Datasheet BQ2057SN-C1TR, BQ2057SN-C1, BQ2057PN-C1, BQ2057CTS-C1TR, BQ2057CTS-C1 Datasheet (Texas Instruments)

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Features

➤

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

➤

Dropout voltage as low as 0.3V

➤

AutoComp™ dynamic compensa

tion of battery 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 of charge

➤ Better than ±1% voltage regula-

tion accuracy

➤ Charge status output for LED or

host processor interface

➤ Automatic battery-recharge feature

➤

Charge termination by minimum current

➤

Low-power sleep mode

➤

Packaging: 8-pin SOIC, 8-pin TSSOP

General Description

The BENCHMARQ bq2057 series advanced Li-Ion linear charge-man

agement ICs are designed for cost-sensitive and compact portable electronics. They combine high-accu

racy 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 exter

nal thermistor. For safety reasons, the bq2057 inhibits charge until the battery temperature is within user-defined thresholds. The bq2057 then charges the battery in three phases: conditioning, constant current, and constant voltage. If the battery voltage is below the low-voltage threshold V

MIN

, the bq2057 trickle-charges to condition the battery. The conditioning charge rate is set at 10% of the regulation current. The conditioning current also minimizes heat dissipation in the external pass-element during the initial stage of charge.

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 low or the high side of the battery without additional components. The constant-current phase continues until the battery reaches the 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

TERM

. The bq2057 automatically restarts the charge if the battery voltage falls below the V

RCH

thresh-

old.

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

bq2057

Pin Connections

Advanced Li-Ion Linear Charge

Management IC

PN-205701.eps

8-Pin PDIP, Narrow SOIC, or TSSOP

SNS

BAT

COMP

STAT

Pin Names

SNS Current-sense input

BAT Battery-voltage input

Supply voltage

TS Temperature sense

input

STAT Charge status output

Ground input

CC Charge control output

COMP Charge-rate

compensation input

SLUS025A – JANUARY 2000 - REVISED MAY 2000

Page 2

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 of the battery.

VCCsupply input

TS Temperature sense input

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

STAT Charge status output

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

Ground input

CC Charge-control output

Source-follower output that drives an 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 of the charge current delivered to the battery.

bq2057

VCC

CONTROL

BLOCK

REG

COMP

BAT

POWER

RESET

SNS

2057FBD.eps

TS1

, V

TS2

SNS

LED

STAT

COMP

Figure 1. Functional Block Diagram

Page 3

Functional Description

Figure 1 is a functional block diagram, Figure 2 an oper

ational flow chart, and Figure 3 a typical charger sche

matic for the 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

serted. Charge qualification is based on battery temper

ature and voltage. The bq2057 suspends charge if the battery temperature is outside the V

TS1

to V

TS2

range and suspends charge until the battery temperature is within the allowed range. The bq2057 also checks the battery voltage. If the battery voltage is below the low-voltage threshold V

MIN

, the bq2057 uses trickle-charge to condition the battery. The conditioning charge rate I

COND

is set at 10% of the regulation cur

rent. The conditioning current also minimizes heat dis

bq2057

VCC > V

BAT

Temperature

Check

TS > V

TS1

TS < V

TS2

BAT

≤ V

MIN

BAT

≤ V

BAT

≤ V

RCH

Sleep Mode

LED = Hi-Z

YES

2057OFC.eps

YES

Current

Regulation

Phase

LED = High

Voltage

Regulation

Phase

LED = HIGH

Charge

Complete

LED = LOW

Temperature

Fault

LED = Hi-Z

Conditioning

Phase

LED = High

REG

Figure 2. bq2057 Operational Flow Chart

Page 4

sipation in the external pass-element during the initial stage of charge. See Figure 4 for a typical charge-algorithm.

Current Regulation

The bq2057 regulates current while the battery-pack voltage is less than the regulation voltage, V

REG

. The bq2057 monitors charge current at the SNS input by the voltage drop across a sense-resistor, R

SNS

, in series with

the battery pack. In high-side current sensing configura

tion (Figure 5), R

SNS

is placed between the Vcc and SNS

pins, and in low-side sensing (Figure 6) the R

SNS

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

Charge-current feedback, applied through pin SNS, main

tains regulation around a threshold of V

SNS

. The follow

ing formula calculates the value of the sense resistor:

SNS

V I

SNS

REG

where I

REG

is the desired charging current.

