=ZPACK

REG

∗

I

The required compensation is then calculated using the
following equations:

V=

COMP

V

COMP

K

REG

Z

)

PACK

)

DC+

COMP2

PACK

BAT+

BAT-

2057AC.eps

is the

bq2057

1

SNS

2

BAT

3

V

CC

4

DC-

where V
is referenced to Vcc i n high-side current-sensing config-

COMP

TS

R

R

SNS

Low-Side Current Sensing

is the voltage on COMP pin. This voltage

COMP1

COMP

CC

V

STAT

8
7
6

SS

5

R

uration and to Vss for low-side sensing. V
voltage across the battery pack.

The values ofR
ing the following equation:

COMP1

V

COMP

SNS

V

and R

COMP2

R

=

COMP2

COMP1 COMP2

R+R

can be calculated us-

V

PACK=VREG

+(K

COMP

∗

V

)

COMP

8

Absolute Maximum Ratings

Symbol Parameter Min. Max. Units Notes

V

CC

V

T

T

OPR

T

STG

P

D

VCCrelative to V

VCCrelative to V

SS

SS

Operating ambient temperature -20 70
Storage temperature -40 125

-0.3 +18 V

V

-0.3

+ 0.3

CC

V

°
°

Power dissipation 300 mW

DCvoltage applied on a ny pin (ex
cluding V

CC

C
C

bq2057

-

)

DC Thresholds (T

A=TOPR

and VCC= 4.5–15V unless otherwise specified)

Symbol Parameter Rating Tolerance Unit Notes

4.10

V

REG

Voltage regulation reference

4.20

8.20

8.40

±

1%

±

1%

±

1%

±

1%

105 ±10% mV

110

V

SNS

Curren t regulation reference

±

10%

125 ±10% mV

130 ±10% mV

V For bq2057 only; seeNotes 1, 2, 3
V For bq2057C only; see Notes 1, 2, 3
V For bq2057T only; see Notes 1, 2, 3
V For bq2057W only; see Notes 1, 2, 3

For bq2057 and bq2057C only; see
Note 2

For bq2057 and bq2057C only; see

mV

Note 4
For bq2057T and bq2057W only; see

Note 2
For bq2057T and bq2057W only, see

Note 4

3.0 ±2% V For bq2057 only

V

MIN

Conditioning voltage
reference

3.1 ±2% V For bq2057C only

6.1 ±2% V For bq2057T only

6.3 ±2% V For bq2057W only

K

COMP

V

TS1

V

TS2

V

RCH

V

RCH

V

TERM

Notes:

AutoComp gain 2.2
Lower temperature threshold
Upper temperature threshold

Recharge threshold

Recharge threshold

V

V

0.3

0.6

∗
∗

REG

REG

VCC±
VCC±

- 0.1

- 0.2

±

15%
3% of V
3% of V

±2% V

±2% V

V/V See Notes 1, 5

Voltage at pin TS, relative to V

V

CC

Voltage at pin TS, relative to V

V

CC

Voltage on BAT pin, bq2057 and
bq2057C only

Voltage on BAT pin, bq2057T and
bq2057W only

Charge termination reference -14 ±10mV mV See Note 6

1. VCC=V

2. Fo r high-side current-sensing configuration

+ 0.3V to 15V

BAT

3. For low-side current sensing configuration, t he tolerance is ±1%forT

4. For low-side current-sensing configuration

=25°and ±1.2% for TA=T

A

5. 2.4 and ±15% for bq2057T and bq2057W in low-side current sensing configuration

6. Voltage at pin SNS, relative to V

forhigh-side sensing, and to VSSfor low-side sensing, 0°C≤TA≤50°

CC

SS

SS

.

OPR

C

9

bq2057

DC Electrical Characteristics (T

A=TOPR

, and VCC= 4.5 - 15V unless otherwise specified))

Symbol Parameter Min Typical Max Units Notes

V
I

CC

I

CCS

V
V

I

IH

I

SNK

V

Note:

CC

OL

OH

OLCC

Supply voltage 4.5 - 15 V
Operating current - 2 4 mA Excluding external loads

Sleep current

-36

--10

For bq2057 and bq2057C, see note

µ

A

For bq2057T and bq2057W, see note

µ

A
Output-low voltage - 0.4 0.6 V IOL= 10mA; ST AT pin
Output-high voltage VCC- 0.5 - - V IOH= 5mA; STA Tpin

BAT input, V

µ

A

SNS, COMP, and TS inputs,

µ

A

V

SNS=VCOMP=VTS

BAT=VREG

Input leakage current

--1

--5

Sink current 5 - 40 mA CC pin, no t to exceed PDspecification
CC pin output-low

voltage

V

≥

V

BAT

MIN,VBAT-VCC

- - 1.5 V

≥

0.8V, –20°C≤TA≤70°

C.

At I

SNK

(minimum)

=5V

Ordering Information

bq2057

Package Option:

SN = 8-pin narrow SOIC
TS = 8-pin TSSOP

Device:

bq2057 Advanced Li-Ion Linear Charger for One Cell (4.1V)
bq2057C Advanced Li-Ion Linear Charger for One Cell (4.2V)
bq2057T Advanced Li-Ion Linear Charger for TwoCells (8.2V)
bq2057W Advanced Li-Ion Linear Charger for TwoCells (8.4V)

10

8-Pin SOIC Narrow (SN)

bq2057

TS: 8-Pin TSSOP

8-Pin SN(0.150" SOIC

Inches Millimeters

Dimension

A 0.060 0.070 1.52 1.78

A1 0.004 0.010 0.10 0.25

B 0.013 0.020 0.33 0.51
C 0.007 0.010 0.18 0.25

D 0.185 0.200 4.70 5.08

E 0.150 0.160 3.81 4.06

e 0.045 0.055 1.14 1.40

H 0.225 0.245 5.72 6.22

L 0.015 0.035 0.38 0.89

Dimension

A - 0.043 - 1.10

A1 0.002 0.006 0.05 0.15

B 0.007 0.012 0.18 0.30

C 0.004 0.007 0.09 0.18
D 0.1 14 0.122 2.90 3.10
E 0.169 0.176 4.30 4.48

e 0.0256BSC 0.65BSC
H 0.246 0.256 6.25 6.50

Min. Max. Min. Max.

Inches Millimeters

Min. Max. Min. Max.

)

Notes:

1. Controlling dimension: millimeters. Inches shown for reference only.
2 'D' and 'E' do not include mold flash or protrusions. Mold flash or protrusions shall not exceed 0.15mm per side
3 Each lead centerline shall be located within ±0.10mm of its exact true position.

4. Leads shall be coplanar within 0.08mm at the seating plane.
5 Dimension 'B' does not include dambar protrusion. The dambar protrusion(s) shall not cause the lead width

to exceed 'B' maximum by more than 0.08mm.
6 Dimension applies to the flat section of the lead between 0.10mm and 0.25mm from the lead tip.
7 'A1' is defined as the distance from the seating plane to the lowest point of the package body (base plane).

11

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