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 the battery-pack voltage be

tween the BAT and V

pins. The bq2057 is offered in

four fixed-voltage versions for single- and dual-cells with

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 the battery pack. The voltage divider presents a scaled battery pack voltage to BAT input. (See Figures 7 and 8.) The resistor values R

and RB2for the voltage

divider are calculated by the following equation:

R R

CELL

REG

=∗

 



 



− 1

where

N = Number of cells in series

CELL

= Desired regulation voltage per cell

Charge Termination and Re-Charge

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

TERM

. A new charge cycle begins when the battery volt

age falls below the

VRCH threshold.

bq2057

2057ldc.eps

PACK+

FZT788B

bq2057

Battery

Pack

NTC

0.1µF

R2 2kΩ

SNS

0.2Ω

R1 1kΩ

SNS

COMP

BAT

STAT

DC+

DC-

TEMP

PACK-

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

* Optional.

Page 5

bq2057

BAT+

BAT-

DC+

DC-

SNS

STAT

COMP

SNS

BAT

bq2057

2057HSCS.eps

Figure 5. High-Side Current Sensing

GR2057b.eps

BAT

PACK

REG

MIN

REG

Low-Current

Conditioning

Phase

Current

Regulation

Phase

Voltage Regulation Phase

(Shown with the optional AutoComp feature)

REG

COND

FULL

Figure 4. bq2057 Typical Charge Algorithm

STAT

COMP

SNS

BAT

bq2057

BAT+

BAT-

DC+

SNS

2057LSCS1.eps

DC-

Figure 6. Low-Side Current Sensing

Page 6

Temperature Monitoring

The bq2057 continuously monitors temperature by measuring the voltage between the TS and V

pins. A negative- 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

TS1

and V

TS2

thresholds to determine if charging is allowed. (See Figure 10.) The temperature sensing circuit is immune to any fluctuation in the V

, since both the external voltage divider and

the internal thresholds (V

TS1

and V

TS2

) are referenced to

The resistor values of R

and RT2are calculated by the

following equations:

For NTC thermistors

()

5R R

3R-R

TH TC

TC TH

∗∗

∗

()

()()

()

5R R

2R 7R

TH TC

TC TH

∗∗

∗−∗

bq2057

BAT+

BAT-

2057OVDHSC.eps

SNS

DC+

STAT

COMP

SNS

BAT

bq2057

DC-

Figure 7. Optional Voltage Divider for

Non-Standard Regulation Voltage,

(High-Side Current Sensing)

BAT+

BAT-

2057OVDLSC.eps

SNS

DC+

STAT

COMP

SNS

BAT

bq2057

DC-

Figure 8. Optional Voltage Divider for

Non-Standard Regulation Voltage,

(Low-Side Current Sensing)

BAT+

BAT-

Thermistor

DC+ DC+

SNS

RT2

RT1

STAT

COMP

SNS

BAT

bq2057

High-Side Current Sensing Low-Side Current Sensing

2057TSC.eps

STAT

COMP

SNS

BAT

bq2057

BAT+

BAT-

SNS

Thermistor

DC-

Figure 9. Temperature Sensing Circuits

Page 7

For PTC thermistors

()

5R R

3R-R

TH TC

∗∗

∗

 



 



()

()()

()

5R R

2R 7R

TH TC

∗∗

∗−∗

where R

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

or RT2can be omitted if only one temperature set

ting (Hot or Cold) is required.

Applying a voltage between the V

TS1

and V

TS2

thresh

olds to pin TS disables the temperature-sensing feature.

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 of V

Charge Status Display

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

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 of the battery pack.

Figure 11 outlines the 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 sum of the minimum resistances of all battery-pack components. Using the minimum resis

tance 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

COMP

and

summed with the regulation threshold, V

REG

. This process increases the output voltage to compensate for the battery pack’s internal impedance and for undesired voltage drops in the circuit.

bq2057

TS2

TS1

Temp Fault

2057TSIT.eps

Temp Fault

Normal Temp Range

Figure 10. bq2057 TS Input Thresholds

BAT-

BAT+

Wire

Terminal

Discharge

Charge

2057SCLIP.eps

Protection Controller

FUSE

Wire

Cell

WireWire

Figure 11. Typical Components of a

Single-Cell Li-Ion Pack

Page 8

AutoComp setup requires the following information:

Total impedance of battery pack (Z

PACK

)

Maximum charging current (I

REG

)

The voltage drop VZ across the internal impedance of the battery pack can then be calculated by

= Z

PACK

∗ I

REG

The required compensation is then calculated using the following equations:

COMP

PACK

= V

REG

+ (K

COMP

∗ V

COMP

)

where V

COMP

is the voltage on COMP pin. This voltage is referenced to Vcc in high-side current-sensing configuration and to Vss for low-side sensing. V

PACK

is the

voltage across the battery pack.

The values of R

COMP1

and R

COMP2

can be calculated us-

ing the following equation:

R+R

COMP

SNS

COMP2

COMP1 COMP2

bq2057

COMP1

SNS

COMP2

DC+

High-Side Current Sensing

STAT

COMP

SNS

BAT

bq2057

BAT+

BAT-

COMP1

STAT

COMP

SNS

BAT

bq2057

DC+

SNS

Low-Side Current Sensing

2057AC.eps

COMP2

DC-

Figure 12. AutoComp Circuits

Page 9

bq2057

DC Thresholds (T

A=TOPR

and VCC= 4.5–15V unless otherwise specified)

Symbol Parameter Rating Tolerance Unit Notes

REG

Voltage regulation reference

4.10

±1%

V For bq2057 only; See Note 1,2,3

4.20

±1%

V For bq2057C only; See Note 1,2,3

8.20

±1%

V For bq2057T only; See Note 1,2,3

8.40

±1%

V For bq2057W only; See Note 1,2,3

SNS

Current regulation reference

-110

±10%

= 5V, See Note 4

-115 ±10% mV V

= 9V, See Note 4

-115 ±15% mV All other V

, See Note 4

MIN

Conditioning voltage reference

3.0 ±2% V For bq2057 only

3.1 ±2% V For bq2057C only

6.0 ±2% V For bq2057T only

6.2 ±2% V For bq2057W only

COMP

AutoComp gain 2.2

±15%

V/V See Note 1

TS1

Lower temperature threshold

0.3 ∗ V

±3% of V

Voltage at pin TS, relative to V

TS2

Upper temperature threshold

0.6 ∗ V

±3% of V

Voltage at pin TS, relative to V

RCH

Recharge threshold

REG

- 0.1

±2% V

Voltage on BAT pin, bq2057 and bq2057C only

RCH

Recharge threshold

REG

- 0.2

±2% V

Voltage on BAT pin, bq2057T and bq2057W only

TERM

Charge termination reference -14 ±10mV mV See Note 4

Notes: 1. VCC= V

BAT

+ 0.3V to 15V.

2. For high-side current-sensing configuration.

3. For low-side current-sensing, the tolerance is ±1% for T

A = 25°C and ±1.2% for TA = TORR.

Absolute Maximum Ratings

Symbol Parameter Min. Max. Units Notes

VCCrelative to V

-0.3 +18 V

VCCrelative to V

-0.3

+ 0.3

DC voltage applied on any pin (ex

cluding V

)

OPR

Operating ambient temperature -20 70

°C

STG

Storage temperature -40 125

°C

Power dissipation 300 mW

4. Voltage at pin SNS, relative to VCC for high-side sensing, and to VSS for low-side sensing,

0°C <= T

A <= 50°C

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ABCDEFGHIJKLMNOPQRSTUVWXYZ!@#%^&*()_+{}|:"<>?~

Page 10

bq2057

DC Electrical Characteristics (T

= T

OPR

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

Symbol Parameter Min Typical Max Units Notes

Supply voltage 4.5 - 15 V

Operating current - 2 4 mA Excluding external loads

CCS

Sleep current

-36µAFor bq2057 and bq2057C, See note

--10µAFor bq2057T and bq2057W, See note

Output-low voltage - 0.4 0.6 V IOL= 10mA; STAT pin

Output-high voltage VCC- 0.5 - - V IOH= 5mA; STAT pin

Input leakage current

--1

µA

BAT input, V

BAT

= V

REG

--5

µA

SNS, COMP, and TS inputs, V

SNS

= V

COMP

= VTS= 5V

SNK

Sink current 5 - 40 mA CC pin, not to exceed PDspecification

OLCC

CC pin output-low voltage

- - 1.5 V

At I

SNK

(minimum)

Note: V

BAT

≥ V

MIN,VBAT -VCC

≥ 0.8V, +20°C ≤ TA≤ 70°C.

8-Pin SOIC Narrow (SN)

8-Pin SN(0.150" SOIC

)

Dimension

Inches Millimeters

Min. Max. Min. Max.

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

Page 11

bq2057

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).

Dimension

Inches Millimeters

Min. Max. Min. Max.

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 0.114 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

TS: 8-Pin TSSOP

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 Two Cells (8.2V) bq2057W Advanced Li-Ion Linear Charger for Two Cells (8.4V)

Page 12

